Space Special by Jiri_One

After four failed attempts of I game I finally came up with an idea. The concept of my game is that the enemies health is dependant on your score. So you have to choose between ammo, upgrades or your score and the enemies health. (every upgrade adds 2 extra damage to your bullets). I would love feedback on it and know how to improve it.
Software used:
-Game maker Studio 1.4
-Bfxr
| HTML5 (web) | https://jiri-one.itch.io/the-space-special |
| Original URL | https://ldjam.com/events/ludum-dare/40/space-special |
Ratings
| Overall | 623th | 2.708⭐ | 26🧑⚖️ |
| Fun | 531th | 2.87⭐ | 25🧑⚖️ |
| Innovation | 584th | 2.565⭐ | 25🧑⚖️ |
| Theme | 443th | 3.196⭐ | 25🧑⚖️ |
| Graphics | 620th | 2.292⭐ | 26🧑⚖️ |
| Audio | 480th | 2.159⭐ | 24🧑⚖️ |
| Humor | 506th | 2⭐ | 17🧑⚖️ |
| Mood | 588th | 2.35⭐ | 22🧑⚖️ |
| Given | 13🗳️ | 5🗨️ |
Also it's not so clear what upgrade and buy do. A little start menu with some explanation would have helped maybe.
Maybe a way to restart the game when it is over could be nice !
The "upgrades" doesn't feel more powerful, there's very little indication of how much power you or the enemy has - the "health", if that's it, being a number on a fast-moving enemy doesn't really tell you much. I don't know how much "power" I have through upgrades.
I think improving the feedback could improve the game a lot.
And the controls are really difficult to use, the keys felt like they were all over the place.
I couldn't really figure out what my upgrades would do but i guess they're always good to have!