A simple match-3. It's often said that match-3s practically write themselves, but that only applies if you can stop yourself from playtesting them repeatedly.
The controls should be self explanatory. There's a handful of different game modes too, including a "zen" mode for chilling out (or panicking if you fancy setting the difficulty a bit higher) and a Dr Mario inspired stage based mode.
You can switch the music off via the menu.
I thought that I'd have a go at making something that wouldn't seem out of place in an 80s arcade. The result was probably more like an old ZX Spectrum game, but despite its simplicity it's not the worst way to kill a few minutes.
High scores are saved between sessions.