It sounds like you had a detailed and positive experience with the game! The art direction and gameplay pacing stood out to you, which is great to hear. Using darkness as a resource mechanic is indeed a creative touch. Your feedback about adding "juice" to your own games like this one is understandable; the atmosphere created seems both awesome and creepy.
Regarding the music, the restarting issue after passing levels might be a bug worth addressing. Your suggestion about making energy canisters regenerate health could provide a more rewarding gameplay experience, especially considering the current harsh penalty for taking damage.
Lastly, your tip from one Godot developer to another about offsetting the gun sprite to simulate holding it out is a nice touch for immersion.
Overall, it sounds like you found the game to be a successful action/horror blend with pixel art, offering a satisfying gameplay loop. Thanks for sharing your insights and suggestions!