ZigZag Puzzle. Red and black

Zigzag - is a logic game of searching of one possible path .
The purpose of the puzzle - to paint a square by one continuous line.
Some of the cells are already filled initially.
You can start from any free cell by clicking on it.
Next you specify the direction of the line . The line is drawn until it stops.
You can always cancel one last step (step back) or start the game again.
The "Solution"-button is available in all categories and at all levels. It is absolutely free and unlimited!