Click the board. A system of walls representing a house will appear. You have to visit all doors apart from two. There are red and blue doors. You can enter each door only once, and you have to alternate the colour of the doors.

A display on the right border shows how many door you have to walk through. A counter will show you how many doors you have already walked through. When these two numbers are the same, you win.

 
The code of this program uses an interesting 'dynamic board setup': Instead of defining each wall position in the board setup, I let a random player built the house walls (giving it only the start- and end-positions of each wall).

More freeware and real puzzles and games at my homepage: http://karl.kiwi.gen.nz.