I'm going to setup a puzzle contest for my family and friends for Christmas. The puzzles are hard, but doable in 1-2 hours (along the lines of Sudoku, Crosswords and Logic Tables puzzles).
However, I have all of them ready, except for one. I would like to propose for one of them (randomly chosen) a near-impossible to solve puzzle. By near-impossible I mean:
- It has a solution;
- The solution is very hard to find, and impossible to solve in 1-2 hours for an intelligent person with access to the Internet and a computer;
- The puzzle does not seem to be very hard (as I said before, something that appears to be solvable with some effort);
- He/She will get the prize if stating that the puzzle is impossible to solve with the time and resources given to them.
Could you help with that? I will accept the most original puzzle satisfying these constraints
in the next 24 hours. EDIT: Sorry guys, I got two answers that do not satisfy all constraints (both are far from near-impossible), so I'm going to leave the question open.
PS: Based on Ideas on puzzles for a scientific event, I came to the conclusion that this question is not off-topic (requesting puzzles).