Not long ago, and I came up with an idea for a little isometric puzzle game where different units move across the terrain in different manners, and the player must navigate them as obstacles. Bumping into them would have different consequences depending on the unit you run into. It's a bit like a maze, except the "walls" are always moving.
Progression through the different levels would open up a narrative about a black Rook and a white Pawn in this checker board world of sentient chess pieces.