Thanks for your suggestions! Actually, a lot of people has tell me to add a speed up button(tool), which I will do right after the game jam over. For the full screen, however, there was an issue with the zoom scale, which let me have to give up full screen.
I know third level might be too difficult and sh*t to most players since the time is too short, it's mostly because I haven't think a ideal level that can express the technics yet. As a result, I have use it since it's the best one in the level I have thought (others just being too easy or even impossible to get through).
btw, the collision check was a problem about unity, which I can almost do nothing with it (there is another player who told me the same thing and for now I'm tring to use his method to fix it)