1. Make a single loop with lines passing through the centers of cells, horizontally,
   vertically, or changing direction. The loop never crosses itself, branches off,
   nor goes through the same cell twice.

2. The continuous dotted lines between black cells or to the outer frame are "Gates."
   The loop must pass all gates, but a gate can only be passed once.

3. The loop starts from the cell with the open numbered circle and returns to this cell.
   The number in the open circle shows the number of Gates to go through.

4. Numbers at the ends of Gates - in the black cells - show when the loop crosses
   the Gate. A gate without a number may be crossed at any point in the loop. For example,
   a Gate with a "1" must be the first crossed (in one of the directions) from
   the cell with the open circle.