Good game, but with fundamental flaws
I thought the game design was very interesting, with the split functions and need for cooperation. However, it gets a little frustrating after a while, and pretty slow after the first few levels.
There are also major game design problems. The first, and mentioned in other posts, is the tendency for some of the doors to eat up more than one key at a time, meaning that it's impossible to complete a lot of the levels unless you painstakingly only pick up one key, use it, then pick up another key of the same color later on.
Second, the physics are a bit sensitive, and when trying to carefully maneuver around a pole or a wall, I often find myself ricocheting back and forth with nearly no end in sight or, worse yet, dropping off a ledge. The physics have to be improved to take into account the actual speed of the player-controlled ball.
Worth playing for about 10 minutes, but I'd stop after that.