Download the game .zip and unpack it into a directory <gamedir>.
Some fragmentation on this route now:
Chrome and derivatives, e.g. Opera or Chromium: Start the browser with option --allow-file-access-from-files.
Firefox: Set privacy.file_unique_origin in about:config to false.
Waterfox: Just open the index.html.
Pale Moon: Treats local files as cross origin and there seems no option for an override (=does not work).
MS Edge: Experience depends on Edge version. Edge (Pre-Chrome) on Windows 10: In explorer right-click index.html, then choose edge browser to open it. Edge (Chrome-based) on Mac: Open Shell. "cd <gamedir>". Then "/Applications/Microