Hey! Thanks for trying and leaving feedback! It could be that my instructions are not clear enough, but usually players get stuck when they cross out the prime factors before a square of a prime. For example, if you have 25, 5, 5, and 1, etc... on the board, canceling the 5s first leaves you stuck with 25. Since 25 only has prime factors (5 and 5) besides 1 and itself, it requires that there be other multiples of 5 on the board; otherwise, it will be unsolvable in that state. Anyway, thanks for giving it a try!