This FAQ should be unstickied, as there is no evidence of these "guidlines".
It has to do with time, how good your time is. You can fall off and hit walls and use items as much as you want as long as you get the time required. It makes more sense than HP and duhduhduh. Let's wait until we get a good hacker to look at the code and see what values truly determine star ranks.
That's why you should use a properly calibrated CRT, not some trash LCD. MKW FC: 3351-8405-7735