Here's a test arena for some more custom monsters. There are 3 types of Zoibs, and 3 shooting patterns.
Unfortunately the scoring is currently broken for custom monsters, so you can only play for completion. When you see the sushi, you're around half way there. Tip: don't use the pickups until you really need them.
Have fun! Let me know if you can beat it.
(note: you need version 0.2.6 or later to play this level)