Thanks for playing! I'm glad you enjoyed the game!
You're right - the core gameplay is rather simple, so I had quite a few more features planned for the game originally to combat that - for example one that'd allow the player to teleport to a pre-spawned nearby turret if you kill enough enemies, which would make you survive a bit longer. But towards the end I ran out of both time and energy so I had to hustle to get the game out before the deadline haha. (I made the title screen, game over screen, cover art, looked up sound & music, exported the game, set up itch.io page, uploaded the game to itch.io in 2 hours. Wasn't fun. Not recommend.)
I'm happy to see that you enjoy the health/energy system. I orignially only intended to include health, but then that'd make the player too powerful (full bullet punchthrough) or too weak (no punchthrough) so some restraint must be in place. I tried to increase the reload time between shots, but that makes the game unbearably unresponsive, and, well, there's not much time to add anything complex. So I made the energy bar instead - which I find kinda boring considering a heck ton of games already use that, but it works.
Thank you for your detailed feedback!