Slide the grid squares around so that they all join up into a single connected network with no loops.
Click on the arrows at the edges of the grid to move a row or column left, right, up or down. The square that falls off the end of the row comes back on the other end.
Squares connected to the middle square are lit up. Aim to light up every square in the grid (not just the endpoint blobs).
Connecting across a red barrier line is forbidden. On harder levels, there are fewer barriers, which makes it harder rather than easier!