I’m not sure, level 6 maybe? I’ve encountered the exploding sphere things, are there any enemies beyond that? I might replay and see if there’s more.
I think different wall textures and some decoration objects would already add a lot of variation to the levels. And maybe some windows to make levels feel a bit less isolated. The game takes place in space, right?
I’ve noticed an earlier version of this game that was created for the Linux Game Jam 2019. It’s so awesome! I develop all my games on Linux too. I’m hoping to participate in the next LGJ. :-)