It  looks nice, good job :)

I think you should change a little how the character is controlled. You should use some maximum mouse distance and beyond it do not increase the speed. Now the player can move really fast, but only in few directions on the few places. (sorry for my english)
And also consider adding sound for picking up the key.

the music is a bit strident and the character seems to move a bit slowly, it's quite hard to dodge enemies! But overall nice concept, good job!