You have wisely chosen to go for a simple game idea and put a lot of polish into it for this short timeframe.
I think the randomly shuffling upgrade options between the rounds help give the game a degree of depth, making the player think about what they need to prioritize in a given moment.
Looking at the screenshots I was worried it wasn't gonna run well on my computer (i have potato computer), but it basically ran perfectly, so bonus points for optimization.
I think the game could be improved if there was more feedback for the player getting hurt. There were times where I wasn't 100% sure if an enemy hit me.
Good job!