Tween the progress() and timeScale() of an animation
In this video you will see that since tweens and timelines are JavaScript objects you can tween their getter setter methods like progress() and timeScale(). You can also tween getter setter methods in your own JavaScript objects. See demos here: https://greensock.com/tween-tween
Note that this video uses GSAP 2's formatting. GSAP 3 is now available! Check it out at https://greensock.com/3