This is OpenTTD built as WASM application, allowing to play it in browser. It lacks some features (multiplayer, sounds and custom font support) but otherwise it works like native one. While it can be opened in mobile browsers, it is desktop version so you cannot play due to unadapted UI and controls. See instruction to create WASM build youself.
I've added extension bar that adds possibility to export or import save files, heightmaps etc. To save file from virtual filesystem, click "Export" button, navigate through virtual filesystem and click on file. To import file from computer, click "Import" button, navigate to target folder and select file using file control below. To close import/export dialog, just click outside of it.