When I died I was still able to control and play the game as normal if I ignored the game over menu. Even managed to get an upgrade lol.
The HUD disappeared for me after a few rounds. I'm not sure what triggered it.
Is it possible to exit the game? I couldn't figure out how so I had alt-tabbed out. Definitely want to implement that asap for a game that's supposed to be played in fullscreen.
There were significant shader stutters when no effects spawned when I first started playing so you definitely want to look into mitigating that somehow. A godot classic.
Some suggestions:
Have the heart hud have a recovery animation (i.e. its red color slowly climbing back up before can use) so players have a feel for how long they have to wait to dash again.
More dynamic splat effects and hit sparks. This is a type of genre that lives and dies on juice. I like the damage indicators you already have. The dash effect could also be a little more interesting I think.
Anyways it's very early but I like these type of simple action games so I'm looking forward to how this progresses. I like your cover art.