It's an exe <= 65536 bytes. A modern OS does have gigabytes of external libraries, but the functions in them are more "support every graphics and sound chip out

It's an exe <= 65536 bytes. A modern OS does have gigabytes of external libraries, but the functions in them are more "support every graphics and sound chip out there" than "draw cool spaceship" and "play a funky beat". They're not allowed to obtain anything from the internet, nor anything else beside what comes as standard with the OS. Everyone gets the same base OS and compete against _each other_, so nobody gets a special advantage. If someone finds a clever way to use the base OS for more bytes (such as reusing the standard Windows fonts or MIDI soundfont or CAB compressor), then so does everyone else, and they use the saved space for even more cool and impressive stuff next release. Here's some tricks used for 4kb demos (some of which are applicable to 64kb demos too): https://in4k.github.io/wiki/aulds-4kb-introduction https://in4k.github.io/wiki/aulds-4kb-introduction https://in4k.github.io/wiki/aulds-4k-synth https://in4k.github.io/wiki/aulds-4k-synth https://in4k.github.io/wiki/exe-packers-tweakers-and-linkers https://in4k.github.io/wiki/exe-packers-tweakers-and-linkers