the rocks should definetly be spawned in at the begining of the game, and the walk speed is very slow, could do with sprint and jump too. the begining of the game is feels realy slow, you should definetly start with less rest time, and/or cheaper upgrades. music and art are pretty cool though! also a way to exit the game without alt F4 would be nice, aswell as other settings(sound volume, but also the possibility of removing the post process effect as it may make some players dizy) also a very important thing: feel and feedback! if a player does something, anything, there should be as much (but not too much) feedback that they did something, that can be sound effects, particles etc. if you added particles to when you hit the rock, and a big particles explosion when you destroy the rock (maybe even a couple of rock debris fragments flying around) it would make the game feel a lot better, and engage the player more
even after i got all of the upgrades i couldnt be bothered to get enough points to launch the ship, because it just took too long.