YMMV / Understand

• That One Puzzle: 2-9's fourth rule, "the line length must be a prime number" was hard to figure out for many players. Merely figuring out what kind of rule it is is tricky because so far only two previous puzzles have cared about line length, and they ask for a single fixed number rather than allowing a group of numbers. Additionally, the pattern of prime numbers is easy to miss unless you thought of systematically trying various line lengths. It might seem as though the rule is just accepting or rejecting lines at random.