First of all, thank you very much for your constructive feedback! It's really nice to hear!
I'm glad you enjoyed the game overall.
Bats cannot be killed, but they can be temporarily neutralized using light when they approach us.
Light has multiple uses, such as spotting barrels/chests, crossing certain passages, and neutralizing enemies. However, we are aware that this is not enough, but unfortunately, we didn't have enough time to implement all of our ideas.
You're right about the upgrades, they take a bit too long to obtain. We should make them more accessible. Our goal is to encourage players to descend to lower floors for better rewards and faster upgrades, but we'll need to reconsider level generation to motivate players to go further down.
Lastly, you're absolutely right, there are some missing instructions to help the player better understand what to do and how to play!