This one's pretty special. It's easily one of the best platformers I've ever played. It's fiendishly difficult in places, but it's the kind of difficulty that is very deliberate and down to great design, rather than poor controls. The controls and movement are fantastic which makes you feel like any improvement needed is yours, not the game's fault. The animations are smooth, the map is well designed and there's a great choice of upgrades and abilities. The only slight downside is the story, which just left me feeling confused for most of the game.
I have very few criticisms in general: