Terminating depressed red shapes is the enjoyable task awaiting you. Yes, that is right, your goal in this game is to kill all the red shapes, whereever they may be, and put them out of their misery. They don't mind, they're depressed and do not want to go on living as a pointless shape, in a pointless world, with a pointless existence.
In a nutshell, click where you want to explode the red shapes away. It becomes a click frenzy for some levels, but it is still fun just to see these shapes die in the most terrible of ways (ie dropping off the screen into the abyss of nothingness).
If you get stuck, use the walkthrough to the right -> but if you want to show the world how merciless you are, try doing it without the help of the walkthrough.
Lots of levels, bonus levels, and challenges to keep you busy for a long time. Goodluck, happy killing.