public Builder then(FadedHandler handler) { fader.handler = handler; return this; }
public Builder every(int millis) { fader.period = millis; return this; }
public Builder by(double step) { fader.step = step; return this; }
public Builder to(double to) { fader.to = Math.max(to, 0); return this; }
public Builder from(double from) { fader.from = Math.min(from, 1); return this; }
public FadeAnimation start() { fader.start(); return fader; }