Very cool concept, and the designs are very interesting! Would be better if the Japanese was actually correct though. On level 16, there's a sign where it looks like you tried to write スピーディ (speedy), but it's written wrong.  Since it's vertical, the dash in the middle should be turned 90 degrees. Additionally, you put a circle next to the テ when it should be two lines, sorta like a quotation mark. I can't even type it with a circle because that's not a letter!  Always double check your work :)