You are given a 17x15 board with some positions marked black. The black squares are the possible positions of fence posts.
You will have to build a continuous loop of fence by adding pieces of fence between the black fence post positions.
Click board to randomize the setup. Numbers will appear at some fence post positions. These number show the SUM of the two pieces of straight fence which originate at that position.
Note that these marked positions do not have to be corners of the fence.
Also, two posts with numbers should never be part of the same straight piece of fence.

Click a position between two black squares to place a piece of fence. The system will add nice fence posts automatically.
Click an existing piece of fence to delete it.
If the lengths at the numbered positions are wrong the numbers will be displayed in red, otherwise in blue.

Click the botton at the top right border to see the solution.
Note that usually several solutions are possible.

You win if
- your fence is a closed loop which includes all given fence posts.
- all numbers are blue; i.e., all given lengths of fence are correctly constructed.

Variant 2:
Here the length of your fence must be the same as the one given by the system.
The fence length counters are at the right border.

Please note there are three alternative piece sets.

 
This game was inspired by a mathematical problem stated in 2005 at the PQRST puzzle competition (http://www.otuzoyun.com/pqrst).