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/////////// ELASTIC EASING: exponentially decaying sine wave //////////////
// t: current time, b: beginning value, c: change in value, d: duration, a: amplitude (optional), p: period (optional)
// t and d can be in frames or seconds/milliseconds
Math.easeInElastic = function (t, b, c, d, a, p) {
if (t==0) return b; if ((t/=d)==1) return b+c; if (!p) p=d*.3;
if (a < Math.abs(c)) { a=c; var s=p/4; }
else var s = p/(2*Math.PI) * Math.asin (c/a);
return -(a*Math.pow(2,10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
};
Math.easeOutElastic = function (t, b, c, d, a, p) {
if (t==0) return b; if ((t/=d)==1) return b+c; if (!p) p=d*.3;
if (a < Math.abs(c)) { a=c; var s=p/4; }
else var s = p/(2*Math.PI) * Math.asin (c/a);
return a*Math.pow(2,-10*t) * Math.sin( (t*d-s)*(2*Math.PI)/p ) + c + b;
};
Math.easeInOutElastic = function (t, b, c, d, a, p) {
if (t==0) return b; if ((t/=d/2)==2) return b+c; if (!p) p=d*(.3*1.5);
if (a < Math.abs(c)) { a=c; var s=p/4; }
else var s = p/(2*Math.PI) * Math.asin (c/a);
if (t < 1) return -.5*(a*Math.pow(2,10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
return a*Math.pow(2,-10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )*.5 + c + b;
};