A very basic competitive puzzle game I made in about a month when I was in high school. Players build up a wall from falling blocks and then try to demolish their opponents' walls.
The graphics are very basic, but convey some useful info. For instance, lighter bricks break easily while darker ones are more durable.
While building, the game has a slower, methodical pace — but when things start blowing up it's a free-for-all. I like how the player's attention basically switches to his or her opponent's side of the screen when on the offensive.