Loopy is a logical puzzle game app.

You are given a grid of dots, marked with yellow lines to indicate which dots you are allowed to connect directly together.

Your aim is to use some subset of those yellow lines to draw a single unbroken loop from dot to dot within the grid.

The goal and rules of this game are simple.

1. Make a single continuous loop by connecting dots with vertical or horizontal lines.
2. The loop never crosses itself and never branches off.
3. The numbers of each block equals the number of lines surrounding it.
4. Empty blocks may be surrounded by any number of lines.