SCHG:Nem s2
From Sonic Retro
Introduction
Here are my hacking notes on the Sonic 2 rom. If you use these notes I'd appreciate it if you would mention it with your hack or your utility, so that other people can find their way here. For hex editing I recommend you use a hex utility called Hex workshop, and for emulators I recommend you get both Gens and Genecyst. Genecyst may be old and kinda crap, but it has a whole heap of debug outputs that really help when it comes to seeing exactly what it's doing and when.
First of all it's very important that you understand the basics. All data stored on a computer is in the form of 1's and 0's. On a CD for example, a laser hits the surface, and if the laser bounces back and hits the lens it's a 1, and if it doesn’t it's a zero. Each 1 or 0 is called a bit, and a bit cannot have any other characters in it other that a 1 or a 0. Now the computer deals with bits in groups of 4. There are 16 possible combinations for a group of four 1's and 0's, so to make it simpler it deals with it as one value, rather than 4 (Eg. 0110 becomes 6). Now as there are 16 possible combinations for a group of 4 bits, this value to represent their values must have 16 values itself, so rather than a simple 0-9, this value is 0-F (0123456789ABCDEF). This value is called a hexadecimal value (hex value for short). Each hex value is dealt with in groups of 2, called a byte, each byte having 128 possible combinations. Now on a final output level the byte may be looked up on an ASCII table, which will convert that value into a recognisable character (Eg. a byte value of 73 becomes a lowercase s on an English ASCII table). You will practically never touch the ASCII version of the code in hacking though.
Now one important thing to realise is that as one character of hex has 16 values and a decimal (real) value only has 10, it may be necessary to convert the numbers between them from time to time. This is done with the use of a base converter (included in hex workshop). Let's say you wanted to give Sonic 50 rings. If you enter 50 as the value, you will in fact end up with 80, because that value you are entering is actually a hex value, but if you use the base converter to convert it first, you merely enter the value of 50 into the decimal box, and it will spit out a hex value of 32, which will in fact give you 50 rings in the game. Another useful utility that you will need is a hex calculator (also included in hex workshop). A hex calculator is the same as a normal calculator, but it deals with hex values rather than decimal values.
Another thing you need to know is that each level in Sonic 2 has a value assigned to it, but this value does not correspond with each level's final position in the game. Here is a list of the level values in Sonic 2:
| 00 | Emerald Hill zone |
| 04 | Metropolis zone |
| 05 | Metropolis zone act 3 |
| 06 | Wing fortress zone |
| 07 | Hill Top zone |
| 08 | Hidden Palace zone |
| 0A | Oil Ocean zone |
| 0B | Mystic Cave zone |
| 0C | Casino Night zone |
| 0D | Chemical Plant zone |
| 0E | Death Egg zone |
| 0F | Aquatic Ruin zone |
| 10 | Sky Chase zone |
One other thing you need to know is the way that the Mega Drive stores all the art. All the art that is used in the game is stored in the form of 8x8 pixel blocks. These blocks do not actually store colours at all, they actually only have one hex value per pixel. That value specifies what point on the palette line the pixel will get its colour from. The palette has 4 lines, each with 16 colours on them. Now the colours on the palette can be changed at any point during play, and some palette colours may even automatically change colour each couple of frames to make it look like the colour is flashing.
Now these 8x8 blocks are not what make up the level directly. 4 8x8 blocks are grouped together to form a 16x16 block, and it is at this point that the palette line to use for that 16x16 block is specified. The 8x8 patterns can also have their x, y, or x and y values reversed when placing them in a 16x16 block. Also it's at the 16x16 level that the collision definitions are specified. Now finally we get to a 128x128 block, and these are the things that the actual level info loads. It is made up of 64 16x16 blocks, and each block inside them can use a different palette line. You cannot place anything except a sprite or a 128x128 block directly into a level.
Now that you know all the basics, here's my breakdown:
Address listing
For the most part, there are no breaks in this list. If one address follows on directly from another on this list, it does so in the rom, with the exception of data that comes before 40000. All the compiled code that is used in the game is stored in this section, and that's a pain in the ass to sort through, so there will be many breaks there. The column on the left lists it's file location, the column in the middle contains it's name and description, and the column on the right will contain any special notes about it, such as compression format used if applicable, and number of blocks an art tile uses. The right column will also contain a link with the text further info, if that particular block requires it. That link will jump to a detailed explanation of that thing. Anything linked like that will also be listed in the contents at the top of the page.
| 0-FF | Vector table | |
| 100-200 | Header | |
| 14DE-???? | Programming to do wih decompression of art tiles to VRAM | Compiled |
| 2782-28C1 | Palette pointers | |
| 28C2 | Sega screen palette (00) | |
| 2942 | Title screen palette (01) | |
| 2962 | Unknown palette (02) | |
| 29E2 | "Sonic and Miles" screen palette (03) | |
| 2A22 | EHZ palette (04, 05, 07, 0D) | |
| 2A82 | WZ palette (06) | |
| 2AE2 | MTZ palette (08, 09) | |
| 2B42 | WFZ palette (0A) | |
| 2BA2 | HTZ palette (0B) | |
| 2C02 | HPZ palette (0C) | |
| 2C62 | HPZ underwater palette (15) | |
| 2CE2 | OOZ palette (0E) | |
| 2D42 | MCZ palette (0F) | |
| 2DA2 | CNZ palette (10) | |
| 2E02 | CPZ palette (11) | |
| 2E62 | CPZ underwater palette (16) | |
| 2EE2 | DEZ palette (12) | |
| 2F42 | ARZ palette (13) | |
| 2FA2 | ARZ underwater palette (17) | |
| 3022 | SCZ palette (14) | |
| 3082 | Unknown palette (19) | |
| 30A2 | Unknown palette (1A) | |
| 30C2 | OOZ boss palette (25) | |
| 30E2 | Menu palette (26) | |
| 3162 | Main special stage palette (18) | |
| 31C2 | Special stage 1 palette (1B) | |
| 31E2 | Special stage 2 palette (1C) | |
| 3202 | Special stage 3 palette (1D) | |
| 3222 | Special stage 4 palette (1E) | |
| 3242 | Special stage 5 palette (1F) | |
| 3262 | Special stage 6 palette (20) | |
| 3282 | Special stage 7 palette (21) | |
| 32A2 | Unknown palette (22) | |
| 32C2 | Unknown palette (23) | |
| 32E2 | Unknown palette (24) | |
| 3302 | Unknown palette (27) | |
| 3EA0-3EB0 | Music playlist for levels | Further info |
| 4948-498B | Pointers to demo file to use for levels | |
| 49E8-4A70 | Pointers to collision indexes | Further info |
| 6FC0 | ??????? (sprite) | |
| 70F0 | ??????? (sprite) | |
| 7356 | ??????? (sprite) | |
| 7A68 | Continue text (sprite) | |
| 7B82 | Sprite of sonic lying down from continue screen (sprite) | |
| 80BE | ??????? (sprite) | |
| 9454-947B | Level select level order | Further info |
| A1D6 | Cut scene at end of game (sprite) | |
| A3C8 | ??????? (sprite) | |
| A894 | ??????? (sprite) | |
| A988 | ??????? (sprite) | |
| A9F2 | ??????? (sprite) | |
| AAAE | ??????? (sprite) | |
| C054-C14F | Level size array | Further info |
| C150-C1CF | Code for initial character and screen placement | Compiled |
| C1D0-C257 | Character start location array | Further info |
| C4FC | Offset index of rasterised layer deformation | Further info |
| C51E | Unknown (possibly title screen) | Further info |
| C57E | EHZ layer deformation info | |
| C682 | Unknown (splitscreen, EHZ?) | |
| C7F2 | HTZ layer deformation info | |
| C7BA | Unknown (level value 02) | |
| C7F2 | Unknown (identical to WFZ) | |
| C82A | WFZ layer deformation info | |
| C8CA | Unknown (identical to HTZ) | |
| C964 | HTZ layer deformation info | |
| CA92 | Unknown (background fixed) | |
| CB10 | Unknown (splitscreen, background locked, no deformation) | |
| CBA0 | HPZ layer deformation info | |
| CC66 | OOZ layer deformation info | |
| CD2C | MCZ layer deformation info | |
| CE6C | Unknown (splitscreen, background free moving, but no alteration) | |
| D0C6 | CNZ layer deformation info | |
| D194 | CNZ 2 player splitscreen | |
| D27C | CPZ layer deformation info | |
| D382 | DEZ layer deformation info | |
| D4AE | ARZ layer deformation info | |
| D5DE | SCZ layer deformation info | |
