I want to make wave animation with a rectangle div by swing-like movement. Imagine you have a cup of water, and if you push the cup, the water will be moving & rotating(from front view) left and right and slowly returns to original position. I want to mimic that movement.   What I'm thinking is, 1. change div's `y` value (to move up) 2. when div starts moving up, it also starts moving & rotating left and right like swing does. 3. it slowly returns to or