math.smoothstep

math.smoothstep takes e0, e1 and x.

math.smoothstep(e0, e1, x)

function update(dt) {  math.smoothstep(1, 1, 0);}

math.smoothstep is called with values of the shape its signature asks for. The code sits in update(dt), which the engine calls every frame: dt is the time since the last one, in seconds.