| D666 | 01, 03, 09 layer deformation info | |
| F66C | ??????? (sprite) | |
| FC98 | Swinging platform from aquatic ruin zone (sprite) | |
| 10310 | ??????? (sprite) | |
| 104AC | Stationary floating platform from aquatic ruin zone (sprite) | |
| 108BC | Collapsing platform from either oil ocean zone or mystic cave zone (sprite) | |
| 10A08 | Collapsing platform from aquatic ruin zone (sprite) | |
| 111D4 | ??????? (sprite) | |
| 112F0 | ??????? (sprite) | |
| 115C4 | Stomper from MCZ (sprite) | |
| 1169A | One way barrier from chemical plant zone and DEZ (sprite) | |
| 1188C | An animal and the 100 that are given off from busting a badnick (sprite) | |
| 11DC6 | 100 points (sprite) | |
| 11F44 | A ring (sprite) | |
| 12078 | Sprite of rings spraying out from being hit by an enemy (sprite) | |
| 125E6 | ??????? (sprite) | |
| 12670 | Monitor (sprite) | |
| 12854 | Image of what was in monitor flying up like it does when you bust it (sprite) | |
| 12E18 | Flashing stars from intro (sprite) | |
| 132F0 | ??????? (sprite) | |
| 13600 | ??????? (sprite) | |
| 13C48 | Sprite for level title card (sprite) | |
| 13F74 | ??????? (sprite) | |
| 14086 | End of level result screen (sprite) | |
| 142F8-1433B | Main game level order | |
| 143C0 | End of special stage result screen (sprite) | |
| 15900 | Vertical spikes (sprite) | |
| 15CC8 | ??????? (sprite) | |
| 15D44 | ??????? (sprite) | |
| 1600C | Sprite programming pointers (one address per sprite value) | |
| 1637C | ??????? (sprite) | |
| 18888 | Red spring facing upwards (sprite) | |
| 191B8 | ??????? (sprite) | |
| 19F50 | Sonic (sprite) | |
| 1B8A4 | Tails (sprite) | |
| 1D200 | ??????? (sprite) | |
| 1D320 | ??????? (sprite) | |
| 1D8F2 | ??????? (sprite) | |
| 1D97E | ??????? (sprite) | |
| 1DD20 | ??????? (sprite) | |
| 1E0F0 | ??????? (sprite) | |
| 1F0B0 | Starpoll (sprite) | |
| 1F624 | ??????? (sprite) | |
| 1F730 | Star ball that sonic bounces off from CNZ (sprite) | |
| 1F8A8 | ??????? (sprite) | |
| 1FCDC | ??????? (sprite) | |
| 2009C | Section of pipe that tips you off from chemical plant zone (sprite) | |
| 20210 | ??????? (sprite) | |
| 2031C | Master emerald (sprite) | |
| 203AC | ??????? (sprite) | |
| 208DC | ??????? (sprite) | |
| 20B9E | ??????? (sprite) | |
| 20DEC | ??????? (sprite) | |
| 20FD2 | Big pylon thing that's in the foreground in CPZ (sprite) | |
| 21088 | An explosion of an enemy, giving off an animal and 100 points (sprite) | |
| 2115C | ??????? (sprite) | |
| 21392 | ??????? (sprite) | |
| 214C4 | Rotating cylinder in Metropolis zone (sprite) | |
| 21928 | See saw thingy from hill top zone (sprite) | |
| 21DAC | Diagonally moving lift thing from hill top zone (sprite) | |
| 22018 | ??????? (sprite) | |
| 222AC | Booster things from chemical plant zone (sprite) | |
| 22408 | ??????? (sprite) | |
| 2259C | Spin tube from chemical plant zone (sprite) | |
| 22FF8 | ??????? (sprite) | |
| 23300 | ??????? (sprite) | |
| 2351A | ??????? (sprite) | |
| 238DC | ??????? (sprite) | |
| 23AF4 | Platform that shoots up in the air from oil ocean zone (sprite) | |
| 23E40 | Spiky ball from OOZ (sprite) | |
| 24020 | Oil in OOZ (sprite) | |
| 240F8 | Strange spring from OOZ facing vertically (sprite) | |
| 24A16 | Ball sitting on strange spring from OOZ (sprite) | |
| 24DD0 | Block thingy in OOZ that launches you into the round ball things (sprite) | |
| 25244 | Thingy from oil ocean zone that you enter when flying as a ball, and it turns and throws you another direction (sprite) | |
| 25694 | Arrow shooter from aquatic ruin (sprite) | |
| 2588C | Pillar that drops it's lower part from aquatic ruin zone (sprite) | |
| 25A5A | Raising pillar from ARZ (sprite) | |
| 26104 | Sprite that makes leaves fly off when you hit it from ARZ (sprite) | |
| 26370 | Weird lever like spring from chemical plant zone and ARZ (sprite) | |
| 26634 | Thing that pops up and releases steam sideways from metropolis zone (sprite) | |
| 26920 | Twin stompers from MTZ (sprite) | |
| 26AE0 | ??????? (sprite) | |
| 26F58 | ??????? (sprite) | |
| 2715C | One of the spin tubes from MTZ (sprite) | |
| 27594 | Block that has a spike that comes out of each side sequentially from MTZ (sprite) | |
| 27794 | Floor spike from MTZ (sprite) | |
| 27884 | Nut from MTZ (sprite) | |
| 27AB0 | ??????? (sprite) | |
| 27D6C | ??????? (sprite) | |
| 28034 | ??????? (sprite) | |
| 283AC | ??????? (sprite) | |
| 285C0 | ??????? (sprite) | |
| 28BC8 | ??????? (sprite) | |
| 28DF8 | Spike block thing from MCZ (sprite) | |
| 28FF8 | ??????? (sprite) | |
| 291CC | Stairs from CPZ that move down to open the way (sprite) | |
| 293A0 | Platform that moves back and forth on top of chemicals in CPZ (sprite) | |
| 29590 | ??????? (sprite) | |
| 297E4 | Vine switch that you hang off in MCZ (sprite) | |
| 2997C | Vine that you hang off and it moves down from MCZ (sprite) | |
| 2A000 | ??????? (sprite) | |
| 2A290 | Platform that is usually swinging from ARZ (sprite) | |
| 2A4FC | 3 adjoined platforms from ARZ that rotate in a circle (sprite) | |
| 2A7B0 | Fan blowing to the left from OOZ (sprite) | |
| 2AB84 | Vertical spring from CNZ that you hold down jump on to pull back further (sprite) | |
| 2B140 | ??????? (sprite) | |
| 2B528 | Flashing blocks in CNZ that appear and disappear in a rectangular shape that you can walk across (sprite) | |
| 2B84C | ??????? (sprite) | |
| 2B8EC | Big block from casino night zone that moves back and forth (sprite) | |
| 2BA08 | Elevator going up from CNZ (sprite) | |
| 2BB6C | Poky that gives out points from CNZ (sprite) | |
| 2C448 | ??????? (sprite) | |
| 2C6AC | Block thingy in CNZ that changes colour when you hit it and gives you points, until it disappears) (sprite) | |
| 2C92C | A sprite that you can hold on to, like the rails in WFZ (sprite) | |
| 2CA14 | Octopus badnick from OOZ (sprite) | |
| 2CCC8 | Seahorse badnick from OOZ (sprite) | |
| 2D068 | Buzz bomber from EHZ (sprite) | |
| 2D394 | Shark badnick from EHZ (sprite) | |
| 2D494 | ??????? (sprite) | |
| 2D734 | ??????? (sprite) | |
| 2EF18 | ??????? (sprite) | |
| 2FC50 | ??????? (sprite) | |
| 2FCF4 | Button (sprite) | |
| 30480 | ??????? (sprite) | |
| 30FA4 | Earthquake (sprite) | |
| 318F0 | ??????? (sprite) | |
| 32288 | ??????? (sprite) | |
| 32940 | ??????? (sprite) | |
| 32F90 | ??????? (sprite) | |
| 338EC | ??????? (sprite) | |
| 340A4 | ??????? (sprite) | |
| 347EC | ??????? (sprite) | |
| 34A5C | ??????? (sprite) | |
| 34EB0 | ??????? (sprite) | |
| 34FA0 | ??????? (sprite) | |
| 353FE | ??????? (sprite) | |
| 35554 | ??????? (sprite) | |
| 35FBC | ??????? (sprite) | |
| 36924 | Blowfly enemy from ARZ (sprite) | |
| 36A76 | ??????? (sprite) | |
| 36B88 | ??????? (sprite) | |
| 36BD4 | ??????? (sprite) | |
| 36DAC | ??????? (sprite) | |
| 36F0E | ??????? (sprite) | |
| 36FE6 | ??????? (sprite) | |
| 370FE | Red circle dude from hill top zone that has lava balls circling around him that he throws at you. (sprite) | |
| 37322 | Lava snake (sprite) | |
| 373D0 | ??????? (sprite) | |
| 376E8 | ??????? (sprite) | |
| 377C8 | Bomber badnick from SCZ (sprite) | |
| 37936 | Turtle thing on the back of another larger turtle thing from SCZ (sprite) | |
| 37A06 | ??????? (sprite) | |
| 37A82 | ??????? (sprite) | |
| 37BFA | Coconuts (the badnick) from EHZ (sprite) | |
| 37E16 | Snake like badnick from MCZ that flies out from wall at you (sprite) | |
| 3800C | Crab like badnick from MTZ (sprite) | |
| 3815C | ??????? (sprite) | |
| 383B4 | Praying Mantis dude from MTZ (sprite) | |
| 384A2 | ??????? (sprite) | |
| 3873E | Glowbug from MCZ (sprite) | |
| 3899C | Exploding star from MTZ (sprite) | |
| 38AEA | ??????? (sprite) | |
| 38B86 | ??????? (sprite) | |
| 38DBA | Spider badnick from CPZ (sprite) | |
| 38F66 | ??????? (sprite) | |
| 39032 | ??????? (sprite) | |
| 39066 | ??????? (sprite) | |
| 390A2 | ??????? (sprite) | |
| 3937A | Jet badnick from SCZ (sprite) | |
| 3941C | ??????? (sprite) | |
| 39452 | ??????? (sprite) | |
| 3972C | ??????? (sprite) | |
| 3A1DC | ??????? (sprite) | |
| 3A3F8 | ??????? (sprite) | |
| 3A790 | ??????? (sprite) | |
| 3B2DE | ??????? (sprite) | |
| 3B36A | ??????? (sprite) | |
| 3B3FA | ??????? (sprite) | |
| 3B5D0 | Tilting platform from WFZ (sprite) | |
| 3B8A6 | ??????? (sprite) | |
| 3B968 | Wall turret from WFZ (sprite) | |
| 3BABA | ??????? (sprite) | |
| 3BB4C | ??????? (sprite) | |
| 3BB7C | ??????? (sprite) | |
| 3BBBC | ??????? (sprite) | |
| 3BC1C | ??????? (sprite) | |
| 3BD7A | Platform that pops in and out from WFZ (sprite) | |
| 3BEAA | ??????? (sprite) | |
| 3BF04 | ??????? (sprite) | |
