This is a web-based emulator that I have been working on for the META. Provide a compiled META .bin file, and it will attempt to run the program.
This is a work in progress. It is currently much slower than the actual hardware and lacking features like SD support and lights. However, the display and buttons work for most of the games I have tried.
The emulation logic is written in TypeScript, which is converted to JavaScript for the browser. The META program is processed similar to how the microcontroller would execute the program; each instruction is simulated. Millions of these simulated instructions are run every second. There is also logic for handling various peripherals. An html canvas is used to display what the user would see on the screen.