Got up to level 4, I think? There is a turtle in the corner that I just could not hit for damage ever. Not sure how'd you feel about adding preview lines to the already shot heroes if you bounce them.
On the same level, the Healer ended up flying off the map. Could not tell you how it happened.
That said, I've played a lot of these breakout games on mobile and I like that this one is actually attempting to be a real game with actual gameplay.