It was obvious after I'd made the first guess, but it wasn't obvious up front that the 80 second timer was for 3 guesses, rather than 1 - I think that was what tripped me up. I thought I had 80 seconds to come up with the best single guess I could think of. It was clear after guessing once, though - maybe a skippable 1-question "tutorial" for first time visitors?
As an additional thought, it'd maybe be neat if, after making your 3 guesses, you got 1 chance to guess the actual correct answer for some kind of bonus. It's possible that that would be confusing, though (switching from guessing 'wrong' to guessing 'right' and back again).