Difficulty ratings, explained

Every 8flowy board wears a tier — easy, medium, hard or expert — and a 1–100 score. The label isn't a guess or a designer's mood: it's measured from the finished board, after generation, by walking its unique solution and counting the ways a careful human could go wrong.

What actually makes a flow board hard

Not size, mostly. A 10×10 with twenty short pipes is long but easy — every pipe is guided by nearby dots. What makes a board hard is plausible wrong turns: moments where a legal alternative route looks just as sensible as the correct one and nothing on the board visibly refutes it. You commit, draw three more pipes, and only then discover a stranded square.

Three visible features drive that count:

Fewer pairs. Fewer dots means longer pipes with longer unguided stretches, which is where wrong turns breed. This is the main difficulty lever.
Longer single pipes. The longest pipe on the board is usually where the puzzle's whole tension lives — a pipe that must wander to soak up empty area.
Board size. Bigger boards multiply everything and stretch your working memory.

The score

After a board is generated we walk its unique solution pipe by pipe. At each step we count the alternative moves that are legal and survive the quick checks a careful player runs in their head: can this color still reach its other dot? Is any empty region cut off? Is any empty square left with only one open side? Every surviving alternative beyond the true move is one chance to go wrong. That count, blended with pipe sparsity and the longest pipe, and normalized against a per-size baseline, gives the 1–100 score:

Easy (1–27): the dots crowd the board; most moves are forced.
Medium (28–49): real choices appear between the dots, but each is refutable a step or two ahead.
Hard (50–71): long unguided stretches with routes that die only much later.
Expert (72–100): minimal dots, wide-open area; plan the whole network before you draw.

The score is relative to the board's size — it answers "is this a hard one for its size." A sparse 5×5 can grade hard, and a dense 10×10 can grade easy.

What difficulty never changes

Every tier keeps the same guarantees: exactly one solution, discoverable by reasoning alone. A harder rating means fewer signposts, never a fuzzier answer. Tap the difficulty pill above any board to see that board's own numbers — its wrong-turn count, longest pipe, and score.

Curious how the boards are built and verified? See how the puzzles are made.