How to play

Draw one closed loop along the grid lines. Every number says how many of its four sides the loop uses.

• A 3 has the loop along three of its four sides. A 0 has the loop nowhere near it. Empty cells say nothing — the loop may do as it likes around them.
• There is exactly one loop. It never crosses itself, never branches, and never leaves a loose end. Every corner it reaches, it must also leave.
• Tap an edge to draw it. Drag along several to draw a run. Use Rule out to mark an edge the loop cannot use — those crosses are how you make progress.
• Tap an edge again to clear it. On a desktop, right-click rules an edge out without switching modes.
• A number dims once it has the right count of lines, and turns red if too many are drawn. A corner where three lines meet is flagged as well — the loop can never fork.
• Every puzzle can be reasoned out from the clues alone — you never need to guess.

Where to start

• Rule out all four sides of every 0. That is free, and it gives its neighbours something to work with.
• A 3 next to a 0 is forced: the three sides away from the 0 must all be drawn.
• Two 3s side by side always have the edge between them drawn, plus the two outer edges opposite it.
• Watch the corners. If a corner already has one line and only one other way to go, the loop has to take it.
• Stuck? Hint finds the next edge logic settles, and says which clue proves it.