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diff --git a/docs/chapter31/examples/TicTacToeGraphical.smp b/docs/chapter31/examples/TicTacToeGraphical.smp
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+++ b/docs/chapter31/examples/TicTacToeGraphical.smp
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+// Player is X, CPU is O. Squares are numbered left-to-right, top-to-bottom.
+// Graphical tic-tac-toe; the same strategy as TicTacToe.smp.
+// Click an empty square or press 1-9. R/Space replays; Q/Escape quits.
+// Pass any argument for a five-poll window smoke test.
+val main = { u8[~][] args ->
+    val screen = new sys.draw.Canvas(600,780);
+    val board = new u8[9];
+    _reset(board);
+    if( sys.gfx.open("Simple tic-tac-toe",screen.width,screen.height) != sys.gfx.OK ) return 1;
+    sys.audio.open(); // Audio is optional; failure leaves the game silent.
+    _draw(screen,board,-1);
+    int result = sys.gfx.present(screen.pixels);
+    bool mouseHeld = false, keyHeld = false, replayHeld = false;
+    int hover = -1, frames = 0;
+
+    while( result == sys.gfx.OK ) {
+        result = sys.gfx.wait(17);
+        if( result != sys.gfx.OK ) break;
+        if( sys.gfx.key('Q') ) break;
+        bool down = sys.gfx.button(sys.gfx.LEFT);
+        bool replay = sys.gfx.key('R') || sys.gfx.key(' ');
+        int square = _square(sys.gfx.mouseX(),sys.gfx.mouseY());
+        bool dirty = square != hover;
+        hover = square;
+        if( replay && !replayHeld ) { sys.audio.stop(); _reset(board); dirty = true; }
+        bool digit = false;
+        int choice = down && !mouseHeld ? square : -1;
+        for( int i = 0; i < 9; i++ ) {
+            int key = '1'+i;
+            if( sys.gfx.key(key) ) {
+                digit = true;
+                if( !keyHeld ) choice = i;
+            }
+        }
+        if( !(replay && !replayHeld) && _move(board,choice) ) {
+            sys.audio.play(_sound(board));
+            dirty = true;
+        }
+        mouseHeld = down;
+        keyHeld = digit;
+        replayHeld = replay;
+        if( dirty ) {
+            _draw(screen,board,hover);
+            result = sys.gfx.present(screen.pixels);
+        }
+        if( args# > 1 && ++frames == 5 ) break;
+    }
+    sys.audio.close();
+    sys.gfx.close();
+    return result == sys.gfx.ERROR ? 1 : 0;
+};
+
+// Called only for an accepted move; invalid input never requests a sound.
+val _sound = { u8[~] board ->
+    int winner = _winner(board);
+    return winner == 'X' ? sys.audio.WIN : winner == 'O' ? sys.audio.LOSE : sys.audio.BOOP;
+};
+
+val _reset = { u8[] board ->
+    for( int i = 0; i < 9; i++ ) board[i] = ' ';
+};
+val _square = { int x, int y ->
+    if( x < 48 || x >= 552 || y < 168 || y >= 672 ) return -1;
+    return (y-168)/168*3+(x-48)/168;
+};
+
+// One player turn followed by one CPU turn. Invalid/finished moves do nothing.
+val _move = { u8[] board, int square ->
+    if( square < 0 || square >= 9 || board[square] != ' ' || _finished(board) ) return false;
+    board[square] = 'X';
+    if( !_finished(board) ) {
+        int reply = _cpu(board);
+        if( reply >= 0 ) board[reply] = 'O';
+    }
+    return true;
+};
+
+val _finished = { u8[~] board ->
+    if( _winner(board) ) return true;
+    for( int i = 0; i < 9; i++ ) if( board[i] == ' ' ) return false;
+    return true;
+};
+
+val _winningLine = { u8[~] board ->
+    for( int i = 0; i < 3; i++ ) {
+        int row = i*3;
+        if( board[row] != ' ' && board[row] == board[row+1] && board[row] == board[row+2] ) return i;
+        if( board[i] != ' ' && board[i] == board[i+3] && board[i] == board[i+6] ) return 3+i;
+    }
+    if( board[4] != ' ' ) {
+        if( board[0] == board[4] && board[4] == board[8] ) return 6;
+        if( board[2] == board[4] && board[4] == board[6] ) return 7;
+    }
+    return -1;
+};
+// Return the winning mark, or zero.
