In 2004, a German demoscene group released a game called .kkrieger.
It was a full 3D first-person shooter with dynamic lighting, textures, sound effects, music, and monster AI.
The entire executable was 96 kilobytes. Instead of storing images and audio files, they wrote C++ and Assembly that generated the 3D meshes, textures, and sound waves mathematically in RAM when the game booted.
Today, a single website's "Accept Cookies" banner is 10x larger than that entire 3D game.