Nega Kon is an Experimental Gameplay Project submission with a rather clever idea - somewhere in each level is an object that you need to fix, so that you can collect a star before proceeding to the next stage. This object appears flat at first, but pressing the X key while viewing it from a specific angle will turn the object into a solid shape. Players can then utilize this new entity to grab the prize and finish the currect level.

There are also only a handful of levels to play through, so most of us would make short work of it in just a couple of minutes. The download links for Nega Kon are available here. (Windows, 6.10MB)