Cannonball and Slingshot - The Essential Guide to HTML5 - page 130

Code Explanation

var cheight = 600;

var ctx;

var canvas1;

var everything = [];

var tid;

var startrockx = 100;

Starting position x

var startrocky = 240;

Starting position y

var ballx = startrockx; Set ballx

var bally = startrocky;

Set bally

var ballrad = 10;

var ballradsq = ballrad*ballrad;

Save this value

var inmotion = false;

var horvelocity;

var verticalvel1;

var verticalvel2;

var gravity = 2;

var chicken = new Image(); Name of original target

chicken.src = "chicken.jpg"; Set image file

var feathers = new Image();

Name of hit target

feathers.src = "feathers.gif"; Set image file

function Sling(bx,by,s1x,s1y,s2x,s2y,
s3x,s3y,stylestring) {

Function defining a slingshot based on the four
points plus a color