In After Effects, the expressions are scripts that are able to modify dynamically the value of the transformations of a certain object. It is a common practice using expressions for simulating physics in animations and produce realistic effects. They are also very useful because a well written expression could be applied on any object that should replicate that behaviour.

**Scripts in the tutorial:**

**BACKGROUND**

` v = thisComp.layer("slider").effect("Controllo cursore")("Cursore")*100;`

y = v*time;

yMax = this.height - thisComp.height;

if(Math.abs(y)<yMax ){

value - [0, y];

}else value - [0,yMax];

**M****AN (position)**

` pos=transform.position;`

yMax = thisComp.layer("background").height- thisComp.height;

v0 = thisComp.layer("slider").effect("Controllo cursore")("Cursore")*100;

t0 = yMax/v0;

if(time>t0){

t=time-t0;

y0 = thisComp.height/2;

amplitude = .9* thisComp.height;

period = 2*amplitude/v0;

omega = 2*Math.PI/period;

phase=0;

decay = 1/2;

y = amplitude*Math.sin(omega*t+phase)/Math.exp(t*decay) + y0;

x = amplitude*.09*Math.sin(omega*2*t)/Math.exp(t*decay) + pos[0];

[x,y]

}else value

**MAN (rotation)**

` yMax = thisComp.layer("background").height- thisComp.height;`

v0 = thisComp.layer("slider").effect("Controllo cursore")("Cursore")*100;

t0 = yMax/v0;

t180 = .3*t0;

if(time<t180){

value+180*time/t180;

} else 180;

**ROPE (initial point)**

` thisComp.layer("background").transform.position - value;`

**ROPE (end point)**

` thisComp.layer("bungeeMan").transform.position;`