As the resident Flash fan, lets not spread misinformation, folks.
Flash would run this game at a steady 120fps with no trouble, it's so simple.
This game isn't made in flash.
It is, like the title suggests, written in WebGL.
I'm not trying to cure anyone, I just like to watch that video whenever I feel my blood starting to boil when I read something the younger generation has written and include phrases like "That was Overdose Awesome".
That and Stephen Fry has a nice voice.
Pedantry is meant to fade as you become older and less angry...
https://www.youtube.com/embed/J7E-aoXLZGY?feature=oembed
If this doesn't bring you around I'm not sure what will...