The power-ups look very similar to each other so its hard to tell what I'm getting when I'm focusing on an enemy. What I'd suggest is a small popup when collecting a powerup.
The hud on the right is confusing when you're jumping in for the first time so labeling them would be nice. Ammo, Energy, Missiles.
Holding shift to sprint when not moving costs stamina. I feel like stamina should only be drained when moving IMO.
Avoiding enemies is easy if you're wrapping around the screen, which is great if you're out of ammo and want to get to the next wave, but if you're unlucky, the next wave will hit, you'll still be out of ammo and the enemies will just keep spawning. Eventually the whole screen will be filled with enemies. Gaining ammo on a new wave or enemies from the previous wave being deleted would be great. I've also noticed some collision problems when too many enemies are present.
Pressing escape to exit controls menu when the game is paused brings the pause menu back again but doesn't close the controls menu.
Pressing escape in the settings menu doesn't take me back to the pause menu.
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I really did enjoy the game so far though, and I can't wait to see more :)