JS1k: The JavaScript code golfing competition

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eval(d)

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//
// columns.js
//
// js1k contest entry
//
// Copyright (c) 2010 Patrick Walton
//

var PLAYFIELD_WIDTH = 6;
var PLAYFIELD_HEIGHT = 12;
var GEM_SIZE = 24;
var GEM_RADIUS = 12;
var CANVAS_WIDTH = 144;
var CANVAS_HEIGHT = 288;

var COLORS = [ "red", "#f80", "#ff0", "#0f0", "#00f", "#808" ];

var canvas = document.getElementById("c");
canvas.width = CANVAS_WIDTH;
canvas.height = CANVAS_HEIGHT;

var ctx = canvas.getContext('2d');

var playfield = {};

var fallingColumn;
var fallingColumnR, fallingColumnC;

var score = 0, bonus;

function rand(n) {
    return (Math.random() * n) >> 0;
}

function sendNewColumn() {
    if (playfield["0,3"])
        playfield = {}, score = 0;

    fallingColumnR = 0;
    fallingColumnC = 3;
    fallingColumn = [];
    for (var i = 0; i < 3; i++)
        fallingColumn[i] = COLORS[rand(6)];
}

function drawGemAt(r, c, color) {
    ctx.beginPath();
    ctx.fillStyle = color;
    ctx.arc(GEM_RADIUS + c * GEM_SIZE, GEM_RADIUS + r * GEM_SIZE, GEM_RADIUS,
        0, 7, !1);
    ctx.fill();
}

function render() {
    // Erase the playfield.
    canvas.width++;
    canvas.width--;

    ctx.fillStyle = "#000";
    ctx.fillText(score, 0, 9);

    for (var pos in playfield) {
        var pt = pos.split(",");
        var color = playfield[pos];
        if (color)
            drawGemAt(pt[0], pt[1], color);
    }

    for (var i = 0; i < 3; i++)
        drawGemAt(fallingColumnR - i, fallingColumnC, fallingColumn[i]);
}

function fallingPieceCollidesWithPlayfieldAt(r, c) {
    return (r >= PLAYFIELD_HEIGHT || c < 0 || c >= PLAYFIELD_WIDTH ||
        playfield[r + "," + c] || playfield[(r-1) + "," + c] ||
        playfield[(r-2) + "," + c]);
}

// Carry out the effects of gravity!
function fall() {
    for (var c = 0; c < PLAYFIELD_WIDTH; c++) {
        for (var r = 0; r < PLAYFIELD_HEIGHT - 1; r++) {
            var pos = r + "," + c;
            var nextPos = (r+1) + "," + c;
            if (playfield[pos] && !playfield[nextPos]) {
                playfield[nextPos] = playfield[pos];
                playfield[pos] = 0;
                r = 0;
            }
        }
    }
}

function checkForMatches() {
    var i = 0, marked = [];

    function check(roffset, coffset) {
        var pos1;
        for (pos1 in playfield) {
            var color1 = playfield[pos1];
            if (color1) {
                var pt = pos1.split(",");
                var r = +pt[0], c = +pt[1];
                r += roffset, c += coffset;
                var pos2 = r + "," + c;
                r += roffset, c += coffset;
                var pos3 = r + "," + c;
                if (color1 == playfield[pos2] && color1 == playfield[pos3])
                    marked.push(pos1, pos2, pos3);
            }
        }
    }

    check(1, 0);    // - horizontal
    check(0, 1);    // | vertical
    check(1, 1);    // \ diagonal
    check(1, -1);   // / diagonal

    while (marked[i]) {
        score += bonus *= 2;
        playfield[marked[i++]] = 0;
    }

    return marked[0];
}

function tick() {
    if (fallingPieceCollidesWithPlayfieldAt(++fallingColumnR,
            fallingColumnC)) {
        // Anchor the falling column in place.
        // TODO: check for game over
        var r = fallingColumnR, c = fallingColumnC;
        var gem;
        while ((gem = fallingColumn.shift()))
            playfield[--r + "," + c] = gem;
        bonus = 5;
        while (checkForMatches())
            fall();
        sendNewColumn();
    }

    render();
}

function onKeyDown(ev) {
    var code = ev.which - 38;
    var newC = fallingColumnC + code;
    ((code == -1 || code == 1) &&
        !fallingPieceCollidesWithPlayfieldAt(fallingColumnR, newC) &&
        (fallingColumnC = newC)) ||
        (!code && fallingColumn.unshift(fallingColumn.pop()));
    render();
}

setInterval(tick, 500);
document.onkeydown = onKeyDown;

sendNewColumn();
render();