From Sonic Retro

Sonic Retro emblem.svg The main article for this category is Sonic hacks...
Knuckles the Echidna in Sonic the Hedgehog is a hack that allows a player to play as Knuckles the Echidna in Sonic the Hedgehog, a feature that Sega intended to be possible using Lock-On Technology, but ultimately removed due to technical problems.

Sonic hacks are altered versions of Sonic the Hedgehog games that have been edited through the process of ROM Hacking. From the emergence of Cyan Helkaraxe's Sonic 1 Beta Hoax in 1999, the production of hacks has been a vital part of the Sonic research community and scene. Starting with the early documents penned by Cyan and saxman, to the Nemesis guides, the Sonic Community Hacking Guide, and beyond, researchers have used their understanding of the Sonic games to alter them in various ways. While earlier hacks were simple, such as minor palette changes, a number of hacks today are very complex. Over time, as the scene learns more about the underlying code behind the ''Sonic the Hedgehog series, the extent of these modifications has expanded. Modifications now include:

  • palette changes
  • sprite changes
  • major art (title screen, HUD, et al.) changes
  • level art changes and original level layouts
  • music and sound changes
  • importation of levels from other games
  • changes in movement engines or bosses
  • original concepts and gameplay styles

Today, with the assistance of hex editors, disassemblies and specific Sonic Hacking Utilities, fans have been creating more extensive modifications.

Hacks in the Sonic community are now usually distributed as full ROMs. In the past, IPS patches were used, since these are usually much smaller than a full ROM and were, therefore, easier to distribute in a time when dial-up was widely used. It was also believed, that since patches do not contain any copyrighted code, it was not illegal to distribute one. This format fell out of use when split disassemblies became available as a way to edit game data, and when dial-up was being replaced by faster broadband connections. The massive shifts in the ROM that can result from reassembly made IPS patches very large, and they would often contain a good volume of code anyway, thus eliminating the alleged legal advantage. Though saxman's RXL patch format was designed to replace IPS, it quickly faded into obscurity along with its predecessor. Another format, [1], takes shifted data into account, resulting in much smaller patches. (Note that xdelta-1.x used the original format known as xdelta; xdelta-3.x uses the standard VCDIFF format.)