https://m.youtube.com/watch?v=ubaX1Smg6pY
Note that the laptop he is presenting on is not running Linux/Windows/OSX and that the presentation software he is using is not OoO/PowerPoint/Keynote. Instead, it is a custom productivity suite called "Frank" developed entirely by his team, running on a custom OS, all compiled using custom languages and compilers. And, the total lines of code for everything, including the OS and compilers, is under 100k LOC.