This one's another bog standard 2D platformer, but with a very innovative twist: The level has "fold" points, and if you drag a line between them (using the mouse) you actually define a "folding" plane. Release the mouse, and that area you defined disappears from the level! So you can shorten high platforms you couldn't reach, temporarily make some obstacles disappear (you can "unfold" any time you wish), etc.
Presentation, as with all Nitrome games, is very nice and pixel-y (none of that rendered or abstract stuff we're used to lately).
P.S. in the 2 screenshots below I demonstrate a "fold": screenshot #1 has me selecting the fold and screenshot #2 shows the playfield after the fold!