I should have included this in my first comment: this is a requirement from AMP to include the animation[1]: AMP HTML documents must contain the following

I should have included this in my first comment: this is a requirement from AMP to include the animation[1]: AMP HTML documents must contain the following boilerplate in their head tag. [...] <style amp-boilerplate>body{-webkit-animation: ... [1] https://www.ampproject.org/docs/fundamentals/spec/amp-boilerplate https://www.ampproject.org/docs/fundamentals/spec/amp-boiler...