Hutenplatz means "knights place", and it is meant to be like a war.
Your pieces are knights, and there are walls throughout the board.
You can generate a new board by clicking the "New" button.
Anyhow, lets get to how you actually play the game.
You click on a knight to select it, then click on an empty square to go there.
You can move up to 2 squares in any direction.
If you move to a neighbouring square, then your knight will be replicated, as a new one is added to your army.
After your move all neighbouring knights of the opponent will turn colour and be yours.
This means that you have captured the knights, and put them in your army.
The player who ends with the most knights of his colour, has won the crusade.