Chesskid is a great site for kids.
The Christmas Puzzle, Part One.

oh here is the solution guys lol, took ME FOREVER TO FIGURE THIS OUT
no, you have to start with 1.e4
oh here is the solution guys lol, took ME FOREVER TO FIGURE THIS OUT
no, you have to start with 1.e4
This puzzle has defeated Kasparov, Karpov and Botvinnik.
...and their students at the Botvinnik Chess School too! This puzzle was dubbed as the most difficult problem.