Generally a good game. One question though, about the behavior of the cube: why lots of times the cube keeps moving despite I am not pressing one directional key at all or I am already pressing another one?
Seeing NeonSpider's review I came up with this theory: for me the game worked quite well, maybe only a bit slow sometimes, but not to the point of a massive lag. Every level is playable. But indeed the game is slowing down at some points and it may happen that it is reading the keyboard input with a delay-or rather the results of the keys pressed are displayed with a delay, so the cube is moving not because of the key you are currently pressing but because of the key you were pressing parts of a second earlier. This made some levels a bit more difficult, because you actually had to predict the movement of the cube.