A tween is declared first and played after, as many times as you like. tween.chain(a, b, c) plays tweens one after another, each step with no from starting where the one before left it, and tween.all plays them at the same time. Both are tweens too, so one goes inside the other, and they are what is played: their steps are not.
A field moved to makes the same trip each time it is played; one moved by goes that far again from wherever it is.
Click the preview first so it hears the keyboard. Space plays the door scene (again, from the start), K knocks the hero back sixteen pixels from wherever he is.