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[[Sonic Community Hacking Guide|Back to SCHG main page]]
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{{SCHG S1}}
 +
This is the '''[[Sonic Community Hacking Guide]] for ''[[Sonic the Hedgehog (16-bit)|Sonic the Hedgehog]]'''''. Originally based on [[User:Nemesis|Nemesis]] and [[User:Saxman|saxman]]'s guides, this document has grown to outclass those two documents in most ways, and is now preferred over the original guides (which were written three or four years ago with limited knowledge of the game's code). This is due to the updating of those documents to give them a living, breathing nature.
  
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==ROM Hacking==
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==Contributors==
 +
(In alphabetical order; if you are a contributor and have worked on a specific part of the guide, feel free to note that.)
  
 +
* [[User:Aurochs|Aurochs]]
 +
* [[User:Hayate|Hayate]]
 +
* [[User:Hivebrain|Hivebrain]]
 +
* [[User:KingofHarts|KingofHarts]]
 +
* [[User:Scarred Sun|Scarred Sun]]
 +
* [[User:SMTP|SMTP]]
 +
* [[User:Tweaker|Tweaker]]
 +
* [[User:Upthorn|Upthorn]]
  
  
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===Art Editing===
 
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There are several different tools that can be used to edit art besides the hex editor. [[SonED]] is probably the best tool to use for editing level art, and can also be used on palettes. [[HivePal]] is also a great tool for editing palettes. [[Sonik Sprite]] is useful for editing uncompressed art; it gets its name from its ability to edit Sonic's sprites. [[LOst Library]] is most likely the best choice for editing compressed art in the [[Nemesis compression|Nemesis format]].
 
  
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If, however, you still want to do it yourself, your best bet is to download the Sonic 1 Split disassembly. Decompress the archive into a new folder, and place your S1 ROM, ''in binary format and named "S1.bin"'', in that folder. Run the batch file "split.bat". This will split up all the art into its own binary files, which you can then decompress and edit. When you're done, run "combine.bat".
 
  
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====Uncompressed Art Locations====
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==References==
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Most of this information was taken from [[SCHG:Nem_s1|Nemesis's guide]]. Please excuse any mistakes or misunderstandings, as that guide wasn't exactly well-written. A description is written in parentheses after the original name if I deem it necessary; if I don't know what it is, "Unknown" appears in that place. Please correct this if you know. It doesn't list the number of blocks taken up, so if you know, put it in. Otherwise, I'll find out eventually.
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<references />
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====Uncompressed Art Locations====
 
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{| border="1"
 
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! Offset||Description||# of blocks
 
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|-
 
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! colspan="3" | Zone Independent
 
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|-
 
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|$1CADA
 
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|Numbers used on counters in game
 
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|?
 
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|-
 
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|$21AFE
 
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|Sonic
 
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|?
 
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|-
 
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|$6A324
 
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|Giant Ring
 
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|?
 
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|-
 
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! colspan="3" | Green Hill Zone
 
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|-
 
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|$66AD6
 
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|Waterfall tiles
 
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|?
 
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|-
 
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|$66CD6
 
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|Flower with pointy petals
 
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|?
 
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|-
 
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|$670D6
 
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|Flower with curved petals
 
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|?
 
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|-
 
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! colspan="3" | Marble Zone
 
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|-
 
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|$6755A
 
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|Lava surface
 
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|?
 
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|-
 
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|$67836
 
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|Lava
 
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|?
 
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|-
 
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|$67E56
 
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|Flame torch against stone
 
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|?
 
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|-
 
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! colspan="3" | Scrap Brain Zone
 
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|-
 
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|$68156
 
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|Steam in background
 
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|?
 
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|}
 
  
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====Compressed Art Locations - Nemesis====
 
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See [[SCHG:Sonic the Hedgehog/Nemesis Compressed Art]].
 
