Good puzzle fun! Messing around with mirrors and seeing the light bounce around is neat.
I did come across a bug: once you activate a color, you can remove the first mirror which the light source bounces against, and the color will still be activated, even after removing other mirrors. Seems to inconsistently happen from time to time, though - green seems a little more resistant to this.
Aside from that, amazing start screen! Awesome introduction to the game's mechanics and workings.