to tween you have to repeat every 0.0167 seconds modify (by example X position) to:
$radius*sin((repeats/20)*$speed)
-repeats is the number of repeats finished, found a bit at the bottom of the math section
-$radius is a number not equal to 0 that will make it move in a bigger radius
-$speed is well uh speed i guess
welcome to castle!! this app was made for games and not animating, so youll have to learn a bit of coding if you wanna do smooth animation, but you can always ask for help on the discord server!! or, you could also look at the deck source of decks that make those smooth animations and copy that
you could also keep on trying frame by frame, either way, good luck on figuring out what you like!!