These set of button animation in Pure CSS using the box-shadow property was designed by Giana. There are six animation to choose from Fill In, Pulse, Close, Raise, Fill Up, Slide, Offset. Some of these will work well for CTA buttons on your landing page.
If you are having trouble with the pen, try the archived copy on GitHub
Button Hover Animation Snippet
See the Pen Button hover effects with box-shadow by Giana (@giana) on CodePen.0