Slitherlink

Draw one closed loop along the edges between dots. A number is the exact count of lines around that cell. A blank cell has no count to meet.

The loop cannot cross or branch. Every dot touched by a line must have exactly two lines. Separate loops do not count, even when every number matches.

Tap a cell, then Top, Right, Bottom or Left to change a side. Choose Line to draw, Cross to note an unused edge, or Erase to clear either. Repeating Line or Cross on the same side clears it. Crosses are notes; unused edges can stay blank.

Keyboard: Tab to the cells or edges. Arrow keys move between cells, or between parallel edges. V switches edge orientation. Enter or Space acts. L, C and E choose Line, Cross and Erase; Delete clears a focused edge. H requests a hint. Ctrl/Cmd+Z undoes; Ctrl/Cmd+Shift+Z or Ctrl/Cmd+Y redoes.

Your current board and solved/seen IDs save in this browser when storage is available. Undo/redo lasts for this session. The original bank contains 12 boards at each size. Sizes are not difficulty grades; there is no account or device sync.

Rules: Nikoli.

A 0 excludes every side of its cell. A clue that already has enough lines excludes its other sides. At each dot, a path must continue with one other line; it cannot branch or stop.

Hint checks your current lines and crosses and explains a forced edge. Apply hint makes that move separately. If your choices conflict, undo or erase a line or cross. A bounded check can stop without finding a deduction.

Reveal replaces the whole board with its complete answer and marks the puzzle as assisted. It is separate from Hint.