Didn't get that I can draw right away. I liked how you avoided possible cheese (drawing a circle around the fish) by moving the level, nice trick. Also, the fact that the seaweed can't be erased makes you think ahead, looks like another nice game design trick.
The stars confused me though, I thought they were some kind of collectible (you know, it's a usual thing in games to collect stars, not avoid them). Maybe changing the color to a more evil-ish one or using something else would help with that.
I liked the graphics and music! Adding some sounds (for bouncing for example) could make it even better, I think.
Overall, great game!