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====Compressed Art Locations - [[Kosinski compression|Kosinski format]]====
 
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*'''$3DCF2''' - GHZ main level patterns
 
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*'''$414D4''' - LZ main level patterns
 
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*'''$46016''' - MZ main level patterns
 
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*'''$4A7FE''' - SLZ main level patterns
 
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*'''$510F0''' - SYZ main level patterns
 
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*'''$57A66''' - SBZ main level patterns
 
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====Palette Locations====
 
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Usually, it's not really necessary to edit a palette in hex. Palette editors give you instant feedback for each RGB value, and the palette can be easily saved as a separate binary and reimported into the ROM. However, it is sometimes desireable or necessary to do it in hex, and it can't hurt to know how it's done.
 
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These are the ROM offsets of the palettes in Sonic 1, as listed by [[HivePal]]:
 
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{| border="1"
 
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! Name||Offset
 
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|-
 
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|Sega Logo (Background)
 
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|$2208
 
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|-
 
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|Sega Logo (SEGA)
 
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|$20C0
 
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|-
 
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|Title Screen
 
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|$2288
 
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|-
 
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|Title Screen - Water Cycle
 
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|$1B66
 
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|-
 
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|Level Select
 
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|$2308
 
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|-
 
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|Sonic
 
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|$2388
 
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|-
 
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|Green Hill
 
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|$23A8
 
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|-
 
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|Green Hill - Water Cycle
 
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|$1B86
 
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|-
 
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|Labyrinth
 
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|$2408
 
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|-
 
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|Labyrinth - Sonic Underwater
 
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|$2828
 
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|-
 
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|Labyrinth - Sonic Underwater (Alt)
 
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|$2468
 
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|-
 
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|Labyrinth - Underwater
 
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|$2488
 
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|-
 
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|Labyrinth - Water Cycle
 
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|$1BA6
 
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|-
 
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|Labyrinth - Conveyor Cycle
 
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|$1BC6
 
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|-
 
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|Labyrinth - Conveyor Cycle Underwater
 
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|$1BD8
 
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|-
 
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|Marble
 
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|$24E8
 
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|-
 
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|Star Light
 
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|$2548
 
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|-
 
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|Star Light lights
 
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|$1C52
 
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|-
 
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|Spring Yard
 
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|$25A8
 
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|-
 
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|Spring Yard - Cycle 1
 
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|$1C76
 
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|-
 
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|Spring Yard - Cycle 2
 
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|$1C96
 
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|-
 
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|Scrap Brain Act 1
 
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|$2608
 
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|-
 
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|Scrap Brain Act 2/Final
 
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|$2668
 
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|-
 
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|Scrap Brain Act 3
 
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|$2748
 
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|-
 
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|Scrap Brain Act 3 - Sonic Underwater
 
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|$2848
 
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|-
 
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|Scrap Brain Act 3 - Sonic Underwater (Alt)
 
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|$27A8
 
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|-
 
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|Scrap Brain Act 3 - Underwater
 
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|$27C8
 
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|-
 
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|Scrap Brain Act 1/Act 2 - Cycle 1
 
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|$1D0A
 
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|-
 
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|Scrap Brain Act 1/Act 2 - Cycle 2
 
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|$1D1A
 
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|-
 
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|Scrap Brain Act 1/Act 2 - Cycle 3
 
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|$1D2A
 
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|-
 
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|Scrap Brain Act 1/Act 2 - Cycle 4
 
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|$1D3A
 
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|-
 
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|Scrap Brain Act 1/Act 2 - Cycle 5
 
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|$1D46
 
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|-
 
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|Scrap Brain Act 1/Act 2 - Cycle 6
 
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|$1D56
 
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|-
 
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|Scrap Brain Act 1/Act 2 - Cycle 7
 
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|$1D66
 
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|-
 
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|Scrap Brain Act 1/Act 2 - Cycle 8
 
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|$1D86
 
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|-
 
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|Scrap Brain Act 2 - Cycle 1
 
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|$1D90
 
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|-
 
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|Scrap Brain Act 2 - Cycle 2
 
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|$1DA0
 
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|-
 
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|Scrap Brain Act 3 - Water Cycle
 
