Gareth: I might be an idiot, but isn't the information on whether your answers are right or wrong withheld from you until the test is over? That means you can't just submit one answer, see whether it's right or not, and then try another answer, because the only way to determine that your answer is wrong before the opportunity to change your answer disappears, is to solve the puzzle.

Yes, currently. I was talking about the possible change discussed above (motris's post 4744) whereby you are told immediately if your answer is wrong and are given a chance to resubmit for less points.