I had the same thing - Firefox on Mac. The video area was 920px wide, but the video player was only 250x150px.
Also, I went to leave a comment on the stream and it asked me to log in. After jumping through the reset-your-password stuff and logging in I came back and tried to comment again (after refreshing). It said "you aren't logged in" (even though I am) and popped up the twitch homepage instead of the login box. The query param seemed to be something like ?popup=true, then it redirects to https://www.twitch.tv/?no-reload=true - which is just the twitch homepage.
[Edit: also, this is a really fun site! Excellent work!]
beautiful, thank you. I think this is the same css issue around twitch's embed iframe that someone else reported earlier. I'll try to get a fix up after I get off work today. Thanks for checking it out!