I think your game lacks a bit of content. First of all, I already died twice because no enemy got in sight before my energy was gone. Then, the graphics aren't really good. The core mechanic works, even if I think allowing us to aim with the mouse would have been better.
So yeah, maybe try to rework it cause the core mechanic is fine, but it needs polishing ;)
Yeah, it's the numbers that are all *borked* here:
* Energy runs out so fast that enemies don't even have time to close in, if you stand still * Enemies spawn in huge hordes. Trying to collect a battery is super risky due to this * Enemies take loads of hits, meaning the little energy you have left might not even last against a single enemy
If the numbers were ok, this would be a very basic shooter. At that point you could start adding in new enemy types, weapons, powerups, the usual stuff.
The HUD issue is probably related to UI anchors. They are critical for having a scalable GUI.
So yeah, maybe try to rework it cause the core mechanic is fine, but it needs polishing ;)