var game = new Phaser.Game(800, 600, Phaser.AUTO, 'phaser-example', { preload: preload, create: create });

function preload() {

    game.load.spritesheet('button', 'assets/buttons/number-buttons-90x90.png', 90,90);
    game.load.image('background','assets/misc/starfield.jpg');

}

var button;
var background;

function create() {

    //  Setting the background colour
    game.stage.backgroundColor = '#182d3b';

    // The numbers given in parameters are the indexes of the frames, in this order: over, out, down
    button = game.add.button(game.world.centerX, game.world.centerY, 'button', actionOnClick, this, 1, 0, 2);

    //  setting the anchor to the center
    button.anchor.setTo(0.5, 0.5);

}

function actionOnClick () {
    
    //  Manually changing the frames of the button, i.e, how it will look when you play with it
    button.setFrames(4, 3, 5);

}