Pixel Field, a maddening yet highly addictive Flash game. Feels like trying to cram a baby into a barrel full of eels, or something. Angry eels, and a difficult baby. Maybe with Jell-o involved.
Maybe not like that exactly, but you know, odd.

Part of Tile Based Games, a guide of sorts to creating exactly that using Flash5, presented in something very close to English by the helpful Tonypa.

Pixel Field @ [tile based games]