| 3C0AC | Sprite that sonic hangs onto on the back of Robotnic's getaway ship at the end of WFZ (sprite) | |
| 3C328 | Rivet thing that you bust to get into the ship at the end of WFZ (sprite) | |
| 3C3D6 | ??????? (sprite) | |
| 3C442 | Laser boss guy at end of WFZ (sprite) | |
| 3CED0 | ??????? (sprite) | |
| 3D23E | Bad guy in CNZ (sprite) | |
| 3D4C8 | Death Egg (sprite) | |
| 3EAC8 | ??????? (sprite) | |
| 3F1E4 | Egg prison (sprite) | |
| 3FCE0 | Offset index of dynamic pattern and animated pattern load cue's | Double offset |
| 3FD24 | Dynamic pattern reloading for 01, 02, 03, WFZ, 09, MCZ, SCZ (empty) | |
| 3FD26 | Dynamic pattern reloading for HTZ | |
| 3FF08 | Dynamic pattern reloading for CNZ | |
| 3FF10 | Dynamic pattern reloading for CNZ (not linked in offset index, but loads CNZ stuff) | |
| 3FF24 | Dynamic pattern reloading for ARZ | |
| 3FF2C | Dynamic pattern reloading for EHZ, MTZ, MTZ3, HPZ, OOZ, CPZ, DEZ | |
| 3FF94 | EHZ animated pattern load cue (4) | |
| 3FFF8 | MTZ animated pattern load cue (3) | |
| 40038 | HTZ animated pattern load cue (4) | |
| 4009C | HPZ animated pattern load cue (2) | |
| 400C8 | OOZ animated pattern load cue (4) | |
| 4010E | CNZ animated pattern load cue (1) | |
| 40160 | Unknown animated pattern load cue (1) (mirror of CNZ load cue, but not linked in offset index) | |
| 401B2 | CPZ animated pattern load cue (0) | |
| 401C4 | DEZ animated pattern load cue (0) | |
| 401D6-????? | ARZ animated pattern load cue (3) | |
| 40350 | Offset index for mappings and properties of misc spites using animated patterns | |
| 40372 | EHZ, HTZ misc sprite mappings | |
| 403EE | MTZ misc sprite mappings | |
| 404C2 | HPZ misc sprite mappings | |
| 405B6 | OOZ misc sprite mappings | |
| 4061A | CNZ misc sprite mappings | |
| 406BE | Unknown misc sprite mappings (that damn phantom group again) | |
| 40762 | CPZ misc sprite mappings | |
| 4076E | DEZ misc sprite mappings | |
| 4077A | ARZ misc sprite mappings | |
| 407BE-407C0 | 01, 02, 03, WFZ, 09, MCZ, SCZ misc sprite mappings (empty) | |
| 4134C-41A6B | Big and small numbers used on counters in game | Uncompressed Further info |
| 41D0C-41D2D | Offset index of object debug lists | |
| 41D2E | EHZ/01/02/03/DEZ object debug lists | |
| 42AA8 | MTZ/MTZ act 3 object debug lists | |
| 41EEC | WFZ object debug lists | |
| 41FEE | HTZ object debug lists | |
| 420E8 | HPZ/OOZ object debug lists | |
| 421F2 | MCZ object debug lists | |
| 422B4 | CNZ object debug list |
Further info |
| 42376 | CPZ object debug list |
Further info |
| 42438 | ARZ object debug list |
Further info |
| 42522 | SCZ object debug list |
Further info |
| 42594-4265F | Main level load block pointers |
Further info |
| 42660-426E5 | Offset index of pattern load cue's | |
| 426E6-42D4F | Pattern load cues | |
| 42D50 | Curve and resistance mapping | |
| 42E50 | Collision array | |
| 44E50 | EHZ and HTZ primary 16x16 collision index | Compressed |
| 44F40 | EHZ and HTZ secondary 16x16 collision index | Compressed |
| 45040 | MTZ primary 16x16 collision index | Compressed |
| 45100 | OOZ primary 16x16 collision index | Compressed |
| 45200 | MCZ primary 16x16 collision index | Compressed |
| 452A0 | CNZ primary 16x16 collision index | Compressed |
| 45330 | CNZ secondary 16x16 collision index | Compressed |
| 453C0 | CPZ and DEZ primary 16x16 collision index | Compressed |
| 454E0 | CPZ and DEZ secondary 16x16 collision index | Compressed |
| 45610 | ARZ primary 16x16 collision index | Compressed |
| 45760 | ARZ secondary 16x16 collision index | Compressed |
| 458C0 | WFZ/SCZ primary 16x16 collision index | Compressed |
| 459A0 | WFZ/SCZ secondary 16x16 collision index | Compressed |
| 45A80 | Offset index of level layout's | |
| 45AC4 | EHZ act 1 level layout | Level compression |
| 45C84 | EHZ act 2 level layout | Level compression |
| 45E74 | MTZ act 1 level layout | Level compression |
| 462A4 | MTZ act 2 level layout | Level compression |
| 46684 | MTZ act 3 level layout | Level compression |
| 46B04 | WFZ level layout | Level compression |
| 46DD4 | HTZ act 1 level layout | Level compression |
| 47044 | HTZ act 2 level layout | Level compression |
| 47404 | OOZ act 1 level layout | Level compression |
| 47784 | OOZ act 2 level layout | Level compression |
| 47B24 | MCZ act 1 level layout | Level compression |
| 47D24 | MCZ act 2 level layout | Level compression |
| 47FF4 | CNZ act 1 level layout | Level compression |
| 483C4 | CNZ act 1 level layout | Level compression |
| 48774 | CPZ act 1 level layout | Level compression |
| 48A84 | CPZ act 2 level layout | Level compression |
| 48DE4 | DEZ level layout | Level compression |
| 48E94 | ARZ act 1 level layout | Level compression |
| 49264 | ARZ act 2 level layout | Level compression |
| 49634 | SCZ level layout | Level compression |
| 49714 | Animated flowers in EHZ and HTZ | Uncompressed |
| 49914 | Pulsing thing against chequered backing from EHZ | Uncompressed |
| 49A14 | Dynamically reloaded cliffs in background from HTZ | Art compression 192 blocks |
| 4A33E | Dynamically reloaded clouds in background from HTZ | Uncompressed |
| 4A73E | Spinning metal cylinder patterns in MTZ | Uncompressed |
| 4B73E | Lava patterns in MTZ and HTZ | Uncompressed |
| 4BD3E | Animated section of MTZ background | Uncompressed |
| 4BF7E | Pulsing ball in OOZ | Uncompressed |
| 4C0FE | Square rotating around ball in OOZ | Uncompressed |
| 4C4FE | Oil in OOZ | Uncompressed |
| 4D4FE | Flipping foreground section in CNZ | Uncompressed |
| 4EEFE | Bonus pictures for pokie in CNZ | Uncompressed |
| 4FAFE | Animated background section in CPZ and DEZ | Uncompressed |
| 4FCFE | Waterfall patterns from ARZ | Uncompressed |
| 50000 | Patterns for Sonic | Uncompressed |
| 64180 | Patterns for Tails | Uncompressed |
| 6FBE0 | Unknown offset index |
Further info |
| 6FD8C | Data that offset index is linking to (something to do with mappings for sonic) | |
| 714E0 | Unknown offset index | |
| 7168C | Data that offset index is linking to (something to do with mappings for sonic) |
Further info |
| 71D8E | Bubble | Art compression 32 blocks |
| 71F14 | Invincibility stars | Art compression 00, 34 blocks |
| 71FFC | Splash in water | Uncompressed |
| 7287C | Smoke from dashing | Uncompressed |
| 7393C | Supersonic stars | Art compression 00, 14 blocks |
| 739E2 | Unknown offset index | |
| 73AF8 | Data that offset index is linking to (something to do with mappings for tails) | |
| 7446C | Unknown offset index | |
| 74582 | Data that offset index is linking to (something to do with mappings for tails) | |
| 74876 | SEGA patterns | Art compression 127 blocks |
| 74F6C | Main patterns from title screen | Art compression 336 blocks |
| 7667A | Sonic and tails from title screen | Art compression 674 blocks |
| 78CBC | A few menu patterns | Art compression 10 blocks |
| 78DAC | Button | Art compression 16 blocks |
| 78E84 | Vertical spring | Art compression 00, 20 blocks |
| 78FA0 | Horizontal spring | Art compression 12 blocks |
| 7906A | Diagonal spring | Art compression 00, 32 blocks |
| 7923E | Score, Rings, Time patterns | Art compression 24 blocks |
| 79346 | Sonic lives counter | Art compression 12 blocks |
| 7945C | Ring | Art compression 00, 14 blocks |
| 79550 | Monitors and contents | Art compression 60 blocks |
| 7995C | Spikes | Art compression 8 blocks |
| 799AC | Numbers | Art compression 18 blocks |
| 79A86 | Starpoll | Art compression 00, 16 blocks |
| 79BDE | Signpost | Art compression 78 blocks |
| 7A1A0 | Signpost | Uncompressed |
| 7AB4A | Strange spring from CPZ and ARZ | Art compression 00, 28 blocks |
| 7AC9A | Long horizontal spike | Art compression 00, 8 blocks |
| 7AD16 | Bubble man, and bubbles from bubble man | Art compression 00, 37 blocks |
| 7AEE2 | Bubbles from character | Art compression 00, 10 blocks |
| 7AF82 | Countdown text for drowning | Uncompressed |
| 7B400 | Game/Time over text | Art compression 34 blocks |
| 7B592 | Explosion | Art compression 68 blocks |
| 7B946 | Miles life counter | Art compression 00, 12 blocks |
| 7BA32 | Egg prison | Art compression 49 blocks |
| 7BDBE | Image of tails in plane when sonic is on final frame at end of game | Art compression 00, 36 blocks |
| 7C0AA | Sonic continue | Art compression 12 blocks |
| 7C20C | Tails life counter | Art compression 12 blocks |
| 7C2F2 | Tails continue | Art compression 12 blocks |
| 7C43E | ASCII characters used in game | Art compression 00, 88 blocks |
| 7C9AE | 1P/2P wins text from 2P mode | Art compression 38 blocks |
| 7CD30 | Sonic/Miles animated background from options and level select menu | Uncompressed |
