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  <title>Seirawan Chess</title>
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  <h1>Seirawan Chess (S-Chess)</h1>

  <table cellpadding="20">
    <tr>
      <td>
        <img src="Seirawan.png">

        <p><i>Pieces available for gating will be displayed beside
        the board</i></p>
      </td>

      <td>
        <h3>Initial setup</h3>

        <p>e1, e8: King<br>
        d1, d8: Queen<br>
        a1, a8, h1, h8: Rook<br>
        c1, c8, f1, f8: Bishop<br>
        b1, b8, g1, g8: Knight<br>
        a2-h2, a7-h7: Pawns<br>
        <b>In each hand</b><br>
        1 Elephant<br>
        1 Hawk</p>
      </td>
    </tr>
  </table>

  <h3>Moves at a Glance</h3>

  <p>Click on a piece below to see its moves</p>

  <table class="board">
    <tr>
      <td class="h" id="sq0x9"></td>

      <td class="n" id="sq1x9" onmousedown="down_click(1,-9)"
      onmouseup="up_click()"><img src="sym/BlackRook.png"></td>

      <td class="n" id="sq2x9"></td>

      <td class="n" id="sq3x9"></td>

      <td class="n" id="sq4x9"></td>

      <td class="n" id="sq5x9" onmousedown="down_click(5,9)"
      onmouseup="up_click()"><img src="sym/BlackKing.png"></td>

      <td class="n" id="sq6x9"></td>

      <td class="n" id="sq7x9"></td>

      <td class="n" id="sq8x9" onmousedown="down_click(8,9)"
      onmouseup="up_click()"><img src="sym/BlackRook.png"></td>

      <td class="h" id="sq9x9"></td>

      <td class="h"><img src="sym/yellow.png"></td>

      <td class="w" rowspan="2" valign="top">
        <p>Sliding capture or non-capture,<br>
        can be blocked on any square along the ray</p>
      </td>
    </tr>

    <tr>
      <td class="h" id="sq0x8"></td>

      <td class="n" id="sq1x8"></td>

      <td class="n" id="sq2x8" onmousedown="down_click(2,0)"
      onmouseup="up_click()"></td>

      <td class="n" id="sq3x8"></td>

      <td class="n" id="sq4x8"></td>

      <td class="n" id="sq5x8"></td>

      <td class="n" id="sq6x8"></td>

      <td class="n" id="sq7x8"></td>

      <td class="n" id="sq8x8"></td>

      <td class="h" id="sq9x8"></td>
    </tr>

    <tr>
      <td class="h" id="sq0x7"></td>

      <td class="n" id="sq1x7"></td>

      <td class="n" id="sq2x7"></td>

      <td class="n" id="sq3x7"></td>

      <td class="n" id="sq4x7"></td>

      <td class="n" id="sq5x7"></td>

      <td class="n" id="sq6x7"></td>

      <td class="n" id="sq7x7"></td>

      <td class="n" id="sq8x7"></td>

      <td class="h" id="sq9x7"></td>

      <td class="h"><img src="sym/orange.png"></td>

      <td class="w">Unblockable leap (capture or non-capture)</td>
    </tr>

    <tr>
      <td class="h" id="sq0x6"></td>

      <td class="n" id="sq1x6"></td>

      <td class="n" id="sq2x6"></td>

      <td class="n" id="sq3x6"></td>

      <td class="n" id="sq4x6"></td>

      <td class="n" id="sq5x6" onmousedown="down_click(5,10)"
      onmouseup="up_click()"><img src="sym/WhiteHawk.png"></td>

      <td class="n" id="sq6x6"></td>

      <td class="n" id="sq7x6"></td>

      <td class="n" id="sq8x6"></td>

      <td class="h" id="sq9x6"></td>

      <td class="h"><img src="sym/green.png"></td>

      <td class="w">Non-capture only</td>
    </tr>

    <tr>
      <td class="h" id="sq0x5"></td>

      <td class="n" id="sq1x5"></td>

      <td class="n" id="sq2x5"></td>

      <td class="n" id="sq3x5"></td>

      <td class="n" id="sq4x5"></td>

      <td class="n" id="sq5x5"></td>

      <td class="n" id="sq6x5"></td>

      <td class="n" id="sq7x5"></td>

      <td class="n" id="sq8x5"></td>

      <td class="h" id="sq9x5"></td>

      <td class="h"><img src="sym/red.png"></td>

      <td class="w">Capture only</td>
    </tr>

    <tr>
      <td class="h" id="sq0x4"></td>

      <td class="n" id="sq1x4"></td>

      <td class="n" id="sq2x4"></td>

      <td class="n" id="sq3x4"></td>

      <td class="n" id="sq4x4"></td>

      <td class="n" id="sq5x4" onmousedown="down_click(-5,4)"
      onmouseup="up_click()"><img src="sym/WhiteElephant.png"></td>

