Open any button, copy the HTML into your markup and the CSS into your stylesheet. Every button is a real <button>, so it is focusable, works with the keyboard and submits forms. No JavaScript is involved, even for the click and state animations.
To change the color, set --btn-color on the button or any ancestor. To change the size, set --btn-size: padding, radius, borders and shadows are all in em, so the whole button scales from that one value.
Press and click effects use :active and :focus-visible, so they play for mouse, touch and keyboard. Every snippet ships with a prefers-reduced-motion rule that turns the motion off for people who asked their OS for less of it.