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|$1BEA
 
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|-
 
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|Special Stage - Sonic
 
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|$26C8
 
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|-
 
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|Special Stage No. 1
 
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|$26E8
 
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|-
 
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|Special Stage No. 2
 
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|$2708
 
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|-
 
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|Special Stage No. 3
 
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|$2728
 
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|-
 
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|Special Stage Title Card
 
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|$2868
 
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|-
 
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|Special Stage Cycle 1
 
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|$4ACA
 
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|-
 
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|Special Stage Cycle 2
 
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|$4B12
 
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|-
 
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|Special Stage Cycle 3
 
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|$4B92
 
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|-
 
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|Continue - Sonic
 
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|$28E8
 
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|-
 
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|Continue
 
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|$2908
 
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|-
 
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|Ending - Sonic
 
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|$2928
 
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|-
 
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|Ending
 
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|$2948
 
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|}
 
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===Object Editing===
 
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====Object Pointer List====
 
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====Mappings Editing====
 
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====Object Placement====
 
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==RAM Hacking==
 
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====Main System Memory Locations====
 
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==== Sprite Status Table ====
 
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The Sprite Status Table is located at RAM address $D000. Each entry is $40 bytes long. Here is a list of all the values for one entry in the SST:
 
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{|border="1"
 
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!Offset||Size||Description
 
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|-
 
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| $00 || byte || Object type
 
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|-
 
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| $01 || byte|| Action flags. The bitfield looks like this:
 
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*Bit 0 is the horizontal mirror flag. If set, the object will be flipped on its horizontal axis.
 
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*Bit 1 is the vertical mirror flag.
 
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*Bit 2 is the coordinate system flag. If clear, the object will be positioned by absolute screen coordinates. This is used for things like the HUD and menu options. If set, the object will be positioned by the playfield coordinates, i.e. where it is in a level. Sonic uses the playfield positioning system.
 
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*Bits 3, 4, and 5 are either unused, or their purpose is unknown.
 
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*Bit 6 is Sonic's "Ride B" flag
 
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*Bit 7 is the draw object flag. It will be set if the object was onscreen when it came time to draw things. Otherwise, it is clear. There should be no reason to edit this flag, but it's good to know what it does.
 
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|-
 
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| $02 || word || Starting art block.
 
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*First nybble: Palette line the sprite will use.
 
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*Latter 3 nybbles: Starting art block in VRAM for which the object reads from. Multiply by $20 to get VRAM address; divide VRAM address by $20 to get this value.
 
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|-
 
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| $04 || long || Mappings offset
 
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|-
 
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| $08 || word ||
 
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*If in playfield positioning mode, it is the X playfield coordinate.
 
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*If in screen positioning mode, it is the X screen coordinate.
 
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|-
 
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| $0A || word ||
 
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*If the object is in playfield positioning mode, this is the X subpixel coordinate.
 
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*If in screen positioning mode, it's the Y screen coordinate.
 
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|-
 
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| $0C || word ||
 
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*If in playfield positioning mode, it is the Y playfield coordinate.
 
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*If in screen positioning mode, it is unused.
 
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|-
 
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| $0E || word ||
 
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*If the object is in playfield positioning mode, this is the Y subpixel coordinate.
 
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*If in screen positioning mode, it is unused.
 
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|-
 
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| $10 || word || Horizontal (X) velocity
 
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|-
 
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| $12 || word || Vertical (Y) velocity
 
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|-
 
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|$14 || byte ||Ground velocity (inertia).
 
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|-
 
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|$16 || byte ||Height/2
 
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|-
 
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|$17 || byte ||Width/2
 
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|-
 
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|$18 || byte ||Sprite priority (00 = front).
 
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|-
 
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|$19 || byte ||Width of the object, in pixels
 
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|-
 
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|$1A || byte ||Current animation frame to display. i.e, the frame currently being displayed on-screen, according to the animation script (currently parsed mappings frame, in other words).
 
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|-
 
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|$1B || byte ||Current frame in animation script. i.e, the frame entry IN the animation script being currently processed.
 
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|-
 
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|$1C || byte ||Animation number. When an animation ID is moved here, it's processed and displayed.
 
