Great game !
EDIT : (my mistake here)
But, please, don't forget that some players don't use a qwerty keyboard : for me, it was terrible to use such keayboard configuration (imagine the situation transposed to qwerty: "z" for up, "q" for left, but still "d" for right and "s" for down). If you can, propose a custom configuration, or at least an arrows possibilty).
By the way, your game is as beautiful as hard to play ^^ Well done !