Sonic Classics

Sonic Classics
Also known as: Sonic Compilation (EU), Sonic 3 in 1 (AU) Developers: Sonic Team, Sega Technical Institute, Compile Publishers: Sega (EU/US), Tec Toy (BR), HiCOM (KR) Platform: Genesis Released in US: April 24, 1997 Released in EU: August 1995 Released in KR: October 1997 Released in BR: 1997 This game has unused graphics. This game has revisional differences.

Sonic Classics is a compilation of the first Sonic game, its sequel, and Adventures of Sonic the Hedgehog-branded Puyo Puyo in one handy cartridge.

It's known for being the first compilation of Sonic games, containing every Sega Genesis game with a relation to the syndicated cartoon Adventures of Sonic the Hedgehog, and the last Sonic game released for the Sega Genesis prior to leaving the North American market (Although Sonic 3D Blast was the last "new" Sonic game released in PAL regions, and the promotional Sonic 3 movie cartridge is the last Sonic game released officially for the Sega Genesis).

Unused Shaded Font

A shaded font, possibly to make the text easier to read.

(Source: Hivebrain of Sonic Retro, Sega Retro)

Revision Differences

Region Lockout

Version 1.0	Version 1.1

Version 1.0 features regional lockout, while Version 1.1 removes this, making them region-free.

Oddities

Mean Bean Machine Sound Test

In Dr. Robotnik's Mean Bean Machine, the code to prevent the Sound Test from being displayed has been modified. The code to check the Hardware Version is still there, but the rest of the instructions have been set to no operation (with two instructions not doing anything useful). Then 0000 is moved to the RAM at 00FFFC02 (so the Sound Test will not display).

Code is activated before the SEGA Logo (Sonic Classic - USA/Europe V1.1):
  1224F6  10 39  MOVE.B  ($00A10001),D0           ; Copy Hardware Version Byte (A10001) to D0. 
  1224FC  02 00  ANDI.B  #$C0,D0                  ; Perform a logical AND on C0 and byte in D0 (basically
                                                    bits 5 to 0 will always become 0, while bit 7 [Region]
                                                    and bit 6 [Display] are kept the same).
  122500  04 00  SUBI.B  #$00,D0                  ; Subtract 0 from D0.
  122504  4E 71  NOP                              ; No operation.
  122506  4E 71  NOP                              ; No operation. 
  122508  4E 71  NOP                              ; No operation.
  12250A  4E 71  NOP                              ; No operation. 
  12250C  13 FC  MOVE.B  #$00,($00FF0A3A)         ; Move 00 to FF0A3A.
  122514  4E 75  RTS                              ; Return to start.

Code is activated before the Title Screen (Sonic Classic - USA/Europe V1.1):
  10E10C  33 FC  MOVE.W  #$0000,($00FFFC02)       ; Move 0000 to FFFC02.
  10E114  61 00  BSR     #$0BAE [10ECC4]          ; Jump to 0BAE.

Bugs

For unknown reasons (possibly due to poor compression), this compilation's versions of Sonic 1 and Sonic 2 introduces several bugs which weren't in the original games:

Sonic 1

To do: Get a visual comparison between the regular cycling palette and the corrupted one.

• Due to the different ROM addresses, it introduces a bug where Scrap Brain's palette cycling is bugged. This is due to the pointers for the palette data coming after 0x10000, while the original game's pointers being 0xFFFF. As a result, the game pulls the new palette entries from junk data.

Sonic 2

In version 1.0, the "All Chaos Emeralds" code (04, 01, 02, 06 in the Level Select) will not play the Emerald sound effect. Version 1.1 fixes this.

Grabber	Mecha Sonic

• Grabber's legs and Mecha Sonic's flame and sparks aren't properly flipped if they're facing right.

Sonic 2 (Rev. B)	Sonic Classics

• The player cannot Spin Dash off the Tornado in Sky Chase Zone. This is since the original game checking for whether the player was standing on the Tornado, while this compilation checks if they're only facing left.

Sonic 2 (Rev. B)	Sonic Classics

• The vertical conveyor belt platforms in Wing Fortress Zone do not make the player fall when they retract into the wall, causing the player to walk on air.