thought this was going to be about things like https://en.wikipedia.org/wiki/Hybrid_Broadcast_Broadband_TV (hypertext on tv)

Same. Thanks; TIL about HbbTV: Hybrid Broadcast Broadband TV: https://en.wikipedia.org/wiki/Hybrid_Broadcast_Broadband_TV

Had been wondering how to add a game clock below the TV that syncs acceptably; a third screen: https://news.ycombinator.com/item?id=30890265