Correct, the demo I linked is a non-interactive audiovisual demo that is designed to show off the leet coding and artistic skills of the team. ;) The OP is a fu

Correct, the demo I linked is a non-interactive audiovisual demo that is designed to show off the leet coding and artistic skills of the team. ;) The OP is a fully-playable game, though. When designing a game, you probably have to code a game engine that has certain capabilities and certain restrictions that persist through the entire game. But for these demos, you can write an entire isolated program that runs one 15-second visual effect before flushing it out and loading something totally different for the next effect. The effects are also usually designed with a lot of tricks that make them inflexible (like preprocessed data tables) and usually also take up every CPU cycle available, leaving none for stuff like game logic.