| 7D22C | Title card patterns | Art compression 94 blocks |
| 7D58A | Alphabet for font using large broken letters | Art compression 92 blocks |
| 7D990 | A menu box with a shadow | Art compression 21 blocks |
| 7DA10 | Pictures in level preview box in level select | Art compression 170 blocks |
| 7E86A | Unknown. More text I haven't figured out | Art compression 68 blocks |
| 7EB58 | Text for end of special stage, along with patterns for 3 emeralds. | Art compression 72 blocks |
| 7EEBE | "Perfect" text | Art compression 00, 14 blocks |
| 7EF60 | Bluebird | Art compression 00, 16 blocks |
| 7F0A2 | Squirrel | Art compression 00, 20 blocks |
| 7F206 | Mouse | Art compression 00, 20 blocks |
| 7F340 | Chicken | Art compression 16 blocks |
| 7F4A2 | Beaver | Art compression 00, 20 blocks |
| 7F5E2 | Penguin | Art compression 16 blocks |
| 7F710 | Pig | Art compression 18 blocks |
| 7F846 | Seal | Art compression 00, 14 blocks |
| 7F962 | Penguin | Art compression 00, 18 blocks |
| 7FADE | Turtle | Art compression 00, 20 blocks |
| 7FC90 | Bears | Art compression 00, 20 blocks |
| 7FDD2 | Rabbit | Art compression 00, 18 blocks |
| 7FF2A | Rivet thing that you bust to get inside ship at the end of WFZ | Art compression 00, 4 blocks |
| 7FF98 | Breakaway panels in WFZ | Art compression 15 blocks |
| 8007C | Spiked ball from OOZ | Art compression 00, 32 blocks |
| 80274 | Unknown. HPZ style shaded blocks | Art compression 6 blocks |
| 8030A | Striped blocks from CPZ | Art compression 4 blocks |
| 80376 | Oil falling into oil in OOZ | Art compression 16 blocks |
| 804F2 | Cascading oil from OOZ | Art compression 13 blocks |
| 805C0 | Ball on spring from OOZ | Art compression 20 blocks |
| 806E0 | Spinball from OOZ | Art compression 53 blocks |
| 809D0 | Collapsing platform form OOZ | Art compression 40 blocks |
| 80C64 | Diagonal and vertical weird spring from OOZ | Art compression 30 blocks |
| 80E26 | Swinging platform from OOZ | Art compression 28 blocks |
| 81048 | 4 stripy blocks from OOZ | Art compression 4 blocks |
| 810B8 | Raising platform in OOZ | Art compression 24 blocks |
| 81254 | Fan in OOZ | Art compression 30 blocks |
| 81514 | Green flame from thingy that shots platform up in OOZ | Art compression 18 blocks |
| 81600 | Patterns for appearing and disappearing string of platforms in CNZ | Art compression 00, 4 blocks |
| 81668 | Spiky ball from poky in CNZ | Art compression 00, 04 blocks |
| 816C8 | Moving cube from either CNZ and CPZ | Art compression 16 blocks |
| 817B4 | Elevator in CNZ | Art compression 4 blocks |
| 81826 | Bars from pokies in CNZ | Art compression 12 blocks |
| 81894 | Hexagonal bumper in CNZ | Art compression 6 blocks |
| 8191E | Normal round bumper from CNZ | Art compression 24 blocks |
| 81AB0 | Diagonal spring from CNZ that you pull back on | Art compression 32 blocks |
| 81C96 | Vertical red spring | Art compression 18 blocks |
| 81DCC | Weird blocks in CNZ that you hit 3 times to get rid of them | Art compression 28 blocks |
| 81EF2 | Flippers from CNZ | Art compression 52 blocks |
| 82216 | Large moving platform from CPZ | Art compression 00, 10 blocks |
| 82364 | Top of water in HPZ and CPZ | Art compression 00, 24 blocks |
| 824D4 | Booster things in CPZ | Art compression 00, 4 blocks |
| 8253C | CPZ enemy made up of a string of balls | Art compression 00, 04 blocks |
| 825AE | CPZ metal things | Art compression 33 blocks |
| 827B8 | CPZ large moving platform blocks | Art compression 4 blocks |
| 827F8 | Stripy blocks from CPZ | Art compression 8 blocks |
| 82864 | Small yellow moving platform from CPZ | Art compression 48 blocks |
| 82A46 | Moving block from CPZ | Art compression 24 blocks |
| 82C06 | Spring that covers tube in CPZ | Art compression 32 blocks |
| 82E02 | Top of water in ARZ | Art compression 00, 16 blocks |
| 82EE8 | Leaves from ARZ | Art compression 00, 07 blocks |
| 82F74 | Arrow shooter and arrow from ARZ | Art compression 00, 17 blocks |
| 830D2 | One way barrier from ARZ | Art compression 8 blocks |
| 8316A | Buzz bomber | Art compression 00, 28 blocks |
| 8336A | Octopus badnick from OOZ | Art compression 00, 58 blocks |
| 8368A | Flying badnick from OOZ | Art compression 00, 56 blocks |
| 839EA | Fish badnick from EHZ | Art compression 22 blocks |
| 83BF6 | Robotnic's main ship | Art compression 96 blocks |
| 84332 | Robotnic enemy from CPZ | Art compression 111 blocks |
| 84890 | Large explosion | Art compression 00, 100 blocks |
| 84F18 | Mini explosion | Art compression 00, 8 blocks |
| 84F96 | Unknown. Trail of smoke of some kind. | Art compression 00, 16 blocks |
| 8507C | EHZ boss | Art compression 128 blocks |
| 85868 | Chopper blades for EHZ boss | Art compression 00, 20 blocks |
| 8595C | HTZ boss | Art compression 00, 107 blocks |
| 86128 | ARZ boss | Art compression 166 blocks |
| 86B6E | MCZ boss | Art compression 204 blocks |
| 87AAC | CNZ boss | Art compression 00, 133 blocks |
| 882D6 | OOZ boss | Art compression 181 blocks |
| 88DA6 | MTZ boss | Art compression 124 blocks |
| 894E4 | Unknown | Uncompressed |
| 89534 | Blowfly from ARZ | Art compression 00, 9 blocks |
| 8970E | Grounder from ARZ | Art compression 00, 50 blocks |
| 89B9A | Fish from ARZ | Art compression 24 blocks |
| 89DEC | Lava snake from HTZ | Art compression 00, 19 blocks |
| 89FAA | Enemy with spike cone on top form HTZ | Art compression 20 blocks |
| 8A142 | Circular badnick from SCZ | Art compression 28 blocks |
| 8A362 | Turtle badnick from SCZ | Art compression 00, 57 blocks |
| 8A87A | Coconuts from EHZ | Art compression 38 blocks |
| 8AB36 | Snake like badnick from MCZ | Art compression 10 blocks |
| 8AC5E | Firefly from MCZ | Art compression 00, 20 blocks |
| 8AD80 | Praying mantis badnick from MTZ | Art compression 00, 32 blocks |
| 8B058 | Crab badnick from MCZ | Art compression 00, 36 blocks |
| 8B300 | Exploding star badnick from MTZ | Art compression 00, 15 blocks |
| 8B430 | Weird crawling badnick from CPZ | Art compression 00, 32 blocks |
| 8B6B4 | Spider badnick in CPZ | Art compression 00, 45 blocks |
| 8B9DC | Scratch from WFZ | Art compression 26 blocks |
| 8BC16 | Jet like badnick from SCZ | Art compression 00, 25 blocks |
| 8BE12 | Robotic sonic | Art compression 00, 217 blocks |
| 8CC44 | The tornado | Art compression 79 blocks |
| 8D1A0 | Wall turret from WFZ | Art compression 24 blocks |
| 8D388 | Hook on chain in WFZ | Art compression 00, 20 blocks |
| 8D540 | Retracting platform from WFZ | Art compression 54 blocks |
| 8D7D8 | Wheel for belt in WFZ | Art compression 00, 16 blocks |
| 8D96E | Moving platform in WFZ | Art compression 00, 12 blocks |
| 8DA6E | Giant unused vertical red laser in WFZ | Art compression 12 blocks |
| 8DAFC | Clouds | Art compression 00, 18 blocks |
| 8DC42 | Red horizontal laser in WFZ | Art compression 10 blocks |
| 8DCA2 | Platform that shoots sonic across from WFZ | Art compression 00, 05 blocks |
| 8DD0C | Rising platforms on belt from WFZ | Art compression 00, 12 blocks |
| 8DDF6 | Unused badnick in WFZ | Artcompression 12 blocks |
| 8DEB8 | Vertical spinning blades from WFZ | Art compression 4 blocks |
| 8DEE8 | Horizontal spinning blades from WFZ | Art compression 00, 29 blocks |
| 8E010 | Platforms that tilt in WFZ | Art compression 12 blocks |
| 8E0C4 | Thrust from Robotnic's getaway ship in WFZ | Art compression 00, 8 blocks |
| 8E138 | Laser boss from WFZ | Art compression 00, 117 blocks |
| 8E886 | Robotnic's head | Art compression 00, 24 blocks |
| 8EA5A | Robotnic | Art compression 76 blocks |
| 8EE52 | Robotnic's lower half | Art compression 28 blocks |
| 8EF96 | Window in back that Robotnic looks through in DEZ | Art compression 00, 08 blocks |
| 8F024 | Death egg | Art compression 327 blocks |
| 901A4 | Bouncer badnik from CPZ | Art compression 42 blocks |
| 90520 | Rocket thruster for tornado | Art compression 00, 26 blocks |
| 906DE-90973 | Mappings for movie sequence and images at end of game | |
| 90974 | Movie sequence at end of game | Art compression 00, 193 blocks |
| 91F3C | Final image of tornado with it and sonic facing screen | Art compression 00, 127 blocks |
| 927E0 | Mini pictures of tornado in final ending sequence | Art compression 00, 109 blocks |
| 92F0A | Mini pictures of sonic and final image of sonic | Art compression 135 blocks |
| 93848 | Mini pictures of sonic and final image of sonic in supersonic mode | Art compression 117 blocks |
| 93F3C | Final image of Tails | Art compression 181 blocks |
| 94B28 | Sonic the hedgehog 2 image at end of credits | Art compression 72 blocks |
| 94E74 | EHZ 16x16 block mappings | Compressed |
