Thank you for your feedback and your advises. That your kid will like it makes me happy, because I've designed it with the aspect "how would I liked it in former days / at the 80s". Fun fact: I've designed knurps 1989 when I was a child. I draw different comic strips in a notebook of him in the past. The main story was that he's a visitor from an other planet who helps every animal who need help. In my game I've decided to orientate the design of knurps and his space ship on my drawings from my childhood. When I had known, as kid, that I designed my own knurps game when I be old, I had flipped out.
And: My children helpes me designing some of the levels. We're proud of the result :-)