Probably one of my favorite entries so far based solely on how much I enjoyed it. But, I do particularly like these sort of platformers.
The main mechanic is clever and very well implemented. The level design makes good use of it.
The lines between pixels and the screen transitions are very nice touches and make it feel like a real Nokia game.
My only critique is that visually some of the elements are confusing at times, just because they're so simple. The player doesn't look very distinct, and at one point it was difficult to tell which way the spikes were facing. Overall, though, it was never a big deal and didn't really affect my enjoyment of the game.
Great job, keep it up!