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|-
 
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|$1D || byte ||Restart animation flag (when $1D is not equal to $1C, animation restarts)
 
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|-
 
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|$1E || byte ||Animation frame duration (time until next frame).
 
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|-
 
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|$20 || byte ||Collision response bitfield. Tells what the object will do if hit by the character. The bitfield is in the format TTSS SSSS. TT is the type of collision - 00 is enemy, 01 increments the routine counter, 10 is harm, and 11 seems to be a special thing for the starpole. SSSSSS is the size, lifted from a lookup table in the collision response routine.
 
−
|-
 
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|$21 || byte ||Custom collision property, for special interaction with Sonic. This is used by bosses, badniks, bumpers and other objects. The way in which this byte is used is different for each object. Bosses use this byte as a hit counter.
 
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|-
 
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|$22 || byte ||Status bitfield.
 
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Counting from the least significant bit:
 
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{|border='1'
 
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!Bit||Hex||Description
 
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|-
 
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|0||$01||X Orientation. Clear is left and set is right.
 
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|-
 
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|1||$02||Y Orientation. Clear is right-side up, and set is upside-down
 
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|-
 
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|2||$04||Unknown or unused.
 
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|-
 
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|3||$08||Set if Sonic is standing on this object.
 
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|-
 
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|4||$10||Unknown or unused.
 
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|-
 
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|5||$20||Set if Sonic is pushing on this object.
 
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|-
 
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|6||$40||Unknown or unused.
 
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|-
 
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|7||$80||Unknown or unused.
 
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|} Note that these bits have different meanings for Sonic (see below).
 
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|-
 
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|$23 || byte ||Respawn index reference number, used by badniks, rings and monitors. Each destroyable object is assigned an index number (01, 02, 03 etc.) which refers to a list at $FC00 in the RAM.
 
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|-
 
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|$24 || byte ||Routine counter.
 
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|-
 
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|$25 || byte ||Second routine counter. This is used for some of the more complicated objects.
 
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|-
 
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|$26 || word ||Angle.
 
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|-
 
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|$28 || byte ||Object subtype. For example, the current monitor selected. See the Object List above for values. Has a different meaning for Sonic.
 
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|-
 
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| $29-$3F || || Object's scratch RAM
 
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|-
 
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!colspan="3" | Object-specific variables
 
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|-
 
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!Offset||Size||Description
 
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|-
 
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|$22 || byte ||'''Sonic''': Special bitfield. Counting from the least significant bit:
 
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{|border='1'
 
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!Bit||Hex||Description
 
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|-
 
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|0||$01||Orientation. Clear is left and set is right.
 
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|-
 
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|1||$02||Set if Sonic is in the air (jump counts).
 
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|-
 
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|2||$04||Set if jumping or rolling.
 
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|-
 
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|3||$08||Set if Sonic isn't on the ground but shouldn't fall. (Usually when he is on a object that should stop him falling, like a platform or a bridge.)
 
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|-
 
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|4||$10||Set if jumping after rolling.
 
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|-
 
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|5||$20||Set if pushing something.
 
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|-
 
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|6||$40||Set if underwater.
 
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|-
 
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|7||$80||Unused.
 
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|}
 
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You can add the hex values together to use multiple settings at once. Also notice that the first 3 bits (0-2) are used in the character object as a second routine counter.
 
−
|-
 
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| $28 || byte
 
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| '''Sonic''': Seconds of air left. Usually $1E; it decrements every second while the player is underwater. Beeps on $18, $13, and $0E. Countdown starts on $0B.
 
−
|-
 
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|$2B || byte
 
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|'''Sonic''': Unused
 
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|-
 
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| $30-$31 || word
 
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| '''Sonic''': Remaining invulnerability time. Starts at $0078 after Sonic is hit, and seems to decrement every frame until it reaches $0000.
 
−
|-
 
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|$32-$33 || word ||'''Sonic''': Remaining time of invincibility.
 
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|-
 
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|$34-$35 || word ||'''Sonic''': Remaining time of Speed Shoes.
 