+val _winner = { u8[~] board ->
+    int line = _winningLine(board);
+    return line < 0 ? 0 : line < 3 ? board[line*3] : line < 6 ? board[line-3] : board[4];
+};
+
+// Try each empty square, restoring it before returning.
+val _threat = { u8[] board, u8 mark ->
+    for( int i = 0; i < 9; i++ )
+        if( board[i] == ' ' ) {
+            board[i] = mark;
+            bool wins = _winner(board) == mark;
+            board[i] = ' ';       // Restore board
+            if( wins ) return i;
+        }
+    return -1;
+};
+// Win if possible, otherwise block, then prefer center, corners, and edges.
+// Called only after _finished has ruled out a full board.
+val _cpu = { u8[] board ->
+    // If O can win, do so
+    int win = _threat(board,'O');
+    if( win >= 0 ) return win;
+    // If X will win next move, block
+    int block = _threat(board,'X');
+    if( block >= 0 ) return block;
+    // If center is open, take it
+    if( board[4] == ' ' ) return 4;
+    // If a corner is open, take it
+    for( int i = 0; i < 9; i += 2 ) if( board[i] == ' ' ) return i;
+    // Take whatever is available
+    for( int i = 0; i < 9; i++ ) if( board[i] == ' ' ) return i;
+    return -1;
+};
+
+val _draw = { !sys.draw.Canvas screen, u8[~] board, int hover ->
+    u32 background = 0x142e36, paper = 0xf2eddf, ink = 0x35535a;
+    u32 cross = 0xe47b57, ring = 0x248b89, accent = 0xf0c778;
+    int winner = _winner(board);
+    bool finished = _finished(board);
+    screen.clear(background);
+    screen.text(48,34,"TIC TAC TOE",6,paper);
+    screen.fillRect(48,90,504,3,ink);
+    screen.text(48,116,finished ? (winner == 'X' ? "YOU WIN!" : winner == 'O' ? "CPU WINS" : "DRAW") : "YOUR TURN",4,accent);
+    screen.line(428,112,450,134,5,cross).line(450,112,428,134,5,cross);
+    screen.circle(496,123,13,5,0x70c9bf);
+    screen.text(428,145,"YOU",2,0xa2b9b7);
+    screen.text(484,145,"CPU",2,0xa2b9b7);
+    screen.fillRect(48,168,504,504,paper);
+    if( !finished && hover >= 0 && hover < 9 && board[hover] == ' ' )
+        screen.fillRect(48+(hover-hover/3*3)*168,168+hover/3*168,168,168,0xd9e8de);
+    for( int i = 1; i < 3; i++ ) {
+        screen.fillRect(48+i*168-3,168,6,504,ink);
+        screen.fillRect(48,168+i*168-3,504,6,ink);
+    }
+    for( int i = 0; i < 9; i++ ) {
+        int cx = 132+(i-i/3*3)*168, cy = 252+i/3*168;
+        if( board[i] == 'X' )
+            screen.line(cx-38,cy-38,cx+38,cy+38,12,cross).line(cx+38,cy-38,cx-38,cy+38,12,cross);
+        else if( board[i] == 'O' ) screen.circle(cx,cy,48,11,ring);
+        else screen.text(cx-6,cy-10,i == 0 ? "1" : i == 1 ? "2" : i == 2 ? "3" :
+            i == 3 ? "4" : i == 4 ? "5" : i == 5 ? "6" : i == 6 ? "7" : i == 7 ? "8" : "9",4,0x95a59e);
+    }
+    int line = _winningLine(board);
+    if( line >= 0 ) {
+        int first = line < 3 ? line*3 : line < 6 ? line-3 : line == 6 ? 0 : 2;
+        int last = line < 3 ? first+2 : line < 6 ? first+6 : line == 6 ? 8 : 6;
+        screen.line(132+(first-first/3*3)*168,252+first/3*168,132+(last-last/3*3)*168,252+last/3*168,5,0xeab64e);
+    }
+    screen.text(48,704,"CLICK A SQUARE OR PRESS 1-9",3,paper);
+    screen.text(48,738,"R OR SPACE REPLAY   Q OR ESC QUIT",3,0xa2b9b7);
+    screen.rect(48,168,504,504,3,ink);
+};