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Tetris source code

<!-- MIT License https://github.com/jakesgordon/javascript-tetris/blob/master/LICENSE -->

<script>
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</script>

<style>
    body      { font-family: Helvetica, sans-serif; }
    #tetris   { margin: 1em auto; padding: 1em; border: 4px solid black; border-radius: 10px; background-color: #F8F8F8; }
    #stats    { display: inline-block; vertical-align: top; }
    #canvas   { display: inline-block; vertical-align: top; background: url(texture.jpg); box-shadow: 10px 10px 10px #999; border: 2px solid #333; }
    #menu     { display: inline-block; vertical-align: top; position: relative; }
    #menu p   { margin: 0.5em 0; text-align: center; }
    #menu p a { text-decoration: none; color: black; }
    #upcoming { display: block; margin: 0 auto; background-color: #E0E0E0; }
    #score    { color: red; font-weight: bold; vertical-align: middle; }
    #rows     { color: blue; font-weight: bold; vertical-align: middle; }
    #stats    { position: absolute; bottom: 0em; right: 1em; }
    @media screen and (min-width:   0px) and (min-height:   0px)  { #tetris { font-size: 0.75em; width: 250px; } #menu { width: 100px; height: 200px; } #upcoming { width:  50px; height:  50px; } #canvas { width: 100px; height: 200px; } } /* 10px chunks */
    @media screen and (min-width: 400px) and (min-height: 400px)  { #tetris { font-size: 1.00em; width: 350px; } #menu { width: 150px; height: 300px; } #upcoming { width:  75px; height:  75px; } #canvas { width: 150px; height: 300px; } } /* 15px chunks */
    @media screen and (min-width: 500px) and (min-height: 500px)  { #tetris { font-size: 1.25em; width: 450px; } #menu { width: 200px; height: 400px; } #upcoming { width: 100px; height: 100px; } #canvas { width: 200px; height: 400px; } } /* 20px chunks */
    @media screen and (min-width: 600px) and (min-height: 600px)  { #tetris { font-size: 1.50em; width: 550px; } #menu { width: 250px; height: 500px; } #upcoming { width: 125px; height: 125px; } #canvas { width: 250px; height: 500px; } } /* 25px chunks */
    @media screen and (min-width: 700px) and (min-height: 700px)  { #tetris { font-size: 1.75em; width: 650px; } #menu { width: 300px; height: 600px; } #upcoming { width: 150px; height: 150px; } #canvas { width: 300px; height: 600px; } } /* 30px chunks */
    @media screen and (min-width: 800px) and (min-height: 800px)  { #tetris { font-size: 2.00em; width: 750px; } #menu { width: 350px; height: 700px; } #upcoming { width: 175px; height: 175px; } #canvas { width: 350px; height: 700px; } } /* 35px chunks */
    @media screen and (min-width: 900px) and (min-height: 900px)  { #tetris { font-size: 2.25em; width: 850px; } #menu { width: 400px; height: 800px; } #upcoming { width: 200px; height: 200px; } #canvas { width: 400px; height: 800px; } } /* 40px chunks */
</style>

<br />
<div id="tetris">
<div id="menu">
<div id="start">
<a href="javascript:play();">Press Space to Play.</a></div>
<canvas id="upcoming"></canvas><br />
score <span id="score">00000</span><br />
rows <span id="rows">0</span></div>
<canvas id="canvas">
      Sorry, this example cannot be run because your browser does not support the &lt;canvas&gt; element
    </canvas>
  </div>
<script>
    //-------------------------------------------------------------------------
    // base helper methods
    //-------------------------------------------------------------------------
    function get(id)        { return document.getElementById(id);  }
    function hide(id)       { get(id).style.visibility = 'hidden'; }
    function show(id)       { get(id).style.visibility = null;     }
    function html(id, html) { get(id).innerHTML = html;            }
    function timestamp()           { return new Date().getTime();                             }
    function random(min, max)      { return (min + (Math.random() * (max - min)));            }
    function randomChoice(choices) { return choices[Math.round(random(0, choices.length-1))]; }
    if (!window.requestAnimationFrame) { // http://paulirish.com/2011/requestanimationframe-for-smart-animating/
      window.requestAnimationFrame = window.webkitRequestAnimationFrame ||
                                     window.mozRequestAnimationFrame    ||
                                     window.oRequestAnimationFrame      ||
                                     window.msRequestAnimationFrame     ||
