Thank you for the kind comment! And for being specific about what parts were confusing to you, it's very helpful to know! In case you're curious, the rule is that the piece needs to be surrounded by the specified tiles, but that the tiles "outside" the board count as the background color, which is normally light. I'm not sure if that made it any clearer. I might not be any better at explaining in text than in the game, hehe :P Anyway, thanks for giving it a shot!
The idea of a one move undo button is great by the way, it seems like an obvious addition in hindsight, but that's the way it is with good ideas :) Thanks for mentioning it