Many years ago, I programmed this game in AS3 and released it on Kongregate. Now I rewrote in for Pico-8.
Game play: join exactly 4 blocks of the same color to make them disappear. If you connect more than 4 blocks, they turn grey and cannot be removed any more.
The game will display a summary of your run at the end, and keeps track of the 5 best scores.