                                     function(callback, element) {
                                       window.setTimeout(callback, 1000 / 60);
                                     }
    }
    //-------------------------------------------------------------------------
    // game constants
    //-------------------------------------------------------------------------
    var KEY     = { ESC: 27, SPACE: 32, LEFT: 37, UP: 38, RIGHT: 39, DOWN: 40 },
        DIR     = { UP: 0, RIGHT: 1, DOWN: 2, LEFT: 3, MIN: 0, MAX: 3 },
        stats   = new Stats(),
        canvas  = get('canvas'),
        ctx     = canvas.getContext('2d'),
        ucanvas = get('upcoming'),
        uctx    = ucanvas.getContext('2d'),
        speed   = { start: 0.6, decrement: 0.005, min: 0.1 }, // how long before piece drops by 1 row (seconds)
        nx      = 10, // width of tetris court (in blocks)
        ny      = 20, // height of tetris court (in blocks)
        nu      = 5;  // width/height of upcoming preview (in blocks)
    //-------------------------------------------------------------------------
    // game variables (initialized during reset)
    //-------------------------------------------------------------------------
    var dx, dy,        // pixel size of a single tetris block
        blocks,        // 2 dimensional array (nx*ny) representing tetris court - either empty block or occupied by a 'piece'
        actions,       // queue of user actions (inputs)
        playing,       // true|false - game is in progress
        dt,            // time since starting this game
        current,       // the current piece
        next,          // the next piece
        score,         // the current score
        vscore,        // the currently displayed score (it catches up to score in small chunks - like a spinning slot machine)
        rows,          // number of completed rows in the current game
        step;          // how long before current piece drops by 1 row
    //-------------------------------------------------------------------------
    // tetris pieces
    //
    // blocks: each element represents a rotation of the piece (0, 90, 180, 270)
    //         each element is a 16 bit integer where the 16 bits represent
    //         a 4x4 set of blocks, e.g. j.blocks[0] = 0x44C0
    //
    //             0100 = 0x4 << 3 = 0x4000
    //             0100 = 0x4 << 2 = 0x0400
    //             1100 = 0xC << 1 = 0x00C0
    //             0000 = 0x0 << 0 = 0x0000
    //                               ------
    //                               0x44C0
    //
    //-------------------------------------------------------------------------
    var i = { size: 4, blocks: [0x0F00, 0x2222, 0x00F0, 0x4444], color: 'cyan'   };
    var j = { size: 3, blocks: [0x44C0, 0x8E00, 0x6440, 0x0E20], color: 'blue'   };
    var l = { size: 3, blocks: [0x4460, 0x0E80, 0xC440, 0x2E00], color: 'orange' };
    var o = { size: 2, blocks: [0xCC00, 0xCC00, 0xCC00, 0xCC00], color: 'yellow' };
    var s = { size: 3, blocks: [0x06C0, 0x8C40, 0x6C00, 0x4620], color: 'green'  };
    var t = { size: 3, blocks: [0x0E40, 0x4C40, 0x4E00, 0x4640], color: 'purple' };
    var z = { size: 3, blocks: [0x0C60, 0x4C80, 0xC600, 0x2640], color: 'red'    };
    //------------------------------------------------
    // do the bit manipulation and iterate through each
    // occupied block (x,y) for a given piece
    //------------------------------------------------
    function eachblock(type, x, y, dir, fn) {
      var bit, result, row = 0, col = 0, blocks = type.blocks[dir];
      for(bit = 0x8000 ; bit > 0 ; bit = bit >> 1) {
        if (blocks & bit) {
          fn(x + col, y + row);
        }
        if (++col === 4) {
          col = 0;
          ++row;
        }
      }
    }
    //-----------------------------------------------------
    // check if a piece can fit into a position in the grid
    //-----------------------------------------------------
    function occupied(type, x, y, dir) {
      var result = false
      eachblock(type, x, y, dir, function(x, y) {
        if ((x < 0) || (x >= nx) || (y < 0) || (y >= ny) || getBlock(x,y))
          result = true;
      });
      return result;
    }
    function unoccupied(type, x, y, dir) {
      return !occupied(type, x, y, dir);
    }
    //-----------------------------------------
    // start with 4 instances of each piece and
    // pick randomly until the 'bag is empty'
