This was interesting to play. Pretty simple, easily understandable and easy to get into which is perfect for a jam game. Really well done :)
The music sounded good and definitely added a sense of ramping tension, but please add an option to turn it off and/or down.
I almost felt like everything was a bit small on the screen, like you are looking at the enemies but it's hard to tell when you are to line it up and there's a massive expanse of empty space. Perhaps making the sprite a bit bigger would help?
I feel it would also benefit from a sustained noise when energy drains or the space bar is held as a couple of times I head it down thinking it was easiest and didn't realise my bar was draining. This is compounded by the fact that everything is so far away you are looking at one size of the screen or the other and don't really get the bar in your peripheral.
It also seems that your exit does nothing and your restart button acts as an exit button.