What does the The Mesh puzzle teach?
Cover every region with the fewest edge PoPs — minimum set cover. Greedy 'most-coverage-first' is a strong heuristic but not always optimal.
Why do interviews ask about this?
Minimum set cover is the coverage / placement interview (CDN PoPs, monitoring) — and a canonical case where greedy is only an approximation.
How is it scored?
The engine computes the provably-optimal answer for the exact instance you played (dynamic programming, shortest-path, or exhaustive search — never a heuristic) and scores your attempt as a percentage of it. No login needed to see your score.