update method
Implementation
@override
void update(double dt) {
// https://easings.net/ja#easeInElastic
var value = dt;
if (dt != 0 && dt != 1) {
var c4 = (2 * math.pi) / 3;
value = -math.pow(2, 10 * dt - 10) * math.sin((dt * 10 - 10.75) * c4);
}
innerAction.update(value);
}