From Sonic Retro
|Publisher(s) of original games: Sega|
| Developer(s) of original games: |
Sonic Team, Sega Technical Institute, Compile
|Game total: 3|
|System(s): Sega Mega Drive|
|Original system(s): Sega Mega Drive|
|ROM size: 3 MB|
|Number of players: 1-2|
Sonic Classics, known as Sonic Compilation in Europe, is a compilation of three games for the Sega Mega Drive stored on a single cartridge: Sonic the Hedgehog, Sonic the Hedgehog 2, and Dr. Robotnik's Mean Bean Machine. Sonic Classics was included as a pack-in title with some editions of the Mega Drive hardware in Europe. The game was not released in Japan.
The three games appear in almost exactly the same form as in their original release, with the exception of some revisions to their code (see their individual sections below). The only new content is a game selection menu, controlled by using the and directions on the D-pad and new sprite renderings of the box art for each of the three games. Once a game is selected, players are not able to go back to the menu unless the console is reset or turned off and on again.
This game is one of two that, when "locked on" with Sonic & Knuckles, will enable players to play the entire Blue Sphere game, instead of just one level. The other game that enables this is the standalone version of Sonic the Hedgehog. This is because when locked-on to a ROM larger than 2MB, Sonic & Knuckles maps the last 2MB of the locked-on ROM rather than the first 2MB, and Sonic Classics happens (or was designed?) to put Sonic the Hedgehog at the 2MB mark. This is a quirk in the Sonic & Knuckles cartridge's mapper, which is not reproduced in emulators.
The background music and chime heard when a game is selected in the menu are from Dr. Robotnik's Mean Bean Machine itself.
Sonic the Hedgehog
This version of the original game is the same as the standard worldwide REV00 release, except for a new bug in Scrap Brain Zone involving the cycling palette. The bug is caused by the fact that the pointers for palette data are only two bytes long. In Sonic 1 alone, this isn't a problem because palette data lies within the first 0xFFFF of the ROM. However, in Sonic Classics, the data comes after 0x10000, so part of the address is truncated in the pointer, causing incorrect data to be loaded.
Sonic the Hedgehog 2
It was conjectured for some time that the version of Sonic 2 included in Sonic Classics was the former game's REV02, i.e. a second update to its code that had been officially (if silently) made by Sega themselves. This was shown conclusively in June of 2012 when Esrael, who was now using this version as the code-base for his famed hack Sonic 2 Delta, released a ROM of the game extracted to work on its own and followed this shortly thereafter with his disassembly of said ROM, which demonstrated that Sega had implemented various bug-fixes and other alterations to the code in time for Sonic Classics.
There are several issues with the version of Sonic 2 included in this compilation. Contrary to popular belief, these bugs are specific to Sonic Classics, and are not present in any other known instance of REV02 (Sonic 2 for Mega Play, Knuckles in Sonic 2, Sonic Jam).
These bugs are seemingly caused by corrupted constants in the game's source code, with all of them relating to nonsensical bitmasks.
- The sparks that Mecha Sonic leaves when he slides are erroneously not mirrored when he turns around.
- The above issue also affects Grabber's legs.
- Sonic/Tails is no longer able to Spin Dash off the Tornado in Sky Chase Zone, and instead briefly hovers in the air.
- In Wing Fortress Zone, the vertical conveyor belt platforms no longer cause Sonic/Tails to fall when they retract into the wall while they're stood on it. This causes them to be able to walk on the air.
The original cheat codes contained on the cartridge still work here, but the game enhancer codes do not.
|Main article: Sonic Classics/Hidden content|
|Main article: Sonic Classics/Manuals|
|Mega Drive, NZ|
ROM dump status
|Sonic games for the following systems|
|| 1991 Sonic the Hedgehog | Sonic Eraser 1992 Sonic the Hedgehog 2 1993 Sonic the Hedgehog CD | Dr. Robotnik's Mean Bean Machine | Sonic Spinball 1994 Sonic the Hedgehog 3 | Sonic & Knuckles 1995 Chaotix | Sonic Classics 1996 Sonic 3D: Flickies' Island |
Prototypes Sonic 2 | Sonic CD | Sonic Spinball | Dr. Robotnik's Mean Bean Machine | Sonic 3 | Sonic & Knuckles | Knuckles in Sonic 2 | Chaotix | Sonic 3D