C Mods

C mods are one of three types of speed mods in StepMania, the other two being X mods and M mods.

The C stands for "constant". When playing with a C mod, the arrows will always scroll at a constant BPM of your choosing, no matter any tempo changes or stops. For example, if using the mod C400, the notes will scroll at a constant speed of 400 BPM. This speed mod is utilized by many keyboard file players.

In ITG, using a C mod on a song with BPM changes will disqualify your score for ranking. On all Novice charts in ITG, a forced speed mod of C120 is set causing the arrows to scroll at the slow speed of 120 BPM, which is helpful for novice players or those new to the game.

Using a negative C mod (like C-150) does have an interesting effect though: the arrows will come down from the top of the screen instead of from the bottom, and vice versa if reverse is on. An example of this can be found here. It is no longer supported as of SM5 for some reason.