A very simple improvement would be if you layered the scrolls so they register below gold- or potiondrops, thus allowing you to save the dropped scrolls 'til the end while still benefitting from gold and potions. As it is, scroll hitboxes are all over the place and seem to register at all parts of the mousepointer making it impossible to pick up other drops in the vicinity without wasting the scrolls.
Shieldships basically mean autofail unless you're very lucky. Since they automatically have a invincible shieldwall that AI's to the font of them, and then every new ship that enters the map adds to the invincibilityswarm. :/