| 95C24 | EHZ/HTZ main level patterns | Compressed |
| 985A4 | HTZ 16x16 block mappings | Compressed |
| 98AB4 | HTZ pattern suppliment to EHZ level patterns | Compressed |
| 99D34 | EHZ/HTZ 128x128 block mappings | Compressed |
| 9CFD4 | MTZ 16x16 block mappings | Compressed |
| 9DB64 | MTZ main level patterns | Compressed |
| A06C4 | MTZ 128x128 block mappings | Compressed |
| A3364 | OOZ 16x16 block mappings | Compressed |
| A4204 | OOZ main level patterns | Compressed |
| A6834 | OOZ 128x128 block mappings | Compressed |
| A8D04 | MCZ 16x16 block mappings | Compressed |
| A9D74 | MCZ main level patterns | Compressed |
| AD454 | MCZ 128x128 block mappings | Compressed |
| AFFC4 | CNZ 16x16 block mappings | Compressed |
| B0894 | CNZ main level patterns | Compressed |
| B2CF4 | CNZ 128x128 block mappings | Compressed |
| B5234 | CPZ/DEZ 16x16 block mappings | Compressed |
| B6174 | CPZ/DEZ main level patterns | Compressed |
| B90F4 | CPZ/DEZ 128x128 block mappings | Compressed |
| BB944 | ARZ 16x16 block mappings | Compressed |
| BCC24 | ARZ main level patterns | Compressed |
| C1434 | ARZ 128x128 block mappings | Compressed |
| C4074 | WFZ/SCZ 16x16 block mappings | Compressed |
| C5004 | WFZ/SCZ main level patterns | Compressed |
| C7EC4 | WFZ pattern suppliment to SCZ tiles | Compressed |
| C85E4 | WFZ/SCZ 128x128 block mappings | Compressed |
| CA906-????? | ????????? (Special stage stuff) | |
| DCD68 | Background patterns for special stage | Art compression 127 blocks |
| DD48A | Sonic/Miles and number text from special stage | Art compression 62 blocks |
| DD790 | "Start" patterns in special stage | Art compression 48 blocks |
| DD8CE | Stars in special stage | Art compression 00, 37 blocks |
| DD9C8 | Unknown. Text in special stage. | Art compression 13 blocks |
| DDA7E | Ring patterns in special stage | Art compression 104 blocks |
| DDFA4 | Horizontal shadow patterns in special stage | Art compression 38 blocks |
| DE05A | Diagonal shadow patterns from special stage | Art compression 58 blocks |
| DE120 | Vertical shadow patterns in special stage | Art compression 25 blocks |
| DE188 | Explosion patterns in special stage | Art compression 00, 48 blocks |
| DE4BC | Bomb patterns in special stage | Art compression 80 blocks |
| DE8AC | Emerald patterns in special stage | Art compression 46 blocks |
| DEAF4 | Unknown. Text in special stage. | Art compression 99 blocks |
| DEEAE | Sonic and tails' animation frames from special stage | Art compression 851 blocks |
| E247E | "Tails" Patterns from special stage | Art compression 5 blocks |
| E24FE | ?????????? (affected sprites in special stage) | |
| E34EE | Unknown. looks like a really crap falling water thing. | Art compression 00, 12 blocks |
| E35F2 | ?????????? (compressed block of data to do with sprites for special stage) | Compressed |
| E427C | Data block acting as seperator | |
| E4300 | Offset index of ring location lists | |
| E4344 | EHZ act 1 ring locations | |
| E456A | EHZ act 2 ring locations | |
| E47AC | Unknown (empty) | |
| E47AE | Unknown (empty) | |
| E47B0 | Unknown (empty) | |
| E47B2 | Unknown (empty) | |
| E47B4 | Unknown (empty) | |
| E47B6 | Unknown (empty) | |
| E47B8 | MTZ act 1 ring locations | |
| E4A2A | MTZ act 2 ring locations | |
| E4C48 | MTZ act 3 ring locations | |
| E4D72 | MTZ act 4 ring locations (empty) | |
| E4D74 | HTZ act 1 ring locations | |
| E4EAA | HTZ act 2 ring locations | |
| E50E8 | HPZ act 1 ring locations | |
| E525A | HPZ act 2 ring locations (empty) | |
| E525C | Unknown (empty) | |
| E525E | Unknown (empty) | |
| E5260 | OOZ act 1 ring locations | |
| E5422 | OOZ act 2 ring locations | |
| E5598 | MCZ act 1 ring locations | |
| E570E | MCZ act 2 ring locations | |
| E5944 | CNZ act 1 ring locations | |
| E5B7E | CNZ act 2 ring locations | |
| E5E2C | CPZ act 1 ring locations | |
| E5F9E | CPZ act 2 ring locations | |
| E6150 | DEZ act 1 ring locations (empty) | |
| E6152 | DEZ act 2 ring locations (empty) | |
| E6154 | WFZ act 1 ring locations | |
| E6292 | WFZ act 2 ring locations | |
| E6294 | ARZ act 1 ring locations | |
| E642E | ARZ act 2 ring locations | |
| E6684 | SCZ act 1 ring locations | |
| E66D6 | SCZ act 2 ring locations (empty) | |
| E66D8 | Data block acting as seperator | |
| E6800 | Offset index of sprite lists | |
| E684A | EHZ act 1 sprite locations | |
| E6B7A | EHZ act 2 sprite locations | |
| E6F34 | MTZ act 1 sprite locations | |
| E73C0 | MTZ act 2 sprite locations | |
| E78EE | MTZ act 3 sprite locations | |
| E7F48 | WFZ act 1 sprite locations | |
| E82FC | WFZ act 2 sprite locations (empty) | |
| E8302 | HTZ act 1 sprite locations | |
| E8668 | HTZ act 2 sprite locations | |
| E8C80 | HPZ act 1 sprite locations | |
| E8D94 | HPZ act 2 sprite locations (empty) | |
| E8D9A | Unknown (empty) | |
| E8DA0 | OOZ act 1 sprite locations | |
| E9214 | OOZ act 2 sprite locations | |
| E968E | MCZ act 1 sprite locations | |
| E99A0 | MCZ act 2 sprite locations | |
| E9D1E | CNZ act 1 sprite locations | |
| EA3D8 | CNZ act 2 sprite locations | |
| EA9D2 | CPZ act 1 sprite locations | |
| EAD6E | CPZ act 2 sprite locations | |
| EB230 | DEZ act 1 sprite locations | |
| EB254 | DEZ act 2 sprite locations (empty) | |
| EB25A | ARZ act 1 sprite locations | |
| EB6A4 | ARZ act 2 sprite locations | |
| EBBDE | SCZ act 1 sprite locations | |
| EBD4C | SCZ act 2 sprite locations (empty) | |
| EBD52 | Unknown (empty) | |
| EBD58 | Unknown (empty) | |
| EBD5E | Unknown (empty) | |
| EBD64 | Unknown (empty) | |
| EBD66 | Data block acting as seperator | |
| EC000 | ????????? (Sound effects?) | |
| ED100 | ????????? (instruments?) | |
| F0160 | Fireball from EHZ | Art compression 20 blocks |
| F02D6 | Waterfall tiles | Art compression 24 blocks |
| F03DC | Another fireball | Art compression 00,16 blocks |
| F052A | Bridge in EHZ | Art compression 00, 8 blocks |
| F0602 | Diagonally moving lift in HTZ | Art compression 48 blocks |
| F08F6 | One way barrier from HTZ | Art compression 4 blocks |
| F096E | See-saw in HTZ | Art compression 24 blocks |
| F0B06 | Fireball from HTZ | Art compression 24 blocks |
| F0C14 | Rock from HTZ | Art compression 20 blocks |
| F0D4A | Badnick from HTZ with 4 balls of fire spinning around him | Art compression 4 blocks |
| F0DB6 | Large spinning wheel from MTZ | Art compression 120 blocks |
| F120E | Indent in large spinning wheel from MTZ | Art compression 9 blocks |
| F12B6 | Unknown. MTZ block. | Art compression 00, 8 blocks |
| F1384 | Steam from MTZ | Art compression 00, 15 blocks |
| F148E | Spike from MTZ | Art compression 00, 8 blocks |
| F1550 | Similarly shaded blocks from MTZ | Art compression 54 blocks |
| F15C6 | Lava bubble from MTZ | Art compression 00, 9 blocks |
| F167C | Unknown. A steam vent? | Art compression 00, 4 blocks |
| F16EC | Things from MTZ | Art compression 8 blocks |
| F178E | Small cog from MTZ | Art compression 00, 12 blocks |
| F1870 | Unknown. Four blocks that are all the same colour from MTZ. | Art compression 00, 4 blocks |
| F187E | Large wooden box from MCZ | Art compression 32 blocks |
| F1ABA | Collapsing platform from MCZ | Art compression 00, 26 blocks |
| F1C64 | Switch that you pull on from MCZ | Art compression 16 blocks |
| F1D5C | Vine that lowers in MCZ | Art compression 10 blocks |
| F1E06 | Unknown. A log viewed from the end | Art compression 00, 4 blocks |
| F1E8C | SEGA intro sound | 16000Hz mono 8-bit unsigned PCM raw audio |
| F8000-????? | ????????? (Midis?) |
Offset indexes
An offset index is a handy way of keeping a block of data grouped together, and also replacing a whole heap of pointers. The way it works is there is a list of two byte values, and depending on the block of data the game wants to load, it will take one of those values and add it to the starting address of the offset index. The most common usage is for every act of every level value, there is an offset that acts as the pointer to the block of data to use for it. Lets look at an example:
E6800: 004A 037A 5552 5552 5552 5552 5552 5552 0734 0BC0 10EE 10EE 1748 1AFC
Now this is the beginning of the offset index for the sprite locations. Now, can you see which values are the offset for MTZ act 2? They're 0BC0. All you had to do to get that was to take the level value for MTZ, which is 04, and count across four bytes for every value it is above 00, then across another two because it's the second act. Now we take that value and using a hex calculator, add it to the address of the offset table, which is E6800. That will give us a value of E73C0, which is the address in the rom of the MTZ act 2 sprite locations.
