Create Portals
If you quickly draw a perfect circle, you will create a portal. You can create multiple portals, then send a line through one. It will emerge from the other, which you can use to your advantage on some of the trickier puzzles. If you decide that a portal is just in the way, tap it to remove it.
Horizontal Edges
You lose if you draw a line that exits from the top or bottom of the screen, so it's important to avoid that when possible. However, the left and right horizontal edges are a different matter, an in fact you can use them as part of your strategy. Since a line will generally keep going until it exits along the top or bottom of the screen (or runs into a colored dot), you can let it rebound from the edge of the screen and it could keep going to help you solve the puzzle.
Overshooting
When a line overshoots the dots to the left or right, it may bounce back and collect the dots while returning. However there is no such "wall" on the top or bottom. Your line will continue as long as possible (until touching a black dot or moves off the top or bottom).
