How to stop webpage from lagging when the gif background loops?

I'm working on a startpage for myself, and I decided to add the t-rex game you get from chrome offline mode.

I got it from this link: http://ift.tt/2jE6zMi

I have a .gif running as the background wall, and everytime the gif loops, there's a small stutter that kind of messes with the flow.

You can try it out here: tenumbra.com/home

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I'm thinking of converting the gif to .webm/.mp4 to load it as a video instead of a gif, but I'm having some difficulties with that but if you think that would work I'll try doing that.