I was thinking on Langton's Ant -- what if we used different angles instead of the square, triangular, or hexagonal grids? The concept of drop/take flags would need to change, and that can be done with a distance parameter.
So I tried that, with code at Angled Langton's Ant. With an angle set of {-2 Pi/5, 2 Pi/5) and distance .15, the ant eventually makes a highway.
I tried various other angle sets, but that was the only highway I found. What other angle sets and distance parameters form highways?
Allowing multicolored flags for full turmite behavior, are there any angle / distance / rule sets that have interesting behavior?