Bloons
Bloons are what Monkeys call Balloons - they're daft aren't they - but they did beat humans into space, though Cats got there first. There is only one aim of the game and that is to shoot Bloons, isn't it nice when things are that simple? Oh by the way there are 50 levels and they do get a bit harder as you progress. Tip: Hold down the mouse button and let go to shoot further.