Copy Killer by PerilousPete 2011-12-18T09:56:00
As the description says, you need to pay very close attention to the instructions. But here's a crash course:
The objective is to find the messages, you can see one in one of the screenshots above (small piece of paper). These appear randomly in levels, so even if you go to every level you might not get them all. Just go back and they will appear.
To open the doors, you need to kill all other clones in the level, then kill yourself. If you read the messages it explains why, but basically the doors open when there's only one clone left, it can't be the one you're controlling. Once the doors open, you need to get the remaining clone out the door, so before you die be sure to set it up so that this will happen. Once the clone gets out the door, he arrives in the room next door to the right or left (depending on whether you left from the right or left of the room). You then take control of this clone. Rinse and repeat.
It's a crazy idea to explain, and I had just as much trouble/fun making it, but hopefully this clears it up for you (or at least helps you past the first level :P).