Q. How do the ratings on the site work ?
A. Well, ratings are based on number of problems solved and number of points earned. Specifically if P is the number of points and S the number of solved problems then your rating R is calculated as:
R=(sqrt(P/5000))+(S/10)
and the next lowest integer is your level as seen on the user info screen.

Q. What is the point ?
A. Well, you have to solve puzzles in order to progress through the levels. The final set of challenges will require all of the skills that you develop along the way and ultimately you will be competing against some of the best minds on the web. For those that make it to the top the mental achievement and sense of satisfaction at completing levels is all that is needed. But I won't spoil the ending for you.......