The base of 2D games is sprites, pieces of images composited (or blitted) on screen and which represent an object, character, or anything else animated or not. Sprites can be displayed with a transparency effect using the Alpha channel of an image. Typically, an image will contain several frames for a sprite, each frame representing a different animation step or different objects.
Editing sprite images
If you need a powerful multiplatform image editor, consider using GIMP, the GNU Image Manipulation Program. This program available on Windows, Linux and Mac OS X is really powerful and open source. You can download it at http://www.gimp.org/.
To implement sprites, we are going to rely on an OpenGL ES extension generally supported ...