Welcome!

This hacking guide is meant to be an information storage about the game's internal workings. It was started back in early 1999, when Sonic hacking was just getting 'popular'. Seeing how hacking geniuses uncovered the workings of MegaDrive / Genesis games, I started a two of them myself, covering less-mainstream Sonic games. One perished shortly due to emulation issues, while the other one not only survived, but it became one of the leading Sonic hacking guides in the 'net as well. The amount of uncovered info in Sonic CD is simply remarkable, and I must say that what you see here are simply basics. This small page has a long way to go before it will cover at least 90% of Sonic CD's internals, but, needeless to say, the staff will do their best to achieve that goal. ^_^

Before you came here, you've probably taken a look at some of Saxman's Sonic hacking guides. Well, this, at the end, isn't all that different, but the basics are very easy to start with...you don't even need a hexeditor to perform some of these hacks.

Before I go on any further, let me tell you what you need:
- a copy of PC Sonic CD, fully installed on your hard drive
- a good file handling program (DOS prompt will do, but you never know...)
for the absolute basics
- a hexeditor (required for almost everything below)
- a RAW graphics viewer (you can download one off the page)
to do the graphics
- a copy of USA/European Sonic the hedgehog MegaDrive ROM
to do some intergame porting
- a RAW sound/music player
...for messing around with the game's sound.

You start by replacing Sonic CD's files. To do replacing, SCD must be fully installed on your hard drive (make sure your game loads data from the HD, not the CD unit). It can be done in any program with file replacing/switching capabilities, like Windows Explorer (eeeww).

To learn about files, visit the files section of the page.

Further techniques require the use of a hexeditor; the section utilising it is mostly about graphics; it can be used for altering everything in the game though.

See graphics section for details.