This turtle is built only with parts from the NXT set.

The turtle just walks forward until something comes near the US sensor,
then the head retracts and the turtle hides for a few seconds.
If the object has disappeared the turtle will poke it's head out and walk on,
or if the object is still there the turtle will first turn around.
Also when a loud noise is detected during walking it will stop the head will 
retract for a few seconds.

I got the idea for the legs from Danny's design:
http://daniele.benedettelli.com/Turtle.htm
I tried rebuilding it from his photo's and added the US sensor myself.

If you have more questions, you can contact me at lego@zanthrax.nl
for the program, look here: http://zanthrax.nl/index.php?id=83

september 17 2006