Sonic the Hedgehog 2 (Master System)

SCHG: Sonic 2 (Master System)
Main Article
Art Editing
Editing Art Palettes Uncompressed Art Compressed
Level Editing
Editing Levels Level Headers 32x32 MetaTiles Level Layout
Object Editing
Editing Objects Object Layout Object Types
Music Editing
Editing Music Driver Technical Info Module Format

Contributors

• Ambil
• Dr. Eggfan
• Glitch
• Hivebrain
• Rolken

ROM contents

Offset	Description
A4C-DEA	Level select text (plain ASCII format)
E1C-E4B	Level select level pointers
28F0	Pointers for title card mappings (16-bit, little endian)
2904-2FA7	Mappings for title cards & act results screens
55E5	Pointers for level headers (16-bit, little endian)
5635-585A	Level headers
10000	Uncompressed art - Sonic
13800	Compressed Art - bubble (ALZ)
13930	Compressed Art - jumping pig enemy (GMZ)
13BD0	Compressed Art - small yellow numbers (unused)
13CF8	Compressed Art - spinning turtle enemy (SHZ/SEZ/CEZ)
14000	Uncompressed art - Sonic gliding (SHZ)
15E00	Uncompressed art - Sonic riding a minecart (UGZ/GMZ)
18000	Uncompressed art - Sonic runnning round a loop (ALZ/GHZ)
1BC00	Compressed Art - spinning wheel (CEZ)
1BE60	Compressed Art - block (CEZ)
1C000	Compressed Art - numbers, lives icon
1C2CA	Compressed Art - collected ring sparkles
1C306	Compressed Art - invincibility sparkles
1C332	Compressed Art - explosion
1C462	Compressed Art - monitor (generic)
1C608	Uncompressed art - monitors (specific)
1CCC8	Compressed Art - rings (dropped when Sonic gets hit)
1CE98	Compressed Art - moving platform (GHZ)
1CF92	Compressed Art - glider (SHZ)
1D20E	Uncompressed art - prison capsule
1DACE	Uncompressed art - animals
1E0CE	Compressed Art - cloud & tree from scrolling text on title cards
1E124	Uncompressed art - end of act signpost
1EDA4	Compressed Art - minecart (UGZ/GMZ)
1EE48	Uncompressed art - minecart wheel (UGZ/GMZ)
1EEC8	Compressed Art - minecart wheel (UGZ/GMZ)
1F040	Compressed Art - broken minecart (UGZ/GMZ)
1F0EA	Uncompressed art - Silver Sonic (SEZ)
1F96A	Compressed Art - log (SHZ)
1F9B4	Compressed Art - moving platform (SHZ)
1FAB4	Empty
20000	Compressed Art - circle & floor from intro sequence
206A0	Compressed Art - beta title screen (unused)
213B0	32x32 mappings - intro sequence
216E0	32x32 mappings - title screen
21A32	Level layout - intro sequence (uncompressed)
21AB2	Level layout - title screen (uncompressed)
21B32	Uncompressed art - mini Sonic from intro sequence
22832	Compressed Art - scenery from intro sequence
229A2	Compressed Art - Sonic's hand from title screen
22C32	Compressed Art - Tails' face from title screen
22DA2	Mappings for title screen
2307C	Unknown
23C72	Empty
24000	Code
2411F	Palette - unknown (4 shades of grey)
2412F	Palette - unknown
2413F	Palette - unknown
2414F	Palette - title cards
2415F	Palette - Sonic (GHZ)
2416F	Palette - Sonic (SHZ1/3)
2417F	Palette - Sonic (SHZ2)
2418F	Palette - Sonic (ALZ1/3)
2419F	Palette - Sonic (ALZ2)
241AF	Palette - Sonic (UGZ)
241BF	Palette - Sonic (GMZ)
241CF	Palette - Sonic (SEZ)
241DF	Palette - Sonic (CEZ1/2)
241EF	Palette - Sonic (CEZ3)
241FF	Palette - UGZ
2420F	Palette - SHZ1/3
2421F	Palette - SHZ2
2422F	Palette - ALZ1/3
2423F	Palette - ALZ2
2424F	Palette - GHZ
2425F	Palette - GMZ
2426F	Palette - SEZ
2427F	Palette - CEZ1/2
2428F	Palette - CEZ3
2429F	Palette - intro sequence
242AF	Palette - title screen
242BF	Palette - intro sequence
242CF	Palette - title screen
242DF	Palette - unknown
242EF	Palettes (7) - title cards (UGZ, SHZ, ALZ, GHZ, GMZ, SEZ, CEZ)
2435F	Palette - unknown
2436F	Palette - Sonic (ending)
2437F	Palette - unknown
2438F	Palettes (8) - ending (gradually changes from day to night)
2440F	Palette - blank
2441F	Loop XY motion data (ALZ/GHZ)
24D1E	Compressed Art - level select text
2511E	Compressed Art - text from title cards
260A4	Compressed Art - UGZ level tiles
270DC	Compressed Art - yellow bird (SHZ)
2715C	Compressed Art - spears (ALZ)
2724E	Compressed Art - moving platform (GMZ)
2724E	Compressed Art - moving platform (SEZ)
273E8	Compressed Art - newtron (UGZ/SHZ/GHZ)
27654	Compressed Art - bomb enemy (GMZ/SEZ)
27782	Compressed Art - moving platform (UGZ)
27870	Compressed Art - crab (UGZ/ALZ/GHZ/SEZ/CEZ)
27B90	Compressed Art - splash (ALZ)
27BE0	Compressed Art - water (ALZ)
27C10	Compressed Art - falling spike (UGZ)
27CB0	Compressed Art - falling spike (GMZ)
27D50	Compressed Art - bubble (ALZ)
27E51	Empty
28000	Compressed Art - SHZ1/3 level tiles
291DC	Compressed Art - SHZ2 level tiles
2A2AC	Compressed Art - GMZ level tiles
2B2E2	Compressed Art - text from ending sequence
2B812	Empty
2C000	32x32 mappings - SHZ1/3
2D8C0	32x32 mappings - SHZ2
2F080	Level layout - CEZ1 (compressed)
2FA48	Empty
