How Koga decides
- Interference (also called obstruction) happens when a piece is placed on a line that a rook, bishop, or queen needs in order to guard one of its own pieces.
- Once that line is cut, the piece behind the block loses its defender and can be won.
- The point is geometric: a single block on the right square severs the connection between the long-range guard and the thing it was protecting.
- Active interference — our own move lands on a square that sits on an enemy rook, bishop, or queen's line, cutting that piece off from a friendly piece it was defending.
- Forced (self-inflicted) interference — looking a few moves into the engine's main line, the opponent is forced to play a move that blocks one of THEIR OWN long-range pieces, abandoning the defence of a square our follow-up move then exploits.
- In both cases the blocking piece is the interfering piece, the long-range piece behind it is the one cut off, and the now under-defended square is the target.
- Cutting a line is not enough on its own. The piece that loses its guard must actually become winnable — after the block it must have MORE attackers than defenders.
- If the cut-off piece is still adequately defended by something else, nothing real has been won, so it is not reported.
- For the forced pattern the same line must genuinely disappear: the opponent's blocking move has to be the thing that severs the defence of the square our next move attacks.
Test positions (the examples that guard against regressions)
Golden puzzles — every real Lichess puzzle Koga is tested against for this tactic (9)
Lichess 07YoN
Lichess 07YoN (rating 1296). Solution: Rxh3+ Kg7 Rxg2+.
Koga flags interference as a follow-up here — it fires later in the line, on Kg7, not on the move shown above.
Lichess 000h0
Lichess 000h0 (rating 2053). Solution: Rxf3 gxf3 Qxh2+ Kf1 Qh3+ Ke2 Qxe6+.
Koga flags interference as a follow-up here — it fires later in the line, on Ke2, not on the move shown above.
Lichess 0P1vH
Lichess 0P1vH (rating 1983). Solution: Qh8+ Ke7 Rxg7+ Kd6 Qd8+ Ke5 Qxc7+.
Koga flags interference as a follow-up here — it fires later in the line, on Ke7, not on the move shown above.
Lichess 0EywV
Lichess 0EywV (rating 1360). Solution: Bd4 Qa3 Bxe5.
Lichess 0B5Yp
Lichess 0B5Yp (rating 1255). Solution: Nxh4+ Kg4 Nxg6.
Koga flags interference as a follow-up here — it fires later in the line, on Kg4, not on the move shown above.
Lichess 0OEiy
Lichess 0OEiy (rating 1753). Solution: Rg5+ Kh4 Rxh8#.
Koga flags interference as a follow-up here — it fires later in the line, on Kh4, not on the move shown above.
Lichess 0KjQI
Lichess 0KjQI (rating 1427). Solution: Qd7 Nc7 Qxc8+.
Koga flags interference as a follow-up here — it fires later in the line, on Nc7, not on the move shown above.
Lichess 0PG0S
Lichess 0PG0S (rating 2021). Solution: Nf5+ exf5 Qe5+ Kf8 Qxh8+.
Koga flags interference as a follow-up here — it fires later in the line, on Kf8, not on the move shown above.
Lichess 0BN1T
Lichess 0BN1T (rating 1603). Solution: Bc3+ Kd1 Qxb1+.
Koga flags interference as a follow-up here — it fires later in the line, on Kd1, not on the move shown above.