Shift your color to absorb like-colored bullets and boss hearts.
If you are the same color as a BEAM you can pass through it safely.
Controls by default:
-ASWD = movement
-UP ARROW = white
-DOWN ARROW = green
-RIGHT ARROW = blue
-LEFT ARROW = red
Quality and music can be toggled in the R-click menu
4 difficulty settings, 5 bosses.
Good luck!