{{explanation}}
3s & 4s start on opp sides

1-8
: All set & 1s+2s also 3s+4s dance 1/2 RH across, all set & 2s+1s also
  4s+3s dance 1/2 LH across
9-16
: 1s+4s chase anticlockwise 1/2 way **while** 2s+3s dance 1/2 R&L, 4s+3s
  also 2s+1s set facing on sides & 1/2 turn RH. (3)(4)(1)(2)
17-24
: All dance RSh reels of 4 on sides
25-32
: 3s & 2s 1/2 turn RH **while** 4s+1s dance 1/2 R&L, 1s & 4s dance out
  ends & cast in 1 place. 3 1 (4) (2)