We'll openly admit it, riddles aren't our strong suit. We like Sudoku.

No, wait, what's that one we always get mixed up with Sudoku? Jenga! Yes, we're good at Jenga!

Anyway, TedEd have put together a riddle about zombies, scientists and a bridge, and despite sounding like the lead-in to a really crappy joke, it stumped us for far longer than we consider acceptable, even by our standards. 

Have a go yourself, but be warned, the answer is unveiled at the two minute mark, so be ready to hit pause if you don't want to ruin the fun*.

*Endless amounts of mental torture.