Goal: Draw a single continuous closed loop on the grid edges.
Numbers: Every numbered cell must be inside the loop. The number tells you how many cells are visible from that cell in all 4 directions (up, down, left, right) within the loop, including the cell itself.
Controls: Click/tap an edge to draw or erase it. Right-click or long-press to mark an edge with an X (definitely empty).
Loop Rules: The loop must be a single closed path. No branches, no crossings, no loose ends.
Tips: Start with cells that have large or small numbers. A 1 means the cell is isolated. A large number means long straight sections of the loop.