The students above are tackling Costas arrays. The details surrounding Costas Arrays are not important. What is important is that finding a Costas array of a certain size is difficult, but that once an attempt at a solution is shown to you, it is pretty easy for you to say if it is a FAILURE or a SUCCESS.
Mathematicians call these NP problems.
When I’m designing puzzles for the elementary school math classroom I’m purposely trying to design NP problems. I expect most of the puzzles that I call Infinite Pickles are NP problems. There are pedagogic benefits (explained in “The Infinite Pickle”) for designing puzzles like this. Please continue designing puzzles like this. 😉