Press Space 1. Quality 2. Creativity 3. (For games) How fun it is 4. (For animations) How entertaining it is.
Sans Undertale theme. Is says three, and I now there are four, but the reason I said three is because there are only three for each project your doing (unless it's an art project, in which case the first two ones will only apply.) Also, any comments I make will always be constructive. I would never knowingly insult you. Scratch is a place of openness, not for some schmuck to say "Yur Porjet Suks" or something. Also, the rating? It's not an insult. It's so you know what to work on to make more people like it. So, if you get a low rating, don't feel bad. It means that there are things to work on. Besides, it's better to know than not know.