Also notice those 5552 values in there? Well those are for the unused level values in the game. You'll see some damn weird values put in for them in many places, and that's what causes the game to lockup in the final build of sonic 2 if you try and enter one of those levels.
There are other forms of an offset index such as the one where there's just one offset per level value, and another type that actually uses a double offset index. The first is easy enough, but a double offset index will specify two values per level, but that's not for act one and two, but rather two blocks of data to use for both acts.
Main level load block
This pointer table is what is used to load up the block mappings and main level patterns for every level in the game. Here's a breakdown of the pointer table in the S2 rom:
42594-42660: Indexed main level load block (patterns/16x16/128x128)
42594-425A0: Emerald hill zone (00)
42594: EHZ/HTZ main level patterns (95C24) [04]425A0-425AC: Unknown (01)
42598: EHZ/HTZ 16x16 block mappings (94E74) [05]
4259C: EHZ/HTZ 128x128 block mappings (99D34) [04]
425A0: EHZ/HTZ main level patterns (95C24) [06]425AC-425B8: Unknown (02)
425A4: EHZ/HTZ 16x16 block mappings (94E74) [07]
425A8: EHZ/HTZ 128x128 block mappings (99D34) [05]
425AC: EHZ/HTZ main level patterns (95C24) [08]425B8-425C4: Unknown (03)
425B0: EHZ/HTZ 16x16 block mappings (94E74) [09]
425B4: EHZ/HTZ 128x128 block mappings (99D34) [06]
425B8: EHZ/HTZ main level patterns (95C24) [0A]425C4-425D0: Metropolis zone (04)
425BC: EHZ/HTZ 16x16 block mappings (94E74) [0B]
425C0: EHZ/HTZ 128x128 block mappings (99D34) [07]
425C4: MTZ main level patterns (9DB64) [0C]425D0-425DC: Metropolis zone act 3 (05)
425C8: MTZ 16x16 block mappings (9CFD4) [0D]
425CC: MTZ 128x128 block mappings (A06C4) [08]
425E0: MTZ main level patterns (9DB64) [0C]425DC-425E8: Wing fortress zone (06)
425E4: MTZ 16x16 block mappings (9CFD4) [0D]
425E8: MTZ 128x128 block mappings (A06C4) [08]
425DC: WFZ/SCZ main level patterns [10]425E8-425F4: Hill top zone (07)
425E0: WFZ/SCZ 16x16 block mappings [11]
425E4: WFZ/SCZ 128x128 block mappings [0A]
425E8: EHZ/HTZ main level patterns (95C24) [12]425F4-42600: Hidden Palace zone (08)
425EC: EHZ/HTZ 16x16 block mappings (94E74) [13]
425F0: EHZ/HTZ 128x128 block mappings (99D34) [0B]
425F4: OOZ 16x16 block mappings (A3364) [14]42600-4260C: Unknown (09)
425F8: OOZ 16x16 block mappings (A3364) [15]
425FC: OOZ 16x16 block mappings (A3364) [0C]
42600: EHZ/HTZ main level patterns (95C24) [16]4260C-42618: Oil ocean zone (0A)
42604: EHZ/HTZ 16x16 block mappings (94E74) [17]
42608: EHZ/HTZ 128x128 block mappings (99D34) [0D]
4260C: OOZ main level patterns (A4204) [18]42618-42624: Mystic cave zone (0B)
42610: OOZ 16x16 block mappings (A3364) [19]
42614: OOZ 128x128 block mappings (A6834) [0E]
42618: MCZ main level patterns (A9D74) [1A]42624-42630: Casino night zone (0C)
4261C: MCZ 16x16 block mappings (A8D04) [1B]
42620: MCZ 128x128 block mappings (AD454) [0F]
42624: CNZ main level patterns (B0894) [1C]42630-4263C: Chemical plant zone (0D)
42628: CNZ 16x16 block mappings (AFFC4) [1D]
4262C: CNZ 128x128 block mappings (B2CF4) [10]
42630: CPZ/DEZ main level patterns (B6174) [1E]4263C-42648: Death egg zone (0E)
42634: CPZ/DEZ 16x16 block mappings (B5234) [1F]
42638: CPZ/DEZ 128x128 block mappings (B90F4) [11]
4263C: CPZ/DEZ main level patterns (B6174) [20]42648-42654: Aquatic ruin zone (0F)
42640: CPZ/DEZ 16x16 block mappings (B5234) [21]
42644: CPZ/DEZ 128x128 block mappings (B90F4) [12]
42648: CPZ/DEZ main level patterns (BCC24) [22]42654-42660: Sky chase zone (10)
4264C: CPZ/DEZ 16x16 block mappings (BB944) [23]
42650: CPZ/DEZ 128x128 block mappings (C1434) [13]
42654: WFZ/SCZ main level patterns (C5004) [24]
42658: WFZ/SCZ 16x16 block mappings (C4074) [25]
4265C: WFZ/SCZ 128x128 block mappings (C85E4) [14]
Now as you can see, these pointers specify the loading addresses in the rom for the 16x16 and 128x128 block mappings, as well as the main pattern block for that level. The main pattern block will always be loaded into the VRAM at address 0000. These loading addresses are all preceeded by a one byte value, so the address pointer only uses three bytes rather than the standard four. The value that proceeds the 128x128 block mappings specifies a value on the palette index to load for that level. For more information on the palette system, go here. The values preceeding the main level pattern and 16x16 block mapping pointers give the index numbers of the pattern load cue's to use for that level. For more information on that go here.
Pattern load cues
The pattern load cues are what loads all the pieces of art into the VRAM that are not in the main level load block. Here's a breakdown of the pattern load cues in the S2 rom:
| 00 | 426E6 | Standard block 1 (score\time\rings/lives/ring/numbers) | (3) |
| 01 | 42700 | Standard block 2 (starpoll/monitor/stars/bubbles) | (3) |
| 02 | 4271A | pattern block for level with water (explosion/stars/bubbles) | (2) |
| 03 | 4272E | game/time over (game\time over text) | (0) |
| 04 | 42736 | EHZ (waterfall/bridge/fireball/buzz bomber/coconuts/fish) | (6) |
| 05 | 4275C | EHZ (spikes/diagonal spring/horizontal\vertical spring) | (3) |
| 06 | 42776 | Miles 1up patch (Miles lives counter) | (0) |
| 07 | 4277E | Miles life counter (Miles lives counter) | (0) |
| 08 | 42786 | Tails 1up patch (Tails lives counter) | (0) |
| 09 | 4278E | Tails life counter (Tails lives counter) | (0) |
| 0A | 42796 | MTZ (Wheel/Unknown/Unknown/MSC from MTZ/steam/Unknown/MTZ spike/Badnick/starbomb) | (8) |
| 0B | 427CE | MTZ (Button/spikes/Mantis/vertical spring/horizontal spring/Unknown/Lava bubble/Cog/Unknown) | (8) |
| 0C | 42806 | WFZ (Tornado/clouds/vertical blades/horizontal blades/jet badnick/unknown/scratch/tilting platforms/tornado/clouds) | (9) |
| 0D | 42844 | WFZ (vertical blades/ horizontal blades/ unknown/ turret/ unknown/ unknown/ unknown/ unknown/ belt/ platforms/ retracting platform/ unknown/ trolley/ rivet/ unknown) | (D) |
| 0E | 4289A | HTZ (fireball/rock/conveyor/orbit badnick/unknown badnick/unknown badnick/spikes/diagonal spring/vertical spring/horizontal spring) | (9) |
| 0F | 428D8 | HTZ (lift/fireball/unknown) | (2) |
| 10 | 428EC | OOZ (green flame/raising platform/spikeball/unknown/unknown/cascading oil/unknown/unknown) | (8) |
| 11 | 42924 | OOZ (unknown/ unknown/ swinging platform/ unknown/ fan/ button/ spikes/ diagonal spring/ vertical spring/ horizontal spring/ seahorse/ octopus) | (B) |
| 12 | 4296E | MCZ (box/collapsing platform/vine switch/lowering vine/firefly/unknown badnick) | (5) |
| 13 | 42994 | MCZ (long horizontal spike/ spikes/ unknown/ other spring/ vertical spring/ horizontal spring) | (5) |
| 14 | 429BA | CNZ (unknown badnick/ moving cube/ unknown/ unknown/ unknown/ unknown/ unknown/ unknown/ unknown/ destroyable blocks) | (9) |
| 15 | 429F8 | CNZ (poky spring/vertical red spring/spikes/diagonal spring/vertical spring/horizontal spring) | (5) |
| 16 | 42A1E | CPZ (CPZ stuff/CPZ stuff/booster/moving platform/small moving platform/spring cap/water surface/moving block/CPZ platform blocks) | (8) |
| 17 | 42A56 | CPZ (unknown badnick/unknown badnick/spikes/unknown/other spring/vertical spring/horizontal spring) | (6) |
| 18 | 42A82 | DEZ (stripy blocks from CPZ) | (0) |
| 19 | 42A8A | DEZ (robotic sonic/unknown/Robotnic/Robotnic's head/Robotnic's lower half) | (4) |
| 1A | 42AAA | ARZ (one way barrier/water surface/leaves/arrow shooter) | (3) |
| 1B | 42AC4 | ARZ (shark/blowfly/grounder/bubbles/spikes/other spring/vertical spring/horizontal spring) | (7) |
| 1C | 42AF6 | SCZ (tornado) | (0) |
| 1D | 42AFE | SCZ (clouds/vertical blades/horizontal blades/jet badnick/turtle badnick/bomber) | (5) |
| 1E | 42B24 | Sonic end of level results screen (title card patterns/unknown/sonic continue/perfect text) | (3) |
| 1F | 42B3E | End of level signpost (signpost) | (0) |
| 20 | 42B46 | CPZ boss (Robotnic's main ship/CPZ boss/mini explosion/unknown/large explosion) | (4) |
| 21 | 42B66 | EHZ boss (Robotnic's main ship/EHZ boss/chopper blades/large explosion) | (3) |
| 22 | 42B80 | HTZ boss (Robotnic's main ship/HTZ boss/large explosion/unknown) | (3) |
| 23 | 42B9A | ARZ boss (Robotnic's main ship/ARZ boss/large explosion) | (2) |
| 24 | 42BAE | MCZ boss (Robtnic's main ship/MCZ boss/large explosion) | (2) |
| 25 | 42BC2 | CNZ boss (Robotnic's main ship/CNZ boss/large explosion) | (2) |
| 26 | 42BD6 | MTZ boss (Robotnic's main ship/MTZ boss/mini explosion/large explosion) | (3) |
| 27 | 42BF0 | OOZ boss (OOZ boss/large explosion) | (1) |
| 28 | 42BFE | Unknown (large explosion) | (0) |
| 29 | 42C06 | Death egg (Death egg) | (0) |
| 2A | 42C0E | EHZ animals (squirrel/blue bird) | (1) |
| 2B | 42C1C | MCZ animals (rat/chicken) | (1) |
| 2C | 42C2A | HTZ/MTZ/WFZ animals (beaver/penguin) | (1) |
| 2D | 42C38 | DEZ animals (pig/chicken) | (1) |
| 2E | 42C46 | Unknown (HPZ animals) (rat/seal) | (1) |
| 2F | 42C54 | OOZ animals (penguin/seal) | (1) |