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|-
 
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|$36 || byte ||'''Sonic''': Angle of ground at Sonic's front collision hot spot ($03 is "edge of ground")
 
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|-
 
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|$37 || byte ||'''Sonic''': Angle of ground at Sonic's rear collision hot spot
 
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|-
 
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|$39 || byte ||'''Sonic''': Unused.
 
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|-
 
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|$3A-$3B || word
 
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|'''Sonic''': Unused.
 
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|-
 
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|$3C || byte ||'''Sonic''': Set if jumping.
 
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|-
 
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|$3D || byte ||'''Sonic''': SST index of object currently being stood on. (multiply by $40 and add $D000 to get the object's address).
 
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|-
 
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!colspan="3" | Boss Variables
 
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|-
 
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!Offset||Size||Description
 
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|-
 
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| $21 || byte || Hit counter. Number of hits it takes to defeat a boss.
 
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|-
 
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| $30 || word || X position
 
−
|-
 
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| $38 || word || Y position
 
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|-
 
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| $3E || byte || Number of times to flash when hit
 
−
|}
 
 
{{SCHGuides}}
 
{{SCHGuides}}
−
[[Category:Sonic_Community_Hacking_Guide]]
+
[[Category:Sonic Community Hacking Guide]]

Latest revision as of 15:52, 24 March 2020


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SCHG: Sonic the Hedgehog

This is the Sonic Community Hacking Guide for Sonic the Hedgehog. Originally based on Nemesis and saxman's guides, this document has grown to outclass those two documents in most ways, and is now preferred over the original guides (which were written three or four years ago with limited knowledge of the game's code). This is due to the updating of those documents to give them a living, breathing nature.

Contributors

(In alphabetical order; if you are a contributor and have worked on a specific part of the guide, feel free to note that.)



References


Sonic Community Hacking Guide
General
SonED2 Manual | Subroutine Equivalency List
Game-Specific
Sonic the Hedgehog (16-bit) | Sonic the Hedgehog (8-bit) | Sonic CD (prototype 510) | Sonic CD | Sonic CD (PC) | Sonic CD (2011) | Sonic 2 (Simon Wai prototype) | Sonic 2 (16-bit) | Sonic 2 (Master System) | Sonic 3 | Sonic 3 & Knuckles | Chaotix | Sonic Jam | Sonic Jam 6 | Sonic Adventure | Sonic Adventure DX: Director's Cut | Sonic Adventure DX: PC | Sonic Adventure (2010) | Sonic Adventure 2 | Sonic Adventure 2: Battle | Sonic Adventure 2 (PC) | Sonic Heroes | Sonic Riders | Sonic the Hedgehog (2006) | Sonic & Sega All-Stars Racing | Sonic Unleashed (Xbox 360/PS3) | Sonic Colours | Sonic Generations | Sonic Forces
Technical information
Sonic Eraser | Sonic 2 (Nick Arcade prototype) | Sonic CD (prototype; 1992-12-04) | Dr. Robotnik's Mean Bean Machine | Sonic Triple Trouble | Tails Adventures | Sonic Crackers | Sonic 3D: Flickies' Island | Sonic & Knuckles Collection | Sonic R | Sonic Shuffle | Sonic Advance | Sonic Advance 3 | Sonic Battle | Shadow the Hedgehog | Sonic Rush | Sonic Classic Collection | Sonic Free Riders | Sonic Lost World
Legacy Guides
The Nemesis Hacking Guides The Esrael Hacking Guides
ROM: Sonic 1 | Sonic 2 | Sonic 2 Beta | Sonic 3

Savestate: Sonic 1 | Sonic 2 Beta/Final | Sonic 3

Sonic 1 (English / Portuguese) | Sonic 2 Beta (English / Portuguese) | Sonic 2 and Knuckles (English / Portuguese)
Move to Sega Retro
Number Systems (or scrap) | Assembly Hacking Guide | 68000 Instruction Set | 68000 ASM-to-Hex Code Reference | SMPS Music Hacking Guide | Mega Drive technical information
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