Patterns were fun at the beginning, I enjoyed the puzzle-like nature of the levels, though they started getting pretty hard. Then I started using dash and I realized its absolutely broken and you can just mash space and pretty much not get hit at all due to iframes (I think the black bullets are an exception to this). Besides from that, I think the dash doesn't serve any integral purpose for the gameplay other than being a safety measure/difficulty reducer, so if you were to balance the levels I'd say you'd rather just remove the dash altogether. You can see how that other game in the jam, Tower of Bullets, uses dash as pretty much the central thing in the whole game, but here it's just there because the game is hard and it's helpful to overcome the difficulty (or in its current state, completely trivialize it if you spam it).
Some music and SFX would've been good too, even royalty-free music is fine, as long as it matches the game. SFX for turrets shooting (not overdone or else it will be a cacophony) and for the player's dash would work well too.
Also I think the door on the last level doesn't do anything, but you probably already knew that.