      <td class="n" id="sq6x4"></td>

      <td class="n" id="sq7x4"></td>

      <td class="n" id="sq8x4"></td>

      <td class="h" id="sq9x4"></td>
    </tr>

    <tr>
      <td class="h" id="sq0x3"></td>

      <td class="n" id="sq1x3" onmousedown="down_click(1,3)"
      onmouseup="up_click()"><img src="sym/BlackPawn.png"></td>

      <td class="n" id="sq2x3" onmousedown="down_click(2,3)"
      onmouseup="up_click()"><img src="sym/WhitePawn.png"></td>

      <td class="n" id="sq3x3" onmousedown="down_click(3,3)"
      onmouseup="up_click()"><img src="sym/WhiteRook.png"></td>

      <td class="n" id="sq4x3" onmousedown="down_click(4,3)"
      onmouseup="up_click()"><img src="sym/WhiteKnight.png"></td>

      <td class="n" id="sq5x3" onmousedown="down_click(5,3)"
      onmouseup="up_click()"><img src="sym/WhiteQueen.png"></td>

      <td class="n" id="sq6x3" onmousedown="down_click(6,3)"
      onmouseup="up_click()"><img src="sym/WhiteBishop.png"></td>

      <td class="n" id="sq7x3" onmousedown="down_click(7,3)"
      onmouseup="up_click()"><img src="sym/WhiteKing.png"></td>

      <td class="n" id="sq8x3"></td>

      <td class="h" id="sq9x3"></td>
    </tr>

    <tr>
      <td class="h" id="sq0x2"></td>

      <td class="n" id="sq1x2"></td>

      <td class="n" id="sq2x2"></td>

      <td class="n" id="sq3x2"></td>

      <td class="n" id="sq4x2"></td>

      <td class="n" id="sq5x2"></td>

      <td class="n" id="sq6x2"></td>

      <td class="n" id="sq7x2"></td>

      <td class="n" id="sq8x2"></td>

      <td class="h" id="sq9x2"></td>
    </tr>

    <tr>
      <td class="h" id="sq0x1"></td>

      <td class="n" id="sq1x1"></td>

      <td class="n" id="sq2x1" onmousedown="down_click(-2,1)"
      onmouseup="up_click()"><img src="sym/WhitePawn.png"></td>

      <td class="n" id="sq3x1"></td>

      <td class="n" id="sq4x1"></td>

      <td class="n" id="sq5x1"></td>

      <td class="n" id="sq6x1"></td>

      <td class="n" id="sq7x1"></td>

      <td class="n" id="sq8x1"></td>

      <td class="h" id="sq9x1"><img src="sym/WhiteElephant.png"></td>
    </tr>

    <tr>
      <td class="h" id="sq0x0"></td>

      <td class="n" id="sq1x0"></td>

      <td class="n" id="sq2x0"></td>

      <td class="n" id="sq3x0"></td>

      <td class="n" id="sq4x0"></td>

      <td class="n" id="sq5x0"></td>

      <td class="n" id="sq6x0"></td>

      <td class="n" id="sq7x0" onmousedown="down_click(7,0)"
      onmouseup="up_click()"><img src="sym/WhiteKnight.png"></td>

