Tuesday, April 01, 2014

Creating your first HTML5 spaceship game for the Android* OS on Intel(R) Architecture

I'm certain most of us have some insane or not so insane video game plans in mind. The majority of these thoughts are never acted on as many people think game coding is exceptionally hard to do. Indeed that is true to a degree, but it is not as hard as you may think.

If you have a fundamental understanding of HTML, CSS, and JavaScript*, you have all the requisites to start a straightforward project.

Adding a Canvas element to a web page

One of the most exciting features of HTML5 is the <canvas> element that can be used to draw vector graphics and engender astonishing effects, interactive games, and animations The web defines canvas, as a rectangular area that allows for dynamic, scriptable rendering of 2D shapes and bitmap images. The HTML5 Canvas is perfect for creating great visual results that augment UIs, diagrams, photo albums, charts, graphs, animations, and embedded drawing applications. HTML5 Canvas works with JavaScript libraries and CSS3 enabling you to create interactive web-based games and animations.

The elementary code for using and setting a canvas looks like this:

<body onload="spaceShipGame()">
    <canvas id="spaceCanvas" width="300" height="300">

This looks very similar to the <img> element, the difference being that it doesn't have the src and alt attributes. The <canvas> element has only two characteristics, width and height. If your renderings seem inaccurate, try designating your width and height attributes explicitly in the <canvas> attributes, instead of CSS. The width and height attributes default to 300 and 300, respectively. The id will be acclimated to initialize the canvas using JavaScript, and the text next to the equal to sign will be used as a call back when the mobile browser doesn't support it.

Drawing the background and spaceship for a game using HTML5 canvas and JavaScript

canvas = document.getElementById("spaceCanvas");
ctx = canvas.getContext("2d");
The variable canvas creates the canvas that we need to draw graphics objects, and ctx holds the rendering context. In this case it is a 2d graphics object.

This context contains the elementary methods for drawing on the canvas such as arc(), lineto(), and fill().

Next we paint the background black, place shiny asteroids on it, and draw the spaceship using the context object.

// Paint it black
          ctx.fillStyle = "black";
          ctx.rect(0, 0, 300, 300);

         // Draw 100 stars.
         for (i = 0; i <= 100; i++) {
         // Get random positions for stars.
         var x = Math.floor(Math.random() * 299)
         var y = Math.floor(Math.random() * 299)

          // Make the stars white
          ctx.fillStyle = "white";

          // Give the spaceship some room.
          if (x < 20 || y < 20) ctx.fillStyle = "black";

          // Draw an individual star.
          ctx.arc(x, y, 3, 0, Math.PI * 2, true);

Read more: Codeproject