Spiral Line Finder Problems

[Trynot]

Hi Guys -

I am trying to recreate Terry Griffin's Spiral Line Finder EV3 program from his book The Art of Lego Mindstorms EV3 Programming, chapter 10.

It begins with a one rotation forward move block and a 90 degree turn. The two move blocks are placed in a loop. A data wire increases the length of each forward move by a number of rotations equal to the loop index.

That's where it starts falling apart. I can get the bot to do an endless outward rectangular spiral, but Griffin does something weird with motor rotations to interrupt the spiral if a line is found.

I would really like to show the grade sixes and sevens I'm working with a robust program where there is a sensor reading inside a sophisticated pattern that exits a loop. If you are not familiar with the Griffin book, perhaps you have an alternative lesson suggestion. Remember they are grade 6/7 (mostly boys) so any ideas have to be kinetic!

Any ideas you can offer would be most appreciated!