Trees: Martian Road Signs-A Dichotomous Key

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1.  If the sign is a circle, go to 2.

     If not, go to 7. 

2.  If the sign contains other circles, go to 3.

     If not, go to 4. 

3.  If the circle contains only one circle:  Dragon Cemetery.

     If the circle contains two circles:  Watch for Falling Eggs

4.  If circle contains only one straight line, go to 5.

     If not, go to 6. 

5.  If line is horizontal:  Flying Saucer Crossroad.

     If line is vertical:  Divided Highway 

6.  If lines make an X:  Dragon Crossing.

     If lines make an M:  Watch for Dragons Landing. 

7.  If sign is T-shaped at any position, go to 8.

     If not, go to 11. 

8.  If T is horizontal or sideways, go to 9.

     If not, go to 11. 

9.  If T handle points left:  No Right Turn.

     If T handle points right:  No Left Turn. 

10.  If T handle is in normal T position:  road Ends, Must turn Left or Right.      

11.  If sign is triangular, go to 12.

       If not, go to 13. 

12.  If triangle point is down:  Long Downhill Road.

       Of triangle points upward:  Long Uphill Road. 

13.  If sign is diagonal or leaning, go to 14.

       If not, go to 15. 

14.  If sign leans to the right:  Watch for Dragons Entering from Right.

       If sign leans to the left:  Watch for Dragons Entering from the Left.

15.  If sign is square or nearly so:  Slow (1/2 Standard Speed).

       If sign is not a square, go to 16. 

16.  If sign is a horizontal rectangle:  Standard Speed Limit.

       If sign is a vertical rectangle:  Double Standard Speed.