main.js

// array of all the levels in our game
var levels = [ new Level() ];

// the current level index into our levels array
var currentLevel = 0;

// basic camera object
var camera = { x: 0, y: 0 };

// handle keyboard controls
var keysDown = { };
addEventListener(
    "keydown", 
    function (e) { 
        for (var k in Keys) {
            if (Keys[k] == e.keyCode) {
                keysDown[e.keyCode] = true; 
                if (e.preventDefault) { e.preventDefault(); } 
                return true; 
            }
        }
    }, 
    false);
addEventListener(
    "keyup", 
    function (e) { 
        for (var k in Keys) {
            if (Keys[k] == e.keyCode) {
                delete keysDown[e.keyCode]; 
                if (e.preventDefault) { e.preventDefault(); } 
                return true; 
            }
        }
    }, 
    false);

// the visibility type
var visibilityType = 'room';

// flag for taking screenshots
var takeScreenshot = false;

// ensure we have requestAnimationFrame available for us
if (!window.requestAnimationFrame) {
    window.requestAnimationFrame = (function() {
        return window.requestAnimationFrame ||
               window.webkitRequestAnimationFrame ||
               window.mozRequestAnimationFrame ||
               window.oRequestAnimationFrame ||
               window.msRequestAnimationFrame ||
               function(callback, element) { window.setTimeout(callback, 1000/60); };
    })();
}

function ResetGame() {
    levels = [ new Level() ];
    currentLevel = 0;
    camera = { x: 0, y: 0 };
    keysDown = { };
}

function Screenshot() { 
    takeScreenshot = true; 
}

function Update(elapsed) {  
    // update the level
    var change = levels[currentLevel].update(elapsed, keysDown);
    
    // handle moving up and down floors
    if (change == -1) {
        if (currentLevel > 0) {
            currentLevel--;
        }
    }
    else if (change == 1) {
        // make sure we create new levels as we go down if we're at the end of the array
        if (currentLevel == levels.length - 1) {
            levels.push(new Level());
        }
        
        currentLevel++;
    }
    
    // compute the camera position using the player's center
    var canvas = document.getElementById('myCanvas');
    var player = levels[currentLevel].player;
    var cx = player.pos.x + player.size.x / 2;
    var cy = player.pos.y + player.size.y / 2;
    camera.x = Math.floor(cx - canvas.width / 2);
    camera.y = Math.floor(cy - canvas.height / 2);
}

function Draw() {        
    // get the canvas
    var canvas = document.getElementById('myCanvas');
    
    // grab the context and draw the background color
    var context = canvas.getContext('2d');        
    context.fillStyle = 'black';
    context.fillRect(0, 0, canvas.width, canvas.height);
    
    // draw the current level
    levels[currentLevel].draw(canvas, context, camera, visibilityType);
    
    if (takeScreenshot) {
        // get the Data URL from the canvas and open it in a new window
        window.open(document.getElementById('myCanvas').toDataURL('image/png'));
        takeScreenshot = false;
    }
}

var prevTime = Date.now();
function MainLoop() {
    // request an update for the next frame
    window.requestAnimationFrame(MainLoop, document.getElementById('myCanvas'));

    // compute our elapsed time
    var time = Date.now();
    var delta = (time - prevTime) / 1000.0;
    prevTime = time;

    // update the game
    Update(delta);

    // draw the game
    Draw();
}

function Initialize() {
    // hook the visibility chooser's event so we can update the level
    var visibility = document.getElementById('visibility');
    visibility.onchange = function() {visibilityType = visibility.options[visibility.selectedIndex].value;}

    // start our loop
    window.requestAnimationFrame(MainLoop, document.getElementById('myCanvas'));
}