Hi, congrats on your game! :) The game is really cool and has a lot of potential. I think it would be interesting to add other mechanics when entering the 'shadow mode'. Just entering the shadow mode to kill enemies seems a bit simple. Perhaps entering the shadow mode could be necessary to pass through certain areas or to activate switches, complete puzzles, and so on.
If you have some spare time, please try out my game. It's a classic space shooter from the 80s but with a personal touch. Please leave your honest feedback.