I took your exam and got 8/10. Looks very nice. The only thing I'd think about doing... is not closing the browser window when I click the 'end exam' button. It was quite surprising, I think in general users would expect to be taken back to the start screen, if they want to take a new exam.
However, if your business requirement is to close the browser, then bravo, you've done it.
The second time through, it allowed me to login with the same number, but a different name. Maybe this is ok, but thought I'd say something.