The purple stars are scary. They really make me appreciate my shot's humongous hitbox. As do the rockets, since you can nuzzle up next to them from above or below and take them out.
I'm still scraping by on my last life through this stage--those sperm enemies at the end really get me. You just can't hang out near any edge of the screen during this stage, and when I lag to clear out the sperm guys, I'm really pressed for space.
At least I memorized that trap with the final pair of rockets.
I also just successfully won a beam duel against the boss. It gets pretty harrowing, since even if you have full beam, he'll go on to continue his pattern partway through (while you continue to beam him). If you can keep collecting newalone and refreshing your beam, though, he should go down shortly.