Game development

This astronaut just wants a friend! A Ludum Dare Post-mortem

Another Ludum Dare came and went and I managed to (mostly) complete a little HTML5 minigame. I didn’t really hit crunch time until the last few hours of the jam, and wasted far too much time during the compo not programming.  I’ve gotten to the point that I’m pretty comfortable with Phaser.js, and am able to spend more time figuring out game mechanics.

In ‘With Kindness’, you play a lonely astronaut, stranded on a far away planet. All he wants is to make some new friends. There are many aliens on the planet, that constantly spit acid at you, but maybe, just maybe, if you give them a good hug they will become your friend!

With Kindness Screenshot

I was initially uninspired by the theme, ‘An Unconventional Weapon’, but managed to come up with a decent idea. Though, while rating other games during the judging phase I came across a few other games also using hugging as a weapon.

I’ve been wanting to play around with making some kind of a beat-em-up style game, and used this Ludum Dare to explore and learn some of the challenges I’d run into. Probably the most difficult involved splitting one sprite into multiple sprites in order to layer them, and provide better collision detection.

With Kindness Sprites
A small selection of sprites from With Kindness

I attempted to keep the astronaut and the alien sprites separate, so I’d be able to separate both their animation, but ultimately ended up having to attach the alien to the astronaut sprite when they’re hugging. Time is always the enemy during Ludum Dare and I spent most of the time creating the astronaut sprite frames and trying to figure out how to position and layer them correctly.

I used the gulp config to build a texture atlas I’ve written about previously, which saved a massive amount of time (at least it felt like it) compared to having to manually create and update the atlas.

I only wish I’d saved some time to add some sound effects and music.  I think a super happy pop melody would really complete the experience, but I don’t see much of a future beyond that for the game.

Check out the Ludum Dare entry or Play the game directly. Feel free to check out the With Kindness Source Code, but as is standard for a 48 hour game jam, things got a little sloppy towards the end.

And since I forgot in-game instructions:

WASD or Arrow keys to move around, F key to initiate hug, continue pressing F to hug even harder!

Exploding sprites with Phaser.js and Shatter.js

I’ve been working on increasing Crash Landing‘s juiciness and one of my first tasks was to make the ground beneath the player explode into pieces. It’s been a great opportunity to  get some use out of Shatter.js.

It wasn’t completely straightforward to figure out how to access the raw image data in order to feed it to Shatter.js, and how to best provide the shattered image back to Phaser. Since I’m loading the sprites from a sprite atlas I need to extract the individual sprite I want to shatter to it’s own image. I could also just load the images individually, but I really wanted to keep the sprite atlas and not load duplicate images.

Next I created a sprite group to contain all the shattered pieces, with each shattered piece placed in it’s correct spot so that when the group is rendered it still visually appears as one object. Then we can interact with the group as a whole and also each sprite individually. To make them explode I just loop through all of them and a random x and y velocity.

Most of the magic is all in ShatterSprite.js which I’ve heavily commented below:


CrashLanding.Util.ShatterSprite = function ShatterSprite(game, key, frame) {
    var numberOfSprites = 12; // make 12 sprites from frame
    var offCanvas = -1000; // constant to create sprites outside of game canvas

    function getImageFromSprite(game, key, frame) {
       // temp sprite used for extraction
       var sprite = game.add.sprite(offCanvas, offCanvas, key, frame);
       // create a canvas to draw the sprite to with Phaser's bitmapData method
       var bmd = game.add.bitmapData(sprite.width, sprite.height);
       // create an image and set the image data, and clean up
       var image = new Image();
       bmd.draw(sprite, 0, 0, sprite.width, sprite.height);
       bmd.update();
       sprite.destroy();
       image.src = bmd.canvas.toDataURL();
       return image;
    }
    
    // Create a phaser group out of a Shatter object
    function createShatteredGroup(game, shatteredImage) {
       var shatteredGroup = game.add.group();
       // Shatter.js returns the new images in an array at Shatter.images, here we loop through all of them
       shatteredImage.images.forEach(function(image, ind, arr) {
          // create a key for the using the same name as the frame of the original sprite + its position in the array of shattered images
          var key = frame + ind;
          // add it to the game cache, so we can add it to the new sprite group
          game.cache.addImage(key, null, image.image);
          var sprite = shatteredGroup.create(offCanvas, offCanvas, key);
          // save the sprites offset so we can place it properly when drawing the groupp
          sprite.originX = image.x;
          sprite.originY = image.y;
          game.physics.arcade.enable(sprite);
          // for the shattered ground objects I only check down collision. Need to move this out and pass in.
          sprite.body.checkCollision.left = false;
          sprite.body.checkCollision.right = false;
          sprite.body.checkCollision.up = false;
       });
       return shatteredGroup;
    }

    return createShatteredGroup(game,
       new Shatter(getImageFromSprite(game, key, frame), numberOfSprites));
}

Once I’ve created my sprite group I can use it to replace sprites/tiles on the screen.  The ground exploding awesomeness takes place in the appropriately named Ground.js. Below, ‘exploder’ is the shattered sprite group and oldTile is the tile I’ve decided to remove from the game world.


