I love the interesting concept! I think that any mechanic in games that's used/dependent on a resource of some kind has the potential to be played around with and manipulated in cool ways. In your case it's the charge bar for the lighthouse. Right now the mechanic is sort of linear because it depletes at the same rate and charges at the same rate when you let go, so using the light sort of quickly settles down into a maximally optimal and sort of stale pattern of lighting up to a certain radius, letting go, and repeating the same thing. What if the resource could be manipulated by getting kills? Maybe it depletes faster, but charges back up a bit every time the player gets a kill? Maybe the shooting and the light energy is combined, making the player uses some energy when shooting, so they can't spam bullets into the dark? Maybe there are certain powerups that orbit the lighthouse instead of going straight for it, that regenerate the light bar when you shoot it? I think there's a lot of options for messing around with the charge bar to make things more interesting.
I think the mechanic is a super cool answer to the Confined theme, and I appreciate the speed and health variation in the enemy types. Congrats on the submission, and I hope you can continue working on this neat concept!