My partner is an artist and streamer and, whilst playing some games, they run a bingo sheet where they'll predict what's going to happen in the game. After watching them do this in a photoshop window that they have to capture and share on stream, I made a site to keep track of the bingo sheet instead.
This is NextJS front-to-back with a MongoDB database. There's a page for viewers to see the current bingo sheet and a handful of admin pages behind a Discord login where my partner can create new bingo sheets and mark off squares on the current one.
The viewer side polls the server every ten minutes to update automatically, but there's definitely an improvement to be made here - I want to explore websockets to sync up the source of truth with all the client-side views.