I'm not really sure I could tell them apart in an ABX test. But it's not like the game is demanding in any way. The amount of sprites is way too low and they're all bitmaps. Furthermore, you don't need the webaudio api to playback an audio track and few effects concurrently, like this game does. Standard <audio> elements with the preload attribute work fine [1].

What I'd like to see is a comparison between 2D vector graphic performance of Flash compared to Web technologies as implemented in browsers. In my experience browsers are still very slow at that (without WebGL) while Flash had excellent performance for as long as I remember.

[1]http://robert.ocallahan.org/2011/11/latency-of-html5-sounds....