[Retros] Add-on

[afretro]

Mate to the black king on b1:
1.Pc2-c3   Pf7-f6   2.Qd1-a4   Ke8-f7   3.Qa4xa7   Kf7-e6   
4.Pa2-a4   Ke6-d5   5.Ra1-a2   Kd5-c4   6.Pb2-b3   Kc4xb3   
7.Qa7-c5   Kb3xa2   8.Qc5-a3   Ka2xb1   9.Qa3-b2   

Thus it has been proven that in a dual-free SPG the black king can be mated on any first-rank square in just 17 single moves.

Best,
Andrey