For some reason I don't like filling sounds and the sounds of splitter (line) attaching to a surface.
Combo sound sounds like mono. On the ambient sound background it sounds really bad.
Still, you can shoot sitting inside an enemy.
I think killing all enemies on the screen should autofill entire surface.
Starting world selection is much better.
Starting level selection is buggy. You can drag and drop this guy to a further distance than moving him using left/right arrow.
Writing 99% when level is complete is confusing. How about cool INFINITY sign there instead of two digits?
(more to follow)