The secret project that went live on November 17th, 2023, was an emulator of the Tennis-for-Two game from 1958. It has been built for MuPIn - Museo Piemontese dell'Informatica - that held an exhibition of tennis (retro)videogames for the ATP Finals 2023.
Several videogames were on display and could be played, like the original Pong from 1972 up to a Wii.
There was a panel describing what should be the first videogame in history, the Tennis-for-Two developed to let visitors (taxpayers) of a USA laboratory interact with their technology. When I saw it I searched online for a modern emulator, found a 2008 project and I knew I could build it with parts I had at home.
So who visited the exhibition in the second weekend could play an emulator or Tennis-for-Two on a Tektronix oscilloscope.
Fun fact: people spent most of their visit-play time at Tennis-for-Two and Pong games.
The video above shows one of my tests on my Hameg analog oscilloscope, shot with the smartphone that didn't want to focus on the CRT trace. Please refer to the link above for the circuit diagram and firmware (ATmega168 and up).