30000	32x32 mappings - GHZ
316C0	32x32 mappings - ALZ
32F80	Level layout - SHZ3 (compressed)
33716	Level layout - GMZ3 (compressed)
34000	Level layout - GHZ1 (compressed)
34C6B	Level layout - GHZ2 (compressed)
35884	Level layout - GHZ3 (compressed)
36429	Level layout - SHZ1 (compressed)
370D8	Level layout - SHZ2 (compressed)
38000	Level layout - ALZ1 (compressed)
38F68	Level layout - ALZ2 (compressed)
39DFF	Level layout - ALZ3 (compressed)
3ADBB	Level layout - UGZ1 (compressed)
3C000	32x32 mappings - ALZ2
3DD80	32x32 mappings - UGZ
3F380	Compressed Art - "Game Over" text
3F75A	Compressed Art - numbers 0 to 9 in scrolling GHZ style
3FB7E	Mappings for Game Over screen
3FC5E	Empty
40000	Uncompressed art - Sonic (mirrored)
43680	Compressed Art - little wavy lines (?)
436C0	Compressed Art - fireball (UGZ)
43722	Compressed Art - mini flame (UGZ)
43740	Compressed Art - lobster enemy (ALZ)
439A0	Compressed Art - burrobot (GMZ)
43C82	Compressed Art - moto bug (UGZ/GHZ)
43E28	Compressed Art - fish enemy (CEZ)
43EDA	Empty
44000	Uncompressed art - Sonic gliding (mirrored)
45E00	Uncompressed art - Sonic riding a minecart (mirrored)
48000	Uncompressed art - Sonic running round a loop (mirrored)
4BC00	Compressed Art - block (SEZ)
4BC80	Compressed Art - moving platform (CEZ)
4BD46	Compressed Art - levitating spiked rock (CEZ)
4C000	Level layout - GMZ1 (compressed)
4CC68	Level layout - GMZ2 (compressed)
4DA91	Level layout - SEZ1 (compressed)
4E9C9	Level layout - SEZ2 (compressed)
4F76E	Compressed Art - Tails & Eggman from intro sequence
4FC2A	Empty
50000	Compressed Art - SEZ1/3 level tiles
5102A	Compressed Art - SEZ2 level tiles
52102	Uncompressed art - UGZ boss
52E42	Compressed Art - "END" from ending sequence
53002	Compressed Art - Tails running in ending sequence
53850	Compressed Art - Tails looking up in ending sequence
53960	Uncompressed art - chaos emeralds
54000	Compressed Art - ALZ1/3 level tiles
550F0	Compressed Art - ALZ2 level tiles
56116	Compressed Art - CEZ1/2 level tiles
56E7E	Compressed Art - CEZ3 level tiles
58000	32x32 mappings - GMZ
59960	32x32 mappings - SEZ1/3
5AF20	32x32 mappings - ending sequence / original GHZ
5B900	Empty
5C000	32x32 mappings - SEZ2
5D760	32x32 mappings - CEZ3
5E000	Compressed Art - GHZ level tiles
5F11B	Level layout - UGZ2 (compressed)
60000	32x32 mappings - CEZ1/2
61600	Compressed Art - title screen
6299A	Compressed Art - Eggman final boss (CEZ3)
6339C	Compressed Art - cloud (CEZ3)
633CC	Empty
64000	Compressed Art - UGZ title card pic
649A0	Compressed Art - SHZ title card pic
65410	Compressed Art - ALZ title card pic
65DC0	Compressed Art - GHZ title card pic
66446	Compressed Art - GMZ title card pic
66C26	Compressed Art - SEZ title card pic
670A6	Compressed Art - CEZ title card pic
67806	Mappings for title card pics
67F06	Empty
68000	Uncompressed art - GMZ boss
68980	Uncompressed art - SHZ boss
69740	Uncompressed art - ALZ boss
6A0C0	Uncompressed art - GHZ boss
6B340	Compressed Art - rock (SHZ)
6B460	Compressed Art - fragment of a smashed block (all zones)
6B4EA	Uncompressed art - Tails (CEZ3)
6C000	Level layout - UGZ3 (compressed)
6C6D3	Level layout - SEZ3 (compressed)
6D1F5	Level layout - CEZ2 (compressed)
6DE81	Level layout - CEZ3 (compressed)
6DFD7	Level layout - good ending sequence (compressed)
6E151	Level layout - bad ending sequence (compressed)
6E2C2	Compressed Art - original GHZ level tiles from ending sequence
6F719	Empty
70000	Unknown
75C00	Uncompressed art - rings (UGZ)
75F00	Uncompressed art - rings (SHZ1/3)
76200	Uncompressed art - rings (SHZ2)
76500	Uncompressed art - rings (ALZ)
76800	Uncompressed art - rings (GHZ)
76B00	Uncompressed art - rings (GMZ)
76E00	Uncompressed art - rings (SEZ)
77100	Uncompressed art - rings (CEZ)
77400	Unknown
77552	Credits (plain ASCII format)
77732	Empty
78000	Unknown
78135	Pointers for sprite layouts (16-bit, little endian)
78173	Sprite layout - UGZ1
782C1	Sprite layout - UGZ2
7840F	Sprite layout - UGZ3
7848E	Sprite layout - SHZ1
784E9	Sprite layout - SHZ2
78568	Sprite layout - SHZ3
78584	Sprite layout - ALZ1
78666	Sprite layout - ALZ2
787BD	Sprite layout - ALZ3
787F4	Sprite layout - GHZ1
788C4	Sprite layout - GHZ2
78970	Sprite layout - GHZ3
78983	Sprite layout - GMZ1
78A4A	Sprite layout - GMZ2
78AFF	Sprite layout - GMZ3
78B24	Sprite layout - SEZ1
78BE2	Sprite layout - SEZ2
78C7C	Sprite layout - SEZ3
78C8F	Sprite layout - CEZ1
78D20	Sprite layout - CEZ2
78D8D	Sprite layout - CEZ3
78D97	Unknown
7AF41-7AF49	Cycling palette - UGZ lava
7AF4A-7AF52	Cycling palette - SHZ2 rain
7AF53-7AF5B	Cycling palette - ALZ water
7AF5C-7AF64	Cycling palette - GMZ wheels and conveyor belts
7AF9F-7AFCE	Cycling palette - CEZ3 lightning

