Couldn't rate it lower than 5/5. Translating kinetic movement into light physics results in a very original mechanic. Besides, not cluttering it with thousands of shaders gives it a 2000s vibe that I personally love (nostalgia wins).
Regarding gameplay, the game goes straight to the point, with automated move, so the player just has to care about aiming; pure darts game with a twits. It's arcade feel is amusing enough to empty your mind for a while. This is the kind of game I would like Windows or GNU/Linux distros to have preinstalled, so every now in a while you can get away from tasks han have some little, uncompromised fun.
The cowboy music makes it even funnier.