Look at the first image: the starting point was in the center, then down, right, up, left, down, left. This path is clearly wrong because there is no way to get the remaining squares
Look at the second image. The red dot must travel to the left and will not stop until it hits a wall. Then it must go up, right, up, right, down and right to complete the puzzle.
The essential questions: where is the starting point and where is the endpoint? Sometimes, neither is evident. There's a lot of trial and error.
What's good: there are only 30 levels and the game is free! (I've done 24 levels.)
What could be better: there is no undo button. Which means you have to start all over again. Also, ads pop up after you solve each level, but not when you restart a level.
Block Path - essentially the same thing
Snake Walk - essentially the same thing
Mortal Coil - this is a much better version. For a variety of reasons.
Stroke! - this version is similar but adds a color matching scheme that makes it devilishly hard.