[1][2] In short, it aims to create the experience of retro gaming without the need to emulate a real console, allowing the developer to freely decide what specifications their fictional hardware will have.
One popular example of a fantasy console is the PICO-8, which was used as the platform for the original Celeste game.
There are some tools that aim to interconvert these console's cartridges automatically (including the scripts), but they are not perfect.
[6] Another example is the Gigadrive, an imaginary revision of the Sega Genesis designed by M2, who also developed an emulator of this system.
It is similar to a retro game emulator, but for a machine that never existed.As developer Björn Ritzl puts it, fantasy consoles simulate the restricted hardware of an old system packaged into a user-friendly experience with integrated tools for asset creation and game logic programming.