Diamond Reaction: An HTML5 Chain Reaction Game using Crafty JS

I've been away from blogging for a long time. Maybe because I've not been learning code-detailed topics. I've been more like learning the basics in topics I've never tries before (like PHP) and learning some theoretical topics.

Anyways, this time I'm trying a new approach to gain more experience. This was I can gain experience from anything I want to learn. So here is my almost-full game implementation of an HTML5 chain reaction game called: Diamond Reaction.

Play Diamond Reaction now

Let's talk a bit about it:

Idea:
I wanted to make a game for fun, with the focus on game mechanics. So I started thinking of some ideas that can be fun for a 'mario-lover' like me. Whenever I think of an idea, I search about it and see how frequent I find the same mechanics on the web. Till I arrived at this concept that did not have a big hit before: chain reaction games.

Theme:
If you look at a game like Angry Birds, you can find the game mechanics are not that hard or new. But the theme is what made it a big hit. I'm doing my game for fun and experience and I'm not a graphic designer, so I started searching for the common simple themes for the popular games these days, especially on Facebook. The most noticed theme was the cartoonish diamonds theme (plus bubbles and animals). So I picked this theme because It will not need much effort to make, plus it actually makes the game more fun to play (you can search for chain reaction games and see how boring their graphics are).

Implementation:
Since the concept of chain reaction game is not that hard to implement, and I already know how to use Crafty JS framework, the game did not take much time to get to the first demo.

Gamification:
I thought about adding a small feature to add more fun and challenge to the game: highscore and leaderoard. but I did not to keep user data on my small server. So I decided to add an optional Facebook login button to login with Facebook credentials so that I can use the Scores API the Facebook has.

Balance:
These kinds of small games can get boring if I did not find the right balance for the game. Since it was a very small game with no big details, fine-tuning was made easily by playing and -trial-and-error.

Missing features:
- No sound was added, maybe I can add it later.
- I'm not satisfied with the current balancing.
- Add more items and surprises to the game to make it more fun and engaging.

Play Diamond Reaction now

Full HTML5 Game Example with Crafty JS

A couple of days ago, I participated in a game jam called "Game Zanga". It was a three-day contest for game development with some conditions: in Arabic, related to a topic announced at the start of the three days (it was "Freedom"), and browser-based.

So it was a nice chance to test my knowledge and experience in game development (which is a new thing to me) and I decided to use Crafty (or maybe some call it CraftyJS). Crafty is a JavaScript game library using HTML5. One great power in Crafty is that it can use Canvas or DOM. Plus the concept of Components and Entities that allow you to develop the game in a OO style.

So, I thought I can post my code for anyone to learn from. Although it is not perfect code and it neads more refactoring and fine-tuning, it is still a good example of how a game can look like in Crafty. I almost did not need anything other than the API documentation on Crafty website (plus the tutorial if you are to start from the very beginning). So with decollapsing the code you'll immediately have a general overview of how the game code looks like, then collapsing the code can do the job to get to the details.

One important note, this game was intended to be an Arabic game, so here are some guidelines:
- The first icon in the home screen is the "Start" button.
- Once the game starts, you have two blue cannons on the left. Click any of them to use it.
- Your abjective is to let the blue soldiers pass ("unrwa" in code) and kill the green ones ("soldier" in code).
- Life points decrease if any green soldier passes.
- Your weapon is upgraded while playing.


Finally, you'll notice some faults in collision detection and a lot of other things in the code, but remember that it was made in only two days by me (a newbie) using Crafty which lacks the variety of full examples to learn from. Anyways, you'll get the idea of a full game in less than 1000 lines and then you can make your own best seller.

Here are some screenshots, followed by a download link.

Download game code here.

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