Great Resource!
Considering that there are something like 8192 key combinations, not every one of those combinations is possible, useful or desirable! The fingerings displayed for a chosen note are ranked as normal, replacement, and extra, with the “impossible, useless, and undesirable” fingerings left out. (Those are combinations where the same finger has to play two or more keys at the same time, or combinations where keys cancel each other out or have no effect.)
A nice feature is the display where you can try out your own combinations to see the result. (You can even take a look at those fingerings that were deemed not playable!)
The setting to reverse the key colors is a nice touch too!