Just a suggestion for additional user interaction:
Add two mobs; a friendly Goobert and a non-hostile Gooblin.

The Gooblin is a non-hostile (until hit) mob that randomly drops Goo blocks. They are cowardly creatures that will run away if approached.
The Goobert hops around, taking care of any goo outbreaks if provided resources (i.e. Goonades.). Goobert's movement is random and he is not very fast but could be effective to help protect an area from Gooblins.