Don't use left or top, bottom, margin or padding properties to move elements, but only "transform: translate".
In the same way, to resize elements use only "transform: scale" instead of height or width.
Left, top, bottom, margin, padding, height, width properties (and many others) force the browser to recalculate all the layout, so geometry of many elements, with a lot of CPU work.
Each property has a different weight, in this article it's clearly explained
high performance animations
Edit1: triggers.com seems to be a good page if you don't remember each property weight
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