This game is VERY impressive. It's simple, yet captivating and you've managed to make it really forgiving in lots of different ways without it feeling cheap or easy. And the steady introduction of new concepts keeps it so fresh without changing the feel of the game.
The choice to have your direction always be the same as your direction of movement is interesting, but it does mean that if your velocity approaches zero, your direction flips around unpredictably which can be annoying. But maybe that's intended.
Solid game!