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Clicking on "Categories" expands the Categories section and shrinks the Recent section. 
Clicking on any thumbnail causes the user to start watching a stream. The stream appears in the middle (it will simply be the livestream player) and the rest of the site around it will be dimmed.
When the user types something into the search box, a search result section appears and expands. The search result section has thumbnails of streams that match the search query.
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