At first I didn't figure out how to upgrade the ship, I got like 300 upgrade points with the base ship ^^'
Once I understood how to open the shop the game was really engaging, it reminds me of Captain Forever Remix.
I would suggest to put the shop menu in the pause screen (so esc opens the shop and also pauses the game?) or to put a big popup explaining how the shop works the first time you get enough upgrade points to expand your ship.