Nice, feels great to play. Good amount of juice. Was terrifying to encounter my first interstellar death worm. Would like to see more weapon upgrades, abilities, enemy types, environments, smarter enemies, etc., but that's only because I'd like to play more of it.
There's a small flaw in your Gradius-style upgrade system I think. Once you get the other upgrades squared away, every can of Spam can restore your entire health, which feels overpowered. Maybe the upgrades should cycle, or become defunct options rather than skipped, so that HP always costs four cans of Space Spam. With the procedural generation, this game kind of reminds me of Galak-Z, did you play that?