1. There are 40 levels in Mario Kart Super Circuit. 20 new tracks and 20 retro tracks from the original Super Mario Kart.
2. There are only 40 people here because the site just recently opened up and it takes time for the competition to heat up. Also, there are other players adapting to the new track rules, so that could be another reason they haven't joined yet.
3. Well, for my videos, I simply hold a digital camera up to my GBA after a good run and use it to record a replay of said run. Some people prefer to use a Game Boy Player and record their videos from their VCR, but everyone has their own way of doing things.
4. Of course you can join. Just click the "Submit Times" link on the main page and go from there.

You may shroom across the water after the jump, but you may NOT shroom between the bricks over the water before the jump because it's going to be hard to tell whether or not you jumped over a brick in the process, which is not allowed.

To unlock the special cup you have to complete the other 4 cups in GP mode - I think on 150CC. To then get the retro cups I think you have to complete the cup a second time, but with more than 100 coins. You need to do this on 150CC to unlock them in time trials.