I've got a few more modes in the works ( classic mode (NES ), master mode (TGM3) and a few others). I don't have concrete plans after that.
I've tried a few games with pentomino modes, but I never really liked playing with them much. Though, I for sure want to have achievements in the game at some point! I had one of those brick game handhelds as a kid too :D
I also want to port the game to other platforms, once I feel like it is "complete".