Fill Line : one line puzzle game Guide

How the game works

Fill Line asks for one unbroken route through every square on the grid. The route begins at a designated block, cannot overlap itself, and cannot revisit a filled square. That means a locally open move can still seal off an isolated pocket later. The useful question is not simply where the line can go next, but whether every remaining region will still be reachable afterward.

Controls

Start on the marked block and drag through adjacent empty blocks. The line cannot overlap itself or revisit a filled block, so the route must cover the board in one continuous pass.

Practical tips

• Clear narrow dead-end corridors before closing the route around them.
• Avoid splitting the unfilled area into two regions with only one entrance.
• Work backward mentally from isolated corner squares when the path is unclear.

Before you start

Drag from the starting block through adjacent squares without lifting, crossing the route, or revisiting a square.