Not sure what you are looking for, but I think the security world has many puzzles to offer. Spot the bug in a given piece of code. Find the problem by looking

Not sure what you are looking for, but I think the security world has many puzzles to offer. Spot the bug in a given piece of code. Find the problem by looking at the patch. Switch from source to binary if that is too easy. Or look into reversing. If that gets boring, try reversing some complicated malware.