Thanks for the feedback!
I didn't get the chance to add sounds before Feedback Quest 6. Partly for time reasons, and partly because I hadn't added the Options menu yet, so players wouldn't be able to adjust sound volume if it was too loud. Now that version 0.0.6 added the Options menu, I can start adding sounds without much issue.
As for the gameplay, yea it's not really trying to go too far out from the SHMUP standard, outside of the leveling system that was partially inspired by Bullet Heavens (I've even been pondering on the idea of a Bullet Heaven mode). Potatostrike is partially a project where I can test new systems to implement in a bigger project later down the line. The multi-layer background and UI are some of them.