    //-----------------------------------------
    var pieces = [];
    function randomPiece() {
      if (pieces.length == 0)
        pieces = [i,i,i,i,j,j,j,j,l,l,l,l,o,o,o,o,s,s,s,s,t,t,t,t,z,z,z,z];
      var type = pieces.splice(random(0, pieces.length-1), 1)[0];
      return { type: type, dir: DIR.UP, x: Math.round(random(0, nx - type.size)), y: 0 };
    }
    //-------------------------------------------------------------------------
    // GAME LOOP
    //-------------------------------------------------------------------------
    function run() {
      showStats(); // initialize FPS counter
      addEvents(); // attach keydown and resize events
      var last = now = timestamp();
      function frame() {
        now = timestamp();
        update(Math.min(1, (now - last) / 1000.0)); // using requestAnimationFrame have to be able to handle large delta's caused when it 'hibernates' in a background or non-visible tab
        draw();
        stats.update();
        last = now;
        requestAnimationFrame(frame, canvas);
      }
      resize(); // setup all our sizing information
      reset();  // reset the per-game variables
      frame();  // start the first frame
    }
    function showStats() {
      stats.domElement.id = 'stats';
      get('menu').appendChild(stats.domElement);
    }
    function addEvents() {
      document.addEventListener('keydown', keydown, false);
      window.addEventListener('resize', resize, false);
    }
    function resize(event) {
      canvas.width   = canvas.clientWidth;  // set canvas logical size equal to its physical size
      canvas.height  = canvas.clientHeight; // (ditto)
      ucanvas.width  = ucanvas.clientWidth;
      ucanvas.height = ucanvas.clientHeight;
      dx = canvas.width  / nx; // pixel size of a single tetris block
      dy = canvas.height / ny; // (ditto)
      invalidate();
      invalidateNext();
    }
    function keydown(ev) {
      var handled = false;
      if (playing) {
        switch(ev.keyCode) {
          case KEY.LEFT:   actions.push(DIR.LEFT);  handled = true; break;
          case KEY.RIGHT:  actions.push(DIR.RIGHT); handled = true; break;
          case KEY.UP:     actions.push(DIR.UP);    handled = true; break;
          case KEY.DOWN:   actions.push(DIR.DOWN);  handled = true; break;
          case KEY.ESC:    lose();                  handled = true; break;
        }
      }
      else if (ev.keyCode == KEY.SPACE) {
        play();
        handled = true;
      }
      if (handled)
        ev.preventDefault(); // prevent arrow keys from scrolling the page (supported in IE9+ and all other browsers)
    }
    //-------------------------------------------------------------------------
    // GAME LOGIC
    //-------------------------------------------------------------------------
    function play() { hide('start'); reset();          playing = true;  }
    function lose() { show('start'); setVisualScore(); playing = false; }
    function setVisualScore(n)      { vscore = n || score; invalidateScore(); }
    function setScore(n)            { score = n; setVisualScore(n);  }
    function addScore(n)            { score = score + n;   }
    function clearScore()           { setScore(0); }
    function clearRows()            { setRows(0); }
    function setRows(n)             { rows = n; step = Math.max(speed.min, speed.start - (speed.decrement*rows)); invalidateRows(); }
    function addRows(n)             { setRows(rows + n); }
    function getBlock(x,y)          { return (blocks && blocks[x] ? blocks[x][y] : null); }
    function setBlock(x,y,type)     { blocks[x] = blocks[x] || []; blocks[x][y] = type; invalidate(); }
    function clearBlocks()          { blocks = []; invalidate(); }
    function clearActions()         { actions = []; }
    function setCurrentPiece(piece) { current = piece || randomPiece(); invalidate();     }
    function setNextPiece(piece)    { next    = piece || randomPiece(); invalidateNext(); }
    function reset() {
      dt = 0;
      clearActions();
      clearBlocks();
      clearRows();
      clearScore();
      setCurrentPiece(next);
      setNextPiece();
    }
    function update(idt) {
      if (playing) {
        if (vscore < score)
          setVisualScore(vscore + 1);
        handle(actions.shift());
        dt = dt + idt;
        if (dt > step) {
          dt = dt - step;
          drop();
        }
      }
    }
    function handle(action) {
      switch(action) {
        case DIR.LEFT:  move(DIR.LEFT);  break;
