Pretty solid visuals for your first game! I like space games so I wish it has sounds to make it more enjoyable. I actually didn't manage to get upgrades, I thought it was a weird choice for the game to start you at 0 damage, instead of just 1. So I was just flying around for 90 seconds, and I didn't quite know what to do haha.
A full-fledged built-in tutorial could be nice but if it's too close to the deadline I think you could just resort to write out the tutorials and what the players need to know to play the game in the description of your project page (which is what i did).
Either way, good job on finishing and submit, but I reckon there's still a lot left to do on this game, so I hope you would continue to improve on it some more!