It has its own compiler (Hemu-wasm) that allows you to write programs and run them natively in WebAssembly in the browser. This allowed the emulator itself Hemu (Holy Emulator) to be written in HolyC. The emulator is basically pure HolyC, and is under 2000 lines of code. Wayyy less bloated than QEMU-wasm and the performance is vastly better.