Chess solutions
1. White selfmates in 7
1. a7-a8=N g4-g3
2. Nf2-h3+ Ke3-d3
3. Rc4-g4 g3-g2
4. Na8-c7 g2xh1
Continuations according to promotion in the 4th set:
Rook
5. Nh3-f4+ Kd3-c4
6. Nf4-d5+ Kc4-d3
7. Qg1-f1+ Rh1xf1X
Queen
5. Rb5-d5+ Qh1xd5
6. Qg1-f1+ Kd3-e3
7. Ba5xd2+ Qd5xd2X
Knight
5. Qg1-e3+ Kd3xe3
6. Rb5-e5+ Ke3-d3
7. Nh3-f2+ Nh1xf2X
Bishop
5. Qg1-f1+ Kd3-e3
6. Nc7-d5+ Bh1xd5
7. Rb5-b3+ Bd5xb3X
2. White mates in 2
1. Qh8
3. White mates in 2
1. Nb3
4. White mates in 2
1. Nc3