Each person stops turning (but otherwise continues moving)
after having turned the given fraction. If you turn one way and then the other,
all of those turns add up.
\phfour{b1n,g1s,g2n,b2s}
\phfour{g1n,b2w,b1e,g2s}
before 3/4 Stable Swing Thru
after
This can lead to the necessity to know call definitions quite rigorously: