Years ago while bored on a train with a deck of cards, I made up this solitaire game (for all I know, it may already exist under another name). So I've turned it into a little Pico-8 cart, my first 'finished' game.
(as sounds common, I've started at least 4 other ideas... all in various WIP playing-around stages, it's just too much fun to try new things...)
Arrange cards to make as many good poker hands as possible. For an extra challenge, play in 'Perfectionist' mode where you only score points if you make a pair or better in all 12 hands (across, down, and diagonal), which takes some careful play and a bit of luck.
My personal best score for some time was 44, though I recently managed a 57 when the stars aligned.