Very good.
It was very good, you must have spent a lot of time on this. The only problem I could find that I don't tihnk will have been mentioned is that, at some parts, it is possible to become trapped. I found this one a part where it was impossible to gain enough speed to go around a loop, unless you had made a whole line of loops and hills, progressively gaining speed. However, you couldn't go back to the start because you needed just as much speed to get back.