oldTile = game.level1map.removeTileWorldXY(removeX, groundLevel, tileWidth, tileHeight);
       // I'm randomly removing tiles, so I make sure there was a tile removed
       if (typeof oldTile != 'undefined') {
          // set shattered group to the previous location of the tile
          exploder.x = oldTile.worldX;
          exploder.y = oldTile.worldY;
          // add each piece at it's proper location within the group and give it some velocity
          exploder.children.forEach(function(sprite) {
             sprite.x = sprite.originX;
             sprite.y = sprite.originY;
             sprite.body.velocity.x = game.rnd.integerInRange(xVelocityMin, xVelocityMax);
             sprite.body.velocity.y = game.rnd.integerInRange(yVelocityMin, yVelocityMax);
          });

There are plenty of improvements we could make, but I think this provides a decent example of how to use Shatter.js with Phaser.js.

Using gulp to automate texture atlas and sprite sheet creation for Phaser

I’ve always used TexturePacker to create texture atlases for Phaser. It’s an awesome visual tool that’s really easy to use to create atlases and sprite sheets, but I’m a command line guy and always looking to save time and be more efficient.

While I’ve been working on Crash Landing, I hesitate to update or add new sprites because of the pain of having to go through all the steps to update or add a sprite. It may sound a bit silly, but it really is time consuming having to open up the program, load the old atlas, add or update it and save it back out. I’d rather spend this time coding, or creating new sprites. My dislike for this process makes me not want to create new sprites and iterate quickly.

I first looked into automating TexturePacker, which does have a command line interface, but at the same time being a standalone program I’d have to write a bash script to automate the process, or find a gulp package to interact with the command line (seems a little messy). I plan on building a full workflow for automating more tasks using Gulp, so I did a little research and found a working implementation using existing Node.js packages.

gulp.spritesmith and spritesmith-texturepacker

gulp.spritesmith is a gulp plugin for spritesmith, a node utility to create spritesheets, and spritesmith-texturepacker is an export template for spritesmith to create a .json file compatible with TexturePacker, and thus Phaser.

So let’s get to it. If you’re familiar with gulp already it’s pretty simple to set up. I’m assuming you’ve got npm and are familiar with installing packages. You’ll need gulp in your project, both spritesmith packages above, and I’m also using imagemin to optimize the resulting atlas image file.


npm install --save-dev gulp gulp-spritesmith spritesmith-texturepacker gulp-imagemin

Once installed we just need to create our gulp file with a task to create the texture atlas image and json file.


var gulp = require('gulp');
var spritesmith = require('gulp.spritesmith');
var imagemin = require('gulp-imagemin');
var texturepacker = require('spritesmith-texturepacker');

gulp.task('sprites', function() {
    var spriteData = gulp.src('src/images/sprites/*.png')
        .pipe(spritesmith({
            imgName: 'sprites.png',
            cssName: 'sprites.json',
            algorithm: 'binary-tree',
            cssTemplate: texturepacker
    }));
    spriteData.img.pipe(imagemin()).pipe(gulp.dest('build/images/'));
    spriteData.css.pipe(gulp.dest('build/images'));
});

I’ve created a task (sprites) that pulls all .png files from the src directory, pipes it into spritesmith with the texturepacker template. I save the return value of the operation to spriteData, and individually pipe them out so I can run the image through imagemin.

Now anytime I need to add or update a sprite, I just drop it into the source file and run ‘gulp sprites’.

The .json file outputted will be in JSON hash format. In order to load the spritesheet into a Phaser project you’ll use the atlasJSONHash method. I’m using this:


this.load.atlasJSONHash('sprites', 'build/images/sprites.png', 'build/images/sprites.json');

Each image is saved as a frame in the .json file. You’ll refer to it by the filename minus the extension. As an example, I’m loading the standing.png frame into my player class with the following:


Phaser.Sprite.call(this, game, x, y, 'sprites', 'standing');

So there it is, a simple way to speed up your workflow. Works great if you like to incrementally build out you’re Phaser game like I do.

Ludum Dare 28 – Make a game in 48 hours

Ludum Dare is an event where people all around the world attempt to make a game in 48 hours, based on a theme voted on and announced at the start of the competition. There are no prizes, it’s more of a challenge to generate ideas and get people to make games.

I’ve wanted to participate in Ludum Dare for a couple years now and it just happened to fall on a completely free weekend for me this time, so I made my first HTML5 game.

Well, I consider it a prototype at this point. I used an HTML5 framework called Phaser, which I’ve had my eye on for awhile but haven’t worked with before. I spent a ton of time learning the framework through the excellent documentation and examples on the Phaser website.

I feel it was a success as now I have a working game prototype, instead of just a vague idea in my head. There is plenty of work to do but I feel it was definitely a worthwhile way to blow a weekend.

Check out my entry on the Ludum Dare website here:

http://www.ludumdare.com/compo/ludum-dare-28/?action=preview&uid=15070

 

P.S. – I’m running off about 10 hours of sleep over the weekend, please excuse the rambling nature of this post.