Looks pretty nice overall. I was running into the same problem as Skye, though. Couldn't spend the coins to get more laser colors, which makes it difficult to impossible to progress. It'd also be nice, at least at the very start, if spawning monsters were only of the color(s) that you can defeat. I usually end up having to run away from monsters that I can't kill. Maybe switching colors by scrolling the mouse wheel would be slightly better than the radial menu. I also didn't see any visual indication of the currently selected laser color.
Monsters seem to attack only once (which leads to a funny exploit where you become invincible if you let yourself get attacked by four monsters, after which they create an impenetrable shield around you).
One more thing that threw me off a bit is that the aiming wasn't very intuitive. I can't quite express what it is, though. It seems to always hit where the crosshair aims, but there's something about the camera angle needed to aim at a certain position that seems odd.
I think this has a lot of potential. It looks like you've put a lot of effort into building a world, and I was looking forward to a boss battle with that kraken in the background but sadly couldn't make it that far. With a bit more work I think this could be a very entertaining game.