My HTML5 Canvas Profile Widget

Since I've not been innovating much outside work for a while now, I thought I could make any new "thing" to aggregate a few benefits I've been aiming for. The output was this HTML5 canvas, game-like, Egytian-themed profile widget. It was a chance to play with HTML5 canvas, and still stick to the design of the game loop. It was also a chance to change the look of my boring blogs.

You play the game. Drop the egg from the profile you want to visit. If the egg hits the nest, you earn the visit to the profile.

So without any more talking, the code is pretty simple:

• A game loop
• Check for user input (mouse clicks)
• Update the values of some objects
• Detect collisions of some objects and acting accordingly
• Draw objects

Notes:

• The javaScript code is hosted online and only referenced to in my HTML code. This was better to update the code once and apply it to all the places where I use it. (as a desktop/mobile developer, this is great).
• Loading an image at runtime made a lag of maybe one second when a egg is dropped, but it looked ugly so I commented the code regarding loading the egg images in runtime and used a single preloaded image instead.
• I've looked about three times for performance boosters. But still this does not mean this is the best to get from HTML5 canvas and Javascript. It is just about the amount of time I gave to this code.
• If I did not put much comments, it was because I thought the code is self-explaining.

I preferred to post the code here again for better syntax highlighting
[profile_widget_script.js]

var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');

var globalFPS               = 20;
var maxItemSpeed            = 2;
var eggSpeed                = 8;
var eggSize                 = 32;
var minItemHeight           = 200;
var iconSize                = 32;
var wingSize                = 32;
var nestX                   = 100;
var nestY                   = 330;
var nestMaxX                = 150;
var nestMinX                = 50;
var nestWidth               = 96;
var nestHeight              = 57;
var nestSpeed               = 2;
var mouseEventFlag          = false;
var mouseEventX             = 0;
var mouseEventY             = 0;
var wave1X                  = -10;
var wave1Y                  = 360;
var wave1Direction          = 1;
var wave2X                  = -25;
var wave2Y                  = 375;
var wave2Direction          = 1;
var wave3X                  = -40;
var wave3Y                  = 390;
var wave3Direction          = 1;
var waveXThreshold          = -50; // where to toggle the direction of wave
var waveSpeed               = 2;

// put the items you want to show here {icon to fly, redirecting url, egg to drop}
var profilesArray = [
            {
            icon:   "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/facebook_32x32.png",
            url:    "http://www.facebook.com/MahmoudAdly",
            egg:    "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/egg.png"
            },
            {
            icon:   "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/twitter_32x32.png",
            url:    "http://www.twitter.com/MahmoudAdly",
            egg:    "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/egg.png"
            },
            {
            icon:   "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/gplus_32x32.png",
            url:    "https://plus.google.com/103333225222170744758",
            egg:    "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/egg.png"
            },
            {
            icon:   "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/goodreads_32x32.png",
            url:    "http://www.goodreads.com/MahmoudAdly",
            egg:    "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/egg.png"
            },
            {
            icon:   "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/linkedin_32x32.png",
            url:    "http://www.linkedin.com/in/MahmoudAdly",
            egg:    "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/egg.png"
            },
            {
            icon:   "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/blogger0_32x32.png",
            url:    "http://3adly.blogspot.com/",
            egg:    "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/egg.png"
            },
            {
            icon:   "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/blogger1_32x32.png",
            url:    "http://free-3adly.blogspot.com/",
            egg:    "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/egg.png"
            }
            ];
            
var items = [];
var eggs = [];
var wingImage = new Image;
var nestImage = new Image();
var background = new Image();
var waveImage1 = new Image();
var waveImage2 = new Image();
var waveImage3 = new Image();
var eggImage = new Image(); // loading one egg to use it later, for performance reasons

wingImage.src = "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/wing_32x32.png";
nestImage.src = "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/nest.png";
background.src = "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/background.png";
waveImage1.src = "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/wave_1.png";
waveImage2.src = "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/wave_2.png";
waveImage3.src = "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/wave_3.png";
eggImage.src = "http://dl.dropbox.com/u/44163256/html5-profile-widget/assets/egg.png";

var nest = {
    image: nestImage,
    x: nestX,
    y: nestY,
    width: nestWidth,
    height: nestHeight,
    speed: nestSpeed,
    xDirection: 1,
    minX: nestMinX,
    maxX: nestMaxX
};

createItems();
setInterval(gameLoop, 1000/globalFPS);

function gameLoop(){
    updateUserInput();
    updateItems();
    updateEggs();
    updateNest();
    updateWaves();
    checkEggsCollision();
    drawBackground();
    drawWaves()
    drawItems();
    drawNest();
    drawEggs();
}

function createItems() {
    for(var i in profilesArray) {
        var profile = profilesArray[i];
        var img = new Image();
        img.src = profile.icon;
        
        items.push({
                x: 0- Math.random()*500, // so icons do not appear at once
                y: Math.random()*minItemHeight,
                speed: 1+Math.random()*maxItemSpeed,
                image: img,
                url: profile.url,
                egg: profile.egg,
                wingRotation: 0,
                wingRotationDirection: 1
        });
    }
}

function updateItems() {
    for(var i in items) {
        var item = items[i];
        item.x += item.speed;
        item.wingRotation += item.wingRotationDirection * 0.1
        if(item.wingRotation > Math.PI/4)
        {
            item.wingRotationDirection = -1;
        }
        else if(item.wingRotation < 0)
        {
            item.wingRotationDirection = 1;
        }
        
