That would have been easy, as would have trapdoors been.
My plan is to have an extended piston holding back lava, when you press the wrong button, it retracts. The hard part was getting it to retract for long enough to allow lava through.
The insanely difficult next bit is to have it on multiple levels, where the right answer releases water instead of lava, and you can swim up through the water to reach the next level. I don't think that's feasible though unfortunately, it's going to be hard enough for one level!
Having said all that, some preople really do have too much time on their hands, but make awesome redstone stuff - see this piston-engined train for example:
http://www.youtube.com/watch?v=IzzxS_MP8sQ
Well, the first 'draft' of it is at the top of my tower
Images:
It's sort of finished now - as it's at the top of the tower, I don't have that much room.
Give it a try, just have some water handy!
I can't remember if I left the lights on or not though, so you'll have to hunt around for the switches if you can't find your way to the top...
Also, anyone know of a decent guide to making Rail junctions?
So I don't need to ask Kev every time!
Thanks - the floors are just experiments with light - there's no danger, other than getting lost when it gets absolutely pitch black.
The only danger is getting caught by the lava at the top, but I'm not cruel enough to make it a genuine death-trap (which would be easy to do, extend the timer by a short amount, and make the wooden door an iron one).
If you want though, pretend the door is an iron one, press the button, and don't move - you'll get the same effect!