| 30 | 42C62 | SCZ animals (turtle/chicken) | (1) |
| 31 | 42C70 | CNZ animals (bears/blue bird) | (1) |
| 32 | 42C7E | CPZ animals (rabbit/penguin) | (1) |
| 33 | 42C8C | ARZ animals (penguin/blue bird) | (1) |
| 34 | 42C9A | Special stage (emerald/unknown/special stage text/horizontal shadow/diagonal shadow/vertical shadow/explosion patterns/special stage ring/"Start"/unknown/special stage background/stars/"Tails") | (C) |
| 35 | 42CDE | Unknown (Unknown) | (0) |
| 36 | 42CF4 | Boss at end of WFZ (Laser boss from WFZ/Robotnic/Robotnic's head/Robotnic's lower half/explosion) | (4) |
| 37 | 42D12 | Tornado at end of WFZ (tornado/rocket thruster from tornado/clouds) | (2) |
| 38 | 42D26 | Egg prison (egg prison) | (0) |
| 39 | 42D2E | Normal explosion (explosion) | (0) |
| 3A | 42D36 | Tails end of level results screen (title card patterns/unknown/tails continue/perfect text) | (3) |
This pointer list has an offset index to locate the correct cue. Go here for an explanation of how this works. Now, each load cue has a two byte value before it that specifies how many addresses are in the cue, to avoid it reading too far, and going into the next cue. This value is dead simple, just enter the number of patterns on the cue in hex between the first two bytes, but you have to count 00 as 1, so if there was 16 loading addresses in the cue, you'd have 000F preceding it. After that, there are 6 bytes per load request. The first four bytes are a pointer to the art block to use, and the two bytes after that are the location in the VRAM to load them into.To change the pattern load cue's being loaded for a level, you need to change the values in the main level load block. For more information on that go here.
Collision definitions
Ok, I’m going to explain how collision works on objects that are not sprites in the sonic games. First of all forget the image that the block contains. The image has absolutely nothing to do with the collision. There's basically in invisible collision box on top of every 16x16 block that sets what's solid and what's not. This collision box has two parts to it. The main part of it is the collision array (an array is basically a table of values). The collision array stores the actual data that says that is a block is solid in certain places. It does that through 16 bytes per collision box. To understand how those 16 bytes set what's solid, imagine a 16x16 block. Now imagine that 16x16 block with the numbers 1-10 (hex) down the side starting from the bottom and going up to the top, and starting from the left and going up as it moves right along the top, so that you can give an exact location of each pixel. (eg, the top left pixel would be 10,00) Now, in this array the first two bytes define what's solid for the row of pixels on the left side of that 16x16 block. Basically the first of those two bytes says where to start making things solid, and the second byte says where to stop making them solid. So if you entered the value 0010, the first row would be solid from the very bottom of the block all the way up to the top. If you were to enter the value 020E, there would be two pixels on either side of the block that are not solid, and everything in the middle would be. The next two bytes after that are for the next row, etc. After 16 bytes the definitions for the next collision box begin.Now, to specify which blocks use which collision boxes, there are collision indexes, which give an array location for each 16x16 block. If you look at the space used by the collision array, you can divide that by 16 (the number of bytes used by each entry into the array) to give a one byte value, which represents the maximum number of collision boxes that the array can hold in the S2 platform, which is FF. Now, for each level there is at least one 16x16 collision index, and that index consists of a whole heap of array locations, one for each 16x16 block. If for example you wanted the 9th 16x16 block to use the collision box with an array location of 3E, you would give the 9th byte of the collision index for that level a value of 3E.
It is through collision indexes that the loops work in the game. It's commonly believed that there are layers, and that the sprite represented by 4 rings changes between them. This is partly true. For any levels that use multiple layers like that, there is a secondary 16x16 collision index. That object switches the 16x16 collision index in use. The pointers to these 16x16 collision indexes are stored at 49E8-4A70. The first set of pointers in this group specify the location of the primary collision index to use for each level, and the second set specify the location of the secondary collision index to use for each level.
Now just setting something as solid, doesn't give it the effect of having a slope. There's an index in the rom, which has one byte in it for each collision array location. To understand how this value works, think of two lines running parallel to each other, both with the value 0-F along them. Now, the first value of the byte gives a point on the right line, and the second value gives a point on the left line. Now imagine drawing a line between these to points. If the points are different, the resulting gradient will be taken to create the effect of a slope and the resistance going up it on the box in the corresponding collision array location.
Level layout
The level data in the S2 rom is compressed. Editing compressed data is extremely impractical, so you can either extract it first using an extraction program such as ChaoSaX-Extract, and once it's in that form refer to my savestate hacking info for information on how to edit it. Once you've finished editing it you can then use the soon to be added compression routine in ChaoSax-Extract to recompress it, and then you can place it back into the rom. If it is a larger size than the original, you will need to fiddle around with the locations and the offset index to get it back in.
Ring placement
The data for ring placement has an offset index to locate the correct group. Go here for an explanation of how this works. Now, in the rom each ring does not have to be stored individually. Instead you can place one ring, and specify that a certain number of rings come after it. The definitions for one ring takes up 4 bytes in the rom. Let's look at an example:
1234 5678
Now, in this example the ring will be placed at an x location of 1234, and a y location of 678. With that value where the 5 was entered, if the value entered is below 8, an additional ring will be placed next to the one before it for every unit that the value entered is above 0. Entering a value above 8 will place an additional ring below the one before it for each unit that the value entered is above 8. When specifying a position as the start of a group of rings, if the group is horizontal, the rings will go across to the right of that point, and if the group is vertical the rings will go down from that point. The value FFFF closes the group of ring locations, and it is essential that this is at the end of the ring locations list, or else the game will keep on reading past that point until it hits that value.
Sprite placement
Sprites are quite simple to define. It takes six bytes to define one sprite. The first two bytes are the x location of the sprite, and the next two bytes are the y location of the sprite. The 5th byte is the number on the sprite array to lookup to get the location for the function to use for the programming of that sprite, and the 6th byte is an optional declaration to use with the function for that sprite. Go here for more info on what exactly that means, and a list of all the sprites in the S2 rom.
Main level Block mappings
The block mappings in the S2 final rom are compressed. If you want to edit them you need to extract them first, edit them, and then recompress them afterwards. For more information on exactly what the block mappings do, and how to edit them, refer to the sonic 2 savestate breakdown. Note that the 16x16 block mappings in the S2 beta rom are not compressed, so if any port from the beta to the final is to be successful, those mappings will need to be compressed first.
Main level pattern blocks
Unlike the beta, the main pattern block for the levels do not use the standard art compression format, but a less complex one to allow the patterns to be loaded faster into the VRAM, and hence cut down on loading times for levels significantly. Also unlike the standard art compression format, this one has been cracked. A decompression utility such as ChaoSaX-Extract is capable of decompressing these patterns. If a port is to be done from the beta, it will be necessary to either allow the game to decompress the main pattern block into the VRAM, and then recompressing the appropriate blocks manually and putting them into the rom, or just cheat and stick these patterns on the pattern load cue. That is rather sloppy though. For information on how to edit extracted patterns, refer to the Sonic 2 savestate breakdown.