        // if item gets out of canvas scope
        if(item.x > canvas.width) {
            // recycle the item and set different values instead of removing it
            item.x = 0-Math.random()*100;
            item.y = Math.random()*minItemHeight;
            item.speed = 1+Math.random()*maxItemSpeed //between 2 and 5
            item.wingRotation = 0;
        }
    }
}

function updateEggs(){
    for(var i in eggs){
        var egg = eggs[i];
        egg.y += egg.speed;
        
        // if egg gets out of canvas scope
        if(egg.x > canvas.height) {
                // remove egg from array
                eggs.splice(i, 1);
        }
    }
}

function updateNest(){
    nest.x += nest.xDirection * nest.speed;
    
    if(nest.x > nest.maxX){
        nest.xDirection = -1;
    }
    else if(nest.x < nest.minX){
        nest.xDirection = 1;
    }
}

function updateWaves(){
    wave1X += wave1Direction*waveSpeed;
    if(wave1X > 0)
        wave1Direction = -1;
    else if(wave1X < waveXThreshold)
        wave1Direction = 1;
        
    
    wave2X += wave2Direction*waveSpeed;
    if(wave2X > 0)
        wave2Direction = -1;
    else if(wave2X < waveXThreshold)
        wave2Direction = 1;
    
    wave3X += wave3Direction*waveSpeed;
    if(wave3X > 0)
        wave3Direction = -1;
    else if(wave3X < waveXThreshold)
        wave3Direction = 1;
    
}

function checkEggsCollision(){
    for(var i in eggs){
        var egg = eggs[i];
        if(egg.x+eggSize > nest.x+nest.width/3
            && egg.x < nest.x+2*nest.width/3
            && egg.y+eggSize > nest.y+nest.height/3
            && egg.y < nest.y+2*nest.height/3)
            {
                alert("Thanks for trying my profile widget. You will now be redirected to: \n"
                        + egg.url);
                location.href = egg.url;
                // remove egg from array
                eggs.splice(i, 1);
            }
    }
}

function updateUserInput() {
    if(!mouseEventFlag)
        return;
    
    for(var i in items)
    {
        var item = items[i];
        if( item.x < mouseEventX 
            && mouseEventX < item.x + iconSize
            && item.y < mouseEventY
            && mouseEventY< item.y  + iconSize)
            {
                /* instead of loading the egg in runtime, load it once (eggImage) at startup and use it.
                    Because for a web view, it takes a second to load the image, which looks bad.*/
                //var img = new Image();
                //img.src = item.egg;
                
                eggs.push({
                    x: item.x,
                    y: item.y + iconSize,
                    speed: eggSpeed,
                    image: eggImage,
                    url: item.url
                    });
                mouseEventFlag = false;
                return;
            }
    }
}

function drawBackground() {
    context.drawImage(background, 0, 0);
}

function drawWaves(){
    context.drawImage(waveImage1, wave1X, wave1Y);
    context.drawImage(waveImage2, wave2X, wave2Y);
    context.drawImage(waveImage3, wave3X, wave3Y);
}

function drawItems() {
    for(var i in items) {
        var item = items[i];
        context.drawImage(item.image, item.x, item.y);
        context.save();
        context.translate(item.x+10, item.y+10);
        context.rotate(-item.wingRotation);
        context.drawImage(wingImage, -wingSize, -wingSize);
        context.restore();
    }
}

function drawNest(){
    context.drawImage(nest.image, nest.x, nest.y);
}

function drawEggs() {
    for(var i in eggs) {
        var egg = eggs[i];
        context.drawImage(egg.image, egg.x, egg.y);
    }
}

canvas.onmousedown = function(e) {
    var mousePos = getMousePos(canvas, e);
    mouseEventX = mousePos.x;// - currentTranslationX;
    mouseEventY = mousePos.y;// - currentTranslationY;
    mouseEventFlag = true;
};

canvas.onmouseup = function(e) {
    mouseEventFlag = false;
};

function getMousePos(canvas, evt){
    // get canvas position
    var obj = canvas;
    var top = 0;
    var left = 0;
    while (obj && obj.tagName != 'BODY') {
        top += obj.offsetTop;
        left += obj.offsetLeft;
        obj = obj.offsetParent;
    }
 
    // return relative mouse position
    var mouseX = evt.clientX - left + window.pageXOffset;
    var mouseY = evt.clientY - top + window.pageYOffset;
    return {
        x: mouseX,
        y: mouseY
    };
}

Resources:
HTML5 Canvas Deep Dive
HTML5 Canvas Mouse Coordinates Tutorial