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| Commit | Line | Data |
|---|---|---|
| dbcc32e9 BA |
1 | p.boxed |
| 2 | | Pawns start on the 7th rank. Move a knight to promote them. | |
| 3 | ||
| 69f3d801 | 4 | h3 Divergences |
| dbcc32e9 | 5 | |
| 69f3d801 | 6 | p No castle, no en-passant capture. |
| dbcc32e9 BA |
7 | |
| 8 | p. | |
| 69f3d801 | 9 | ...Only the initial position changes, but this makes a huge difference. |
| dbcc32e9 BA |
10 | In particular, castling would be rather pointless so it's disabled here. |
| 11 | En-passant captures are impossible because all pawns already reached 7th rank. | |
| 12 | ||
| 69f3d801 | 13 | h3 About the initial position |
| dbcc32e9 BA |
14 | |
| 15 | p. | |
| 69f3d801 BA |
16 | Since truly random start can allow a mate in 3 with a knight, |
| 17 | the kings have at least one knight neighbor in the initial position. | |
| dbcc32e9 | 18 | This allows to move free out of potential check from the very beginning. |
| dbcc32e9 | 19 | |
| 5915f720 | 20 | p. |
| 69f3d801 BA |
21 | A less constraining condition would be to require the two knights to stand on |
| 22 | two squares of different colors, but it's not enough as proved by the | |
| 23 | following diagram. | |
| 24 | White can mate in 3: 1.Nc6 followed by Nb4 threatening both a2 and d3. | |
| 5915f720 | 25 | |
| dbcc32e9 BA |
26 | figure.diagram-container |
| 27 | .diagram | |
| 69f3d801 BA |
28 | | fen:RBN1BRRQ/PPPPPPP/8/4n3/8/8/Nppppppp/brkbqr1n: |
| 29 | figcaption After 1.Nc6 Nf3 2.Nb4 Ne5 (covers d3 but not a2) 3.Nxa2# | |
| dbcc32e9 BA |
30 | |
| 31 | h3 Source | |
| 32 | ||
| 33 | p | |
| 34 | | See for example the | |
| 35 | a(href="https://www.chessvariants.com/diffsetup.dir/upside.html") Upside down chess | |
| 36 | | page on chessvariants.com. |