No.760 (ND)
No.760 by Nicolas Dupont – PG problem with Extinction Chess shown for the first time on JF! (JV)
Definition:
Extinction Chess: A side is in check if it is threatened to no more have a kind of piece it owned in the diagram position. Promotions to King are allowed.
No.760 Nicolas Dupont France original – 27.03.2015 After Joost De Heer

Solution: (click to show/hide)

white Bf1c1 Ke1 Qd1 Ph2g2f2e2d2c2b2a2 Sg1b1 Rh1a1
black Bf8c8 Ke8 Qd8 Ph7g7f7e7d7c7b7a7 Sg8b8 Rh8a8
PG20 (12+14) Extinction Chess

1.a2a4 e7e5 2.a4a5 Qd8h4 3.a5a6 Sg8e7 4.a6*b7 Sb8a6 5.b7b8=K Bc8b7 {
} 6.f2f4 Bb7d5 7.f4f5 Se7c6 8.f5f6 Bf8e7 9.f6*g7 Ra8*b8 + 10.g7g8=K Rb8b4 {
} 11.g2g4 Rb4c4 12.b2b4 f7f5 13.b4b5 f5f4 14.b5b6 f4f3 15.b6b7 Rh8*g8 + {
} 16.b7b8=K Rg8g6 17.g4g5 Rg6d6 18.g5g6 f3f2 19.g6g7 Sa6*b8 + 20.g7g8=K Bd5*g8 #
The thematic content shows 4 Schnoebelen white Kings (promoted pieces captured without having moved). This idea belongs to Joost De Heer, R302 Probleemblad 2006, but with only 2 such Kings. The solution is fully economic regarding the number of moves  each white move is thematic  and also regarding the number of captures – the thematic content can’t be shown with fewer than 6 captures.
This is not fully computer tested but sound in 2 steps (until move 11.0 and from move 11.0 to the end) by Popeye 4.55 (version 4.69 is buggy concerning Extinction Chess). I’m far from being sure that the entire sequence remains sound, as the strategy is dangerous with the 2 black Rooks playing along 2 thematic white Pawns lines. For example this is cooked with 19…Sc6xb8+ instead of 16…Sa6xb8+ (left as an exercise for the interested reader).
Finally note that I used the “De Heer definition” of Extinction Chess – which is also the one followed by solving programs. The original definition from Schmittberger quoted by Pritchard (see the encyclopedia of chess variants) appears to be less convenient for the problem world. By the way, it seems that my entry is the very first one in Julia’s Fairies dealing with this fairy condition! (Author)

The problem published by Joost (Probleemblad 2006) is: 1. f4 e5 2. f5 Bc5 3. f6 Se7 4. fxg7 Bf2+ 5. g8=K c5 6. a4 Qb6 7. a5+ Qb5 8. a6 Sbc6 9. axb7 Rxg8+ 10. b8=K Rxb8+. Nicolas just made a significant improvement.
Is this a cook?
10… f5 11. b4 Rxb4 12. Kh8 Rc4 13. Kg8 and black moves same as in solution, white moves his second king around with 20. Kg8 Bxg8# at the end.
I meant Kg7 instead of Kh8 of course.
1. a4 e5 2. a5 Qh4 3. a6 Se7 4. axb7 Sa6 5. b8=K Bb7 6. f4 Bd5 7. f5 Sc6 8. f6 Be7 9. fxg7 Rxb8+ 10. g8=K f5 11. b4 Rxb4 12. Kg7 Rc4 13. Kh6 Rg8 14. g4 Sab8 15. g5 f4 16. g6 Rxg6 17. Kg7 Rd6 18. Kg8 f3 19. Kg7 f2 20. Kg8 Bxg8#
Yes, I was about to say that the wPg2 must also be captured, but this is indeed possible… If you are able to use my ideas to find a correction Joost, maybe we could then publish it as a joint.