This is my NXT version of the EV3 R3PTAR. And as you can see, it's takes a lot more parts than come with the standard NXT set. As the snake slithers around, the programming for the ultra sonic sensor tells the snake whether or not what it sees is moving or stationary. That way the snake knows whether to strike at or go around the obstacle.
About this creation
This is the original turning mechanism use in the original snake. It worked but skipped gears in certain situations. This also made re-centering using the touch sensor a bit imprecise.
The new turning mechanism uses no gears and is very precise. And offers a tighter turning radius. Handy when it's trying to turn out of a tight space.