Appearing footer

The footer should appear when the main scrolls by. This is done, but with JS at the moment. Would like to refactor this to CSS only!

This is the header

This is the main content

Lorem ipsum dolor sit amet consectetur adipisicing elit. Similique sapiente veritatis nam nemo repudiandae quos natus repellat provident quas ex quo minus corrupti culpa libero, facilis at impedit possimus dolore.

Lorem ipsum dolor sit amet consectetur adipisicing elit. Similique sapiente veritatis nam nemo repudiandae quos natus repellat provident quas ex quo minus corrupti culpa libero, facilis at impedit possimus dolore.

Lorem ipsum dolor sit amet consectetur adipisicing elit. Similique sapiente veritatis nam nemo repudiandae quos natus repellat provident quas ex quo minus corrupti culpa libero, facilis at impedit possimus dolore.

Lorem ipsum dolor sit amet consectetur adipisicing elit. Similique sapiente veritatis nam nemo repudiandae quos natus repellat provident quas ex quo minus corrupti culpa libero, facilis at impedit possimus dolore.