alt Hacker NewsThe legendary games programmer thing is a meme.
Casey is professionally best known for his work at RAD game tools (a highly successful middleware provider for game development back in the day), not games he himself developed.
What he is most highly regarded for is his teaching, particularly the Handmade Hero series on YouTube, which various programmers directly attribute as being responsible for their own professional success to a large extent.
He did work on the video games Dungeon Siege and The Witness afaik, but that's not what he is known for.
He also made one of the fastest terminal emulators (refterm), purely out of spite, to show Microsoft they were full of shit in their answer to an issue he posted to the Windows Terminal github. This directly led to performance improvements in Windows Terminal.
He mostly evangelizes non-pessimal software. He advocates that your program should only be a small factor like 3x slower than the hypothetical optimum - instead of 10000x slower as today's software often is. He compared Visual C++ 6's debugger on hardware from the time to current Visual Studio's debugger on current hardware, and found the former much faster when performing the exact same tasks on the exact same project file and code files.