      <td class="n" id="sq8x0"></td>

      <td class="h" id="sq9x0"><img src="sym/WhiteHawk.png"></td>
    </tr>
  </table>

  <p id="piece" height="20">:<br>
  :<br>
  :<br>
  :</p>

  <table cellpadding="5" border="1">
    <tr>
      <td>Piece</td>

      <td>ID</td>

      <td>value</td>

      <td>Moves (<a href="Betza.html">Betza notation</a>)</td>

      <td>Remarks</td>
    </tr>

    <tr>
      <td>King</td>

      <td>K</td>

      <td>-</td>

      <td>K</td>

      <td>Can castle with Rook, moving 3 steps towards it</td>
    </tr>

    <tr>
      <td>Queen</td>

      <td>Q</td>

      <td>9.5</td>

      <td>RB or Q</td>

      <td></td>
    </tr>

    <tr>
      <td>Elephant</td>

      <td>E</td>

      <td>9</td>

      <td>RN</td>

      <td></td>
    </tr>

    <tr>
      <td>Hawk</td>

      <td>H</td>

      <td>8.75</td>

      <td>BN</td>

      <td></td>
    </tr>

    <tr>
      <td>Rook</td>

      <td>R</td>

      <td>5</td>

      <td>R</td>

      <td></td>
    </tr>

    <tr>
      <td>Bishop</td>

      <td>B</td>

      <td>3.5</td>

      <td>B</td>

      <td>Color-bound</td>
    </tr>

    <tr>
      <td>Knight</td>

      <td>N</td>

      <td>3</td>

      <td>N</td>

      <td></td>
    </tr>

    <tr>
      <td>Pawn</td>

      <td>P</td>

      <td>1</td>

      <td>mfWcfF</td>

      <td>Promotes to Q, E, H, R, B, or N on reaching last
      rank</td>
    </tr>
  </table>

  <h3>Pawn peculiarities</h3>

  <ul>
    <li>Pawns capture differently from how they move (straight
    move, diagonal capture).</li>

    <li>Pawns can move two squares ahead from their initial
    position, provided they are not blocked.</li>

    <li>On the move immediately after such a double push, they can
    be captured en passant by another Pawn, as if they had only
    moved 1 square ahead.</li>

    <li>Pawns promote to any other (non-royal) piece of choice when
    they reach last rank.</li>
  </ul>

  <h3>Castling</h3>

  <p>A King that has not moved before can move <b>three</b> squares
  in the direction of a Rook that has not moved before, in which
  case that Rook is moved to the square next to the King on the
  other side. This is only allowed if all squares between King and
  Rook are empty, when the King is not in check on the square it
  came from, and would not be in check on any of the squares it
  skipped over.</p>

  <h3>General rules</h3>

  <ul>
    <li>It is not allowed to expose your King to check.</li>

    <li>The game is won by checkmating the opponent's King.</li>

    <li>Stalemate (no legal moves, but not in check) is a
    draw.</li>

    <li>The Elephant or Hawk can be 'gated' into play, by placing
    them on a square evacuated by a back-rank piece that moved for
    the first time, as second part of the same turn.</li>

    <li>During gating, your King must not 'pass through
    check'.</li>

    <li>When castling, you can gate onto the King or Rook square,
    but not on both.</li>
  </ul>

  <h3>XBoard interface issues</h3>

  <p>To perform a gating move, first select the piece to be gated.
  (When you have not switched off highlighting or the line gap,
  this will draw a yellow border around the piece.) Then move the
  piece on the back rank. If you drag the piece, the gated piece
  will appear from under it. (With click-click moving you will only
  see it after the move is already done.) To gate on the Rook
  square after castling, you have to enter the castling by dragging
  the Rook onto the King!</p>

  <p>To enter a gating move by typing, you have to suffix them with
  /H or /E. For gating on the Rook square after castling, you would
  have to write the castling as RxK. (Ughh! Good thing that no one
  in his right mind would want to gate there!)</p>

  <h3>Differences with FIDE</h3>

  <p>The Elephant and Hawk pieces are extra, and enter the board by
  gating.</p>

  <h3>Strategy issues</h3>

  <p>It is not possible to force checkmate on a bare King with just
  a single Bishop or Knight (in addition to your own King). Two
  Knights cannot do that either. The Archbishop can force checkmate
  against a bare King.</p>

  <p>Bishops are confined to squares of a single color. Having
  Bishops on both colors compensates this weakness, and is worth an
  extra 0.5 on top of their added value.</p>

  <p>As Elephant and Hawk are nearly equal in value to Queen,
  under-promotion is very common.</p>

  <p>The super-pieces (Q, E, H) devaluate by the presence of
  lower-valued opponent pieces. As a result trading Q for R + B is
  in general a good trade when you still have E and H, as the
  latter gain in value by eliminating the opponent's R and B, which
  is more compensation than the intrinsic value difference between
  Q and R + B.</p>

  <p>Keeping E and H in hand is good if there are still many gating
  opportunities, as you can then gate at the location that is most
  damaging to your opponents position. When there are not too many
  positions left, protecting the remaining ones becomes a
  vulnerability, however, so you better use them were you still
  can. If you still have a piece in hand, and only a single Knight
  that can gate it (bacause all your other pieces already moved),
  even sacrificing a Queen for that Knight would gain your opponent
  a piece.</p>
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