        case DIR.RIGHT: move(DIR.RIGHT); break;
        case DIR.UP:    rotate();        break;
        case DIR.DOWN:  drop();          break;
      }
    }
    function move(dir) {
      var x = current.x, y = current.y;
      switch(dir) {
        case DIR.RIGHT: x = x + 1; break;
        case DIR.LEFT:  x = x - 1; break;
        case DIR.DOWN:  y = y + 1; break;
      }
      if (unoccupied(current.type, x, y, current.dir)) {
        current.x = x;
        current.y = y;
        invalidate();
        return true;
      }
      else {
        return false;
      }
    }
    function rotate() {
      var newdir = (current.dir == DIR.MAX ? DIR.MIN : current.dir + 1);
      if (unoccupied(current.type, current.x, current.y, newdir)) {
        current.dir = newdir;
        invalidate();
      }
    }
    function drop() {
      if (!move(DIR.DOWN)) {
        addScore(10);
        dropPiece();
        removeLines();
        setCurrentPiece(next);
        setNextPiece(randomPiece());
        clearActions();
        if (occupied(current.type, current.x, current.y, current.dir)) {
          lose();
        }
      }
    }
    function dropPiece() {
      eachblock(current.type, current.x, current.y, current.dir, function(x, y) {
        setBlock(x, y, current.type);
      });
    }
    function removeLines() {
      var x, y, complete, n = 0;
      for(y = ny ; y > 0 ; --y) {
        complete = true;
        for(x = 0 ; x < nx ; ++x) {
          if (!getBlock(x, y))
            complete = false;
        }
        if (complete) {
          removeLine(y);
          y = y + 1; // recheck same line
          n++;
        }
      }
      if (n > 0) {
        addRows(n);
        addScore(100*Math.pow(2,n-1)); // 1: 100, 2: 200, 3: 400, 4: 800
      }
    }
    function removeLine(n) {
      var x, y;
      for(y = n ; y >= 0 ; --y) {
        for(x = 0 ; x < nx ; ++x)
          setBlock(x, y, (y == 0) ? null : getBlock(x, y-1));
      }
    }
    //-------------------------------------------------------------------------
    // RENDERING
    //-------------------------------------------------------------------------
    var invalid = {};
    function invalidate()         { invalid.court  = true; }
    function invalidateNext()     { invalid.next   = true; }
    function invalidateScore()    { invalid.score  = true; }
    function invalidateRows()     { invalid.rows   = true; }
    function draw() {
      ctx.save();
      ctx.lineWidth = 1;
      ctx.translate(0.5, 0.5); // for crisp 1px black lines
      drawCourt();
      drawNext();
      drawScore();
      drawRows();
      ctx.restore();
    }
    function drawCourt() {
      if (invalid.court) {
        ctx.clearRect(0, 0, canvas.width, canvas.height);
        if (playing)
          drawPiece(ctx, current.type, current.x, current.y, current.dir);
        var x, y, block;
        for(y = 0 ; y < ny ; y++) {
          for (x = 0 ; x < nx ; x++) {
            if (block = getBlock(x,y))
              drawBlock(ctx, x, y, block.color);
          }
        }
        ctx.strokeRect(0, 0, nx*dx - 1, ny*dy - 1); // court boundary
        invalid.court = false;
      }
    }
    function drawNext() {
      if (invalid.next) {
        var padding = (nu - next.type.size) / 2; // half-arsed attempt at centering next piece display
        uctx.save();
        uctx.translate(0.5, 0.5);
        uctx.clearRect(0, 0, nu*dx, nu*dy);
        drawPiece(uctx, next.type, padding, padding, next.dir);
        uctx.strokeStyle = 'black';
        uctx.strokeRect(0, 0, nu*dx - 1, nu*dy - 1);
        uctx.restore();
        invalid.next = false;
      }
    }
    function drawScore() {
      if (invalid.score) {
        html('score', ("00000" + Math.floor(vscore)).slice(-5));
        invalid.score = false;
      }
    }
    function drawRows() {
      if (invalid.rows) {
        html('rows', rows);
        invalid.rows = false;
      }
    }
    function drawPiece(ctx, type, x, y, dir) {
      eachblock(type, x, y, dir, function(x, y) {
        drawBlock(ctx, x, y, type.color);
      });
    }
    function drawBlock(ctx, x, y, color) {
      ctx.fillStyle = color;
      ctx.fillRect(x*dx, y*dy, dx, dy);
      ctx.strokeRect(x*dx, y*dy, dx, dy)
    }
    //-------------------------------------------------------------------------
    // FINALLY, lets run the game
    //-------------------------------------------------------------------------
    run();
  </script>