Loop pattern library
Loop (Slitherlink) is a chain of small forced deductions: certain clue arrangements always decide the same edges, no matter what the rest of the board looks like. Learn these shapes and most daily boards open themselves.
━ loop edge · ┄ forced continuation · × ruled out
The 0
A 0 touches no edges: mark all four off immediately. Every X tightens the clues beside it — zeros are pure free information.
A 0 on the border
On the border the X spreads: once the 0's four edges die, each border dot beside it has two dead edges — and a dot can never use exactly one edge, so the border edge continuing past it dies too. Six X's from one clue.
A 0 next to a 3
The classic opening. The 0 kills its four edges, so the 3 must use its remaining three. The dots between them then each carry one line and two X's — the line has exactly one way onward (dashed). Nine edges decided before any guessing.
A 3 in a corner
The corner dot uses both of its edges or neither. “Neither” would leave the 3 only two reachable edges — so both border edges are on. Free progress on any board.
A 1 in a corner
Mirror logic: both corner edges or neither. “Both” would give the 1 two edges — so both are off, and the 1's single edge lies on one of its two inner sides.
A 2 in a corner
Whichever way the corner dot resolves (both edges or neither), the count only works if the loop continues along both borders past the neighbouring dots: the two outward border edges are always on.
Two 3s side by side
Adjacent 3s force all three parallel edges between and around them, and kill the edges extending the shared one — the loop must weave, closing each 3 on opposite sides.
Two 3s diagonally
Diagonally-touching 3s each take the two edges at their OUTER corner — away from the corner they share. However the loop threads the middle, the outer corners are forced.
Follow the forced line
The engine of every long deduction: a dot on the loop uses exactly two edges. When a line reaches a dot where two of the three exits are X, the last exit (dashed) is forced. Chains of these close whole regions.
Tip · Today's hint page tells you which of these patterns is on the board — check Loop daily hints before revealing anything concrete.
Play today's Loop →