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The world starts off black, with as many turtles created in the center as is specified by the num-turtles slider. The first 4 turtles face 0, 90, 180 and 270 degrees respectively. The directions of the other turtles is generated by Netlogo. The turtles move forward by the number of units specified in move-forward, and if the patch they land on is black, they turn the patch color to white and rotate 90 degrees right. Otherwise, it turns it sky and rotates left 90 degrees. At the same time, it changes the color of the patch that is 30 units in the x direction and 30 units in the y direction to yellow too.

- The num-turtles slider determine how many turtles to create initially.

- The move-forward slider says how many units each turtle should move forward by.

- Only the first 4 turtles have a specific direction. The rest are generated by Netlogo. Use the seed slider to yield the same sequence every time.

- The setup button clears the screen and creates the number of turtles set by num-turtles slider.

- Click on go forever to see the pattern produced.

For 4 turtles, the pattern produced will always be the same, no matter where the seed slider is at. This is because the direction of the first 4 turtles is set - it isn't determined by Netlogo.