The tool modifies a single memory address that stores the FPS.
I used cheat engine to figure out the address for the FPS so if anyone has used cheat engine to properly update the game time as well given the modified FPS, just let me know how that's done.
The tool forces the game to update faster.
However, game time becomes a problem. I am not sure why.
This affects more than just playtime; if the game has anything related to a timer count-down (eg: some sort of timed event where you need to complete a task before the timer runs down to 0), you may notice that the timer runs extremely slow relatively to the speed of basically everything else. Depends how the timer is implemented of course.
So a side-effect of this forced speed up is that timed events suddenly become really easy.
However, this also means that in-game time might pass really slowly (and apparently, turns back time), so if you are hoping for time-based events to spawn faster...tool may need to be updated.
I set an arbitrary limit of 500 FPS for the tool. This was because anything faster and I noticed games might crash from time to time.
I can increase the limit (eg: 10000) or allow users to set their own limits since this affects the size of the bar if that would make it more useful, but potentially less safe. I don't actually know what causes the crash so it might not even be related to the FPS.
For perspective, RMXP by defaults runs at 40 FPS.