Pixeland is a Flash platformer where the objective is to color in all the white boxes in each level by touching them. While it sounds simple enough, the game tries to increase the difficulty by adding red small blocks that kill on contact, white blocks that quickly crumble when touched, and blocks that can materialize and trap you if you color in enough blocks, among other things. The Challenge levels then add more gimmicks like wind that messes with the player's jumps, invisible blocks and jetpacks. And the Puzzle levels round everything out with having you control multiple clones of the player that share directional pad controls and forcibly restart the level should one of them die.
Mikewilllplays here plays completes every level in the game, including all the regular levels, the Challenge levels, and the Puzzle levels, as fast as possible.