Cool idea that fits the theme well. I did a few rounds and the best score I got was 55. I like the concept of having to find and shoot enemies that are obscured by darkness.
I feel like the game might benefit by having ways for the player to locate enemies more easily. I found myself losing track of enemies and spending more time trying to clear out the multiple enemies right next to me instead of trying to find them in the dark. Maybe you could make your light bigger by holding a button, but it drains the charge or something so you can't overly rely on it. Something like that could give the player more decisions to tackle situations like that without trivializing the challenge in the process.
Besides that, I think this is a cool concept. With some more mechanics to help balance out the difficulty, I think this could be a really solid arcade-style game. Nice job!
EDIT: Even though I read the description, I somehow glossed over the fact you can press Tab to bring up the menu to buy turrets. After that, I was able to get a much higher score of 289. I still think the game could benefit from giving the player more decisions to make like I mentioned earlier. The turrets helped for sure, but I found myself still spending more time dealing with nearby enemies rather than engaging with the game's main mechanic (searching the darkness). With that said, I enjoyed the game enough to give it a few tries and would like to see this concept expanded on.