Squares

On the surface, Squares looks like a food-chain-type game, but the difference is there is no food chain. The rules are simple:

• Absorb the black blocks (regardless of size)
  
• Avoid the red blocks (regardless of size)

Circles are special, red ones are bad, black are good. They may grant you invincibility, change the size of your square, or simply hand you a thousand points. And of course, the game gets faster (and therefore harder) as you progress.