WebAssembly (abbreviated Wasm) is "a binary instruction format for a stack-based virtual machine. Wasm is designed as a portable compilation target for programming languages, enabling deployment on the web for client and server applications." Currently, all major web browsers support Wasm. Standalone and embeddable Wasm runtimes also exist that allow running Wasm programs outside of the web browser.
So, to build all Pascal programs in the demo from source, three Free Pascal compilation targets are used:
Here's a screenshot of the user interface running on my desktop web browser in mobile-responsive mode: