phaser/examples/physics/launcher.js

// mods by Patrick OReilly
// twitter: @pato_reilly

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

function preload() {

    game.load.image('analog', 'assets/tests/fusia.png');
    game.load.image('arrow', 'assets/sprites/longarrow2.png');
    game.load.image('ball', 'assets/sprites/pangball.png');    

}

var arrow;
var ball;
var catchFlag = false;
var launchVelocity = 0;

function create() {

    // set global gravity
    game.physics.gravity.y = 200;
    game.stage.backgroundColor = '#0072bc';
    
    var graphics = game.add.graphics(0,0);
    graphics.beginFill(0x049e0c);
    graphics.drawRect(395, 350, 10, 250);

    analog = game.add.sprite(400, 350, 'analog');
    analog.body.allowGravity = false;
    analog.width = 8;
    analog.rotation = 220;
    analog.alpha = 0;
    analog.anchor.setTo(0.5, 0.0);
    
    arrow = game.add.sprite(400, 350, 'arrow');
    arrow.anchor.setTo(0.1, 0.5);
    arrow.body.allowGravity = false;
    arrow.alpha = 0;
    
    ball = game.add.sprite(100, 400, 'ball');
    ball.anchor.setTo(0.5, 0.5);
    ball.body.collideWorldBounds = true;
    ball.body.bounce.setTo(0.9, 0.9);
    
    // Enable input.
    ball.inputEnabled = true;
    ball.input.start(0, true);
    ball.events.onInputDown.add(set);
    ball.events.onInputUp.add(launch);

}

function set(ball, pointer) {

    ball.body.velocity.setTo(0, 0);
    ball.body.allowGravity = false;
    catchFlag = true;

}

function launch() {

    catchFlag = false;
    
    arrow.alpha = 0;
    analog.alpha = 0;
    Xvector = (arrow.x - ball.x) * 3;
    Yvector = (arrow.y - ball.y) * 3;
    ball.body.allowGravity = true;  
    ball.body.velocity.setTo(Xvector, Yvector);

}

function update() {

    arrow.rotation = game.physics.angleBetween(arrow, ball);
    
    if (catchFlag == true)
    {
        //  Track the ball sprite to the mouse  
        ball.x = game.input.activePointer.worldX;   
        ball.y = game.input.activePointer.worldY;
        
        arrow.alpha = 1;    
        analog.alpha = 0.5;
        analog.rotation = arrow.rotation - 3.14 / 2;
        analog.height = game.physics.distanceToPointer(arrow);  
        launchVelocity = analog.height;
    }   

}

function render() {

    game.debug.text("Drag the ball and release to launch", 32, 32);

    game.debug.bodyInfo(ball, 32, 64);

    // game.debug.spriteInfo(ball, 32, 64);
    // game.debug.text("Launch Velocity: " + parseInt(launchVelocity), 32, 250);

}