Level select pointers

The pointers define which level the game goes to for each item on the level select. Each pointer consists of two bytes: one for the zone number, and one for the act number. The level numbers are as follows:

Value	Zone
00??	Underground
01??	Sky High
02??	Aqua Lake
03??	Green Hills
04??	Gimmick Mt.
05??	Scrambled Egg
06??	Crystal Egg
0700	Bad Ending Sequence
0701	Good Ending Sequence
0900	Intro Sequence
0901	Title Screen

The act numbers are just 00, 01 and 02. There are a total of 18 entries in the pointer array.

Title card mappings

The title cards are built up with rows of 8x8 tiles. Mappings define which tiles are pulled from the VRAM and displayed on the screen. Each 8x8 tile is given a 2-byte, little endian value based on where it appears in the VRAM:

So, the letter A would mapped like so:

0111	0211
0C11	0D11

Spaces not containing any letters are 7011. Here are the ROM addresses for each title card:

Offset	Level
2904	GREEN HILLS
298C	ZONE
29C4	AQUA LAKE
2A34	UNDERGROUND
2AA4	SKY HIGH
2B14	GIMMICK MT.
2B84	MOUNTAIN
2BF4	SCRAMBLED EGG
2C64	CRYSTAL EGG
2CE4	SONIC HAS
2D54	PASSED
2D98	RING
2DAC	TIME
2DC0	SCORE
2DD6	100X
2DE5	00
2DF6	00
2E04	ACT 1
2E90	ACT 2
2F1C	ACT 3

Loop XY motion data

When Sonic hits a loop in either Aqua Lake or Green Hills Zone, you're momentarily unable to control him. The loop motion data determines how Sonic moves vertically and horizontally when he reaches a loop. By default, he moves in a large circle. Modifying the loop data could allow Sonic to move around virtually any shape.

Little endian things

This means 1234 becomes 3412, and 5500 becomes 0055. It's a feature of Master System ROMs which makes hacking them slightly more confusing. Pointers have to be read backwards.