Uncompressed art
Any art that needs to be updated on the fly will not be compressed in the rom. This is because the game can't work with compressed data, and needs to extract any data it wants to use to the ram. This decompression process takes a fair bit of computation, and because of that it wouldn't be possible to create the appearance of a smooth animation using compressed data. The same reason is true as to why any data that is not loaded into the ram will always be uncompressed, because otherwise they would have to load it into the ram just to read it.
Now, for example all of the blocks for Sonic and Tails are uncompressed, because they of course need to be updated quickly. You can use basically any editing utility to edit them, but you can only change what each block looks like through this. In order to edit what blocks are placed where in each of Sonic's animation frames, you need to edit the mappings for them, and for more information on that go here. Now in their uncompressed form, you can edit them just like you would in the VRAM, so for more information on that check the sonic 2 savestate breakdown.
Mappings for Sonic/Tails
What the mappings do is they tell the game what patterns to display, and where to put them for each of the frames that the sprite has. The mappings for most sprites are contained within their function (go here for more details), but with the Sonic and Tails sprites, to allow the programmers to add a new frame easily without having to recompile the function, and hence the whole game because of the size difference, they created a separate array containing the mapping data for each frame. I haven't examined this to see how it works yet, but when I do I’ll explain the format here.
Sega intro sound
The Sega intro sound is just a 16000HZ wav sound. Opening up the rom in any sound editing program that supports raw audio with the settings listed next to the location on the list will enable you to playback the sound effect. You could also insert your own sound in the same place as long as it's at the same bitrate. The bitrate is to do with the quality of the sound. The lower it is the crappier it will sound, because that's to do with how often the output is modified. Just think of the difference between long play and short play on a VCR. Stuff recorded in long play does save space, but the quality of the recording is worse.
Art compression format
The art compression format is a very dense compression format. It's only used for art because the format relies on the data being in blocks of 64 bytes. This format is used for all the compressed art in sonic 1 and sonic 2 beta, and all the compressed art except for the main level pattern blocks in Sonic 2 and S3&K. As I said this format is very dense, and as such it requires a hell of a lot of computation to decompress. Because of this it also requires a hell of a lot of time and effort to crack. I've had a go at it, but the lightning has yet to strike. When I crack it I’ll post the format breakdown here, and create a simple program to decompress it, but until then it is impossible to directly edit any art using this format. The porting of a compressed block of art is simple though, so if you want to transfer beta art to the final, you can just tack it onto the end and enter the pointer into the pattern load cue of the level or event you want it to appear at, along with a VRAM location to load it into. Go here for more information on that.
Dynamic pattern reloading
Dynamic pattern reloading is a method of loading patterns into the VRAM, but unlike the other methods, this one has no limitations, because it uses actual programmed code. Basically this is here for any effects to do with patterns changing in game that isn't posible using the normal load cue system, like the hills in the background of HTZ where the patterns to display are determined by the position of the screen. Because the programming for it is in the form of compiled code, direct editing of it is not possible.
Animated pattern load cue's
Animated patterns require the art they are working with to be in an uncompressed form, so if you are attempting to make an animated pattern, make sure the art is uncompressed or it won't work. Now, the length of each load request on the cue varies depending on the animation. The first byte specifies a value that will determine how often to switch frames in the animation. If you use this value you will not be able to specify a frame as having a different duration to another. Setting this to FF will disable automatic frame control and allow the user to input a manual duration for each frame. This will mean that for every frame the user wants in the animation, they have to allow another byte at the end of the load request. If you want automatic pattern control, which you would use if you want all the animations frames to have the same duration. Just enter how many screen refreshes to wait until the next frame of the animation is displayed. Bytes 2,3, and 4 are the address in the rom to load the patterns from. Bytes 5 and 6 are the location in VRAM to load the patterns into. Byte 7 is the number of frames the animation has, and byte 8 is the number of spaces in VRAM to use for each frame. The function of the bytes beyond this point depend on whether or not automatic frame control is enabled, so refer to appropriate section below.
With automatic frame control:
One byte per frame of animation. This byte simply specifies the image to use for each frame of the animation. Based on the loading address entered, this value is the offset in 8x8 blocks to load each frame from in the rom. So if for example you were dealing with an animation that had 4 8x8 blocks per frame, and there were 4 frames of that, and you wanted it to display each frame one by one, you would enter the value 0004 080C.
Without automatic frame control:
Two bytes per frame of animation. The first byte is the offset of blocks in the file to load the animation frame from. This byte simply specifies the image to use for each frame of the animation. Based on the loading address entered, this value is the offset in 8x8 blocks to load each frame from in the rom. The second byte is the number of screen refreshes to keep that image loaded for, before going on to the next animation frame.
Misc sprite definitions
It looks like there are some sprites that get thier mappings and whatnot from this index, so they can reuse just a couple of sprites for some of the the miscellaneous objects in a level that the character doesn't actually interact with, but those objects can be completely different from one level to the next. A handy way of avioding programming each one individually, and thus saving a hell of a lot of space. As for how to edit them, well I haven't looked at that yet, but when I do i'll post an explination of the format here.
Rasterised layer deformation
Raster effects are simply effects to do with deformation of an image based on lines of pixels. In Sonic 2, these effects are used to create the movement effects for the backgrounds of all the levels, as well as the 2 player splitscreen effect. Because the programming for these effects are stored in the form of compiled code, you'll have to learn 68K ASM in order to edit them. Switching between levels is easy enough though, just change the corresponding value on the preceeding offset index to link to the effect you wish to use.
Palettes
All the main palettes used in the game are linked in a pointer table at 294E. In this pointer table there are 8 bytes per palette. The first four simply give a location in the rom for the data to load. The fifth and sixth bytes give the location in the system ram to load the data into, and the seventh and eighth bytes give the number of bytes being loaded. Here's a palette pointer:
0000 2942 FB20 0007
Now in this case the palette is being loaded from 00002942 in the rom into the beginning of the second above water palette row (FB20), and it's loading 4 colours (0007). Here's a listing of the palette pointers in the S2 rom:
| 00 | 2782 | SEGA screen palette (28C2) |
| 01 | 278A | Title screen palette (2942) |
| 02 | 2792 | Unknown palette (2962) |
| 03 | 279A | "Sonic and Miles" screen palette (29E2) |
| 04 | 27A2 | EHZ palete (2A22) |
| 05 | 27AA | Level value 01 palette (2A22) |
| 06 | 27B2 | WZ palette (2A82) |
| 07 | 27BA | Level value 03 palette (2A22) |
| 08 | 27C2 | MTZ palette (2AE2) |
| 09 | 27CA | MTZ act 3 palette (2AE2) |
| 0A | 27D2 | WFZ palette (2B42) |
| 0B | 27DA | HTZ palette (2BA2) |
| 0C | 27E2 | HPZ palette (2C02) |
| 0D | 27EA | Level value 09 (2A22) |
| 0E | 27F2 | OOZ palette (2CE2) |
| 0F | 27FA | MCZ palette (2D42) |
| 10 | 2802 | CNZ palette (2DA2) |
| 11 | 280A | CPZ palette (2E02) |
| 12 | 2812 | DEZ palette (2EE2) |
| 13 | 281A | ARZ palette (2F42) |
| 14 | 2822 | SCZ palette (3022) |
| 15 | 282A | HPZ underwater palette (2C62) |
| 16 | 2832 | CPZ underwater palette (2E62) |
| 17 | 283A | ARZ underwater palette (2FA2) |
| 18 | 2842 | Main special stage palette (3162) |
| 19 | 284A | Unknown palette (3082) |
| 1A | 2852 | Unknown palette (30A2) |
| 1B | 285A | Special stage 1 palette (31C2) |
| 1C | 2862 | Special stage 2 palette (31E2) |
| 1D | 286A | Special stage 3 palette (3202) |
| 1E | 2872 | Special stage 4 palette (3222) |
| 1F | 287A | Special stage 5 palette (3242) |
| 20 | 2882 | Special stage 6 palette (3262) |
| 21 | 288A | Special stage 7 palette (3282) |
| 22 | 2892 | Unknown palette (32A2) |
| 23 | 289A | Unknown palette (32C2) |
| 24 | 28A2 | Unknown palette (32E2) |
| 25 | 28AA | OOZ boss palette (30C2) |
| 26 | 28B2 | Menu palette (30E2) |
| 27 | 28BA | Unknown palette (3302) |
To change the palette being loaded for each level, you need to change the palette index number in the main level load block. For more information on that go here. The palettes themeslves are very easy to modify as they are all uncompressed in the rom. Refer to the savestate hacking documents for information on how to edit palettes.
Level size array
All the sizes of the levels are stored in a simple array, and can be easily modified to change the boundaries of the level. This array is located at C054, and for each act there are four values. The first gives the X start location of the level, and the second gives the X end location of the level. Likewise the third value gives the Y start location of the level, and the fourth gives the Y end location of the level.
Character start location array
The start location for the characers and the camera for each level are stored in this array at address C1D0. It couldn't be any simpler to modify, there's just two values per act, the first being the X location, and the second being the Y location.
Music playlist for levels
This is actually part of a sub in the code, but it's editable all the same. Pretty simple, just one byte per level. That one byte is the value of the song you wish to play. You must enter the value in the form in which it is displayed in the beta version, which is with 80 as the starting value, not 00 as it is displayed in the final. You'll notice with the value for death egg, it's 08 not 88, which is why there's no sound in the level.
Level order
There are several different sections in the game to do with the order of levels. The first one is the one that determins which level the game loads when someone finishes a level. The second one is the one which determins which level to load when you select a level from the level select menu. The level select one is easy to modify, just enter the level value followed by an act number for each of the levels you want to load, in the order you want them to be loaded. For a list of the level values for all the different stages, look at the beginning of the introduction to this page. Note that if you load the same level into the level order twice, when you link to it via the level select, it will continue the sequence from the last one in the list, not the first.