I dreamed this one up this morning as I was waking up. So, you have a bunch of tetris pieces including the one square, the two square, and the two three squares. You have a 2d vertical grid, like bejeweled, but with fewer colours so there are reasonably large contiguous areas. Then on your turn you have to use as many of your tetris pieces as possible onto one of the colours on the grid. When you're done, those pieces disappear, the rest fall down, and the remaining space is filled with random pieces.

It's the kind of thing I'd code up first to see if that basic loop is engaging before properly gamifying it (putting a timer on, or eliminating pieces if they don't get used within a time limit, or even just making it a more pure puzzle to be solved with no refilling of the grid). But it seems like fun!