There are a lot of tower defense games out there, and this is one of them. I guess I must like these games a whole bunch, because I played this one for quite a while, even though it's a lot like other tower defense games. The gimmick with this one is that the creeps don't actually go away, they just march around and around until you kill them -- very considerate, really -- and if more than 100 accrue, game over.
Flash Circle TD [Candystand]