D-Pad = WASD. B/A = Left and Right Arrow Keys.
Geminid is a block falling game where you have to match symbols of the same type. Whenever the timer ticks down to zero any set of matching symbols will be scored and the board will resettle, then any new matching symbols will be scored, and so on. The later into this process symbols are matched and the greater the number of matching symbols the higher your score will be. It was originally made for GameBoy Jam (its #gbjam page is here) in rather a while less than 10 days.
The Android version of the game is a post-jam build (I didn't quite have enough time to finish it before the jam ended).