Menu at the top slides in or out depending whether you are scrolling up or down. While I appreciate it's fun to make moving things, this is unusual and very distracting.
Usual reading behaviour for a user isn't to read strictly from top to bottom – people scroll up and down as they read. This normal behaviour results in the polymer menu constantly flying in and out as a user is trying to read your content.
A good policy on animation and scroll logic is "no".

Menu at the top slides in or out depending whether you are scrolling up or down. While I appreciate it's fun to make moving things, this is unusual and very distracting.
Usual reading behaviour for a user isn't to read strictly from top to bottom – people scroll up and down as they read. This normal behaviour results in the polymer menu constantly flying in and out as a user is trying to read your content.
A good policy on animation and scroll logic is "no".