The long-timers will remember Riddler's Gauntlet. And as I'm starting to suffer from lack of mental stimulation (read "stupidity" ), I thought I'd try to revive this. So if you have any new puzzles (or want to reuse some of the older ones again ) feel free to do so
To kick this off, I'll start with a new one I thought up while at work.
I have two Coca-Cola cans side by side on my desk. One I drank half an hour ago, the other just opened. Both are identical in look and size. However, without needing to remember I and, anyone else nearby, can tell which is empty and which is half full.
Without touching or otherwise interacting with either can, how can you tell which is the empty and which is the just-opened can?
Riddlers and solvers, start your brains again