First game I am giving 5 stars all around! There were a lot of things I really liked about this. The weapon variety was fun and I really liked the modifier system making you consider where to place each weapon. I was going to say that it'd be cool to be able to rearrange the weapons on the planet but once I got to the point I had all the upgrades I had plenty of cash to just rebuy things and experiment. I also really liked the story and specifically that you incorporated the spinning into it with the sunlight requirement for PETAL (also I'm a huge sucker for a good acronym and you had a few!). The enemy variety was also quite nice!
As for my constructive feedback, I think either the planet is too big or the plat area is too small. I felt very cramped the whole time even without trying to dodge the enemies and a lot of times they'd be in my weapons because the weapons were so big.
The "lore" text was a little small and that made it kinda hard to read on the background. I think this could be fixed with either shadows under the text or just bigger text as it was a lot easier to read on the buy menu.
Finally, I reached max level wayyy before the gg screen which was nice in that it let me experiment with the weapons, but I feel like the back half of the game kinda lost that sense of number go up that is really satisfying about bullet heavens.
Overall, great stuff!