This isn't GPU intensive at all, but there's a lot of software and CPU overhead in WebGL compared to native OpenGL. This depends on your browser, the WebGL backend it uses (that would be Angle+Direct3D if you're on Chrome on Windows) and your CPU.
I got 24 fps with my high end GPU (and bad stuttering) with an old, poor CPU on Linux + Firefox. GPU is practically idle, but CPU is at 100% and fans are yelling.
Is butter actually smooth? In my experience butter is full of fat and hard to spread when it comes out of the fridge. Kinda the opposite of my reaction to this web app.
Many idioms are older than refrigerator technology. Butter is meant to be served at room temperature. A vessel called a butter crock preserves butter at room temperature by using a thin layer of water to create an airtight seal around an overturned cup of butter: http://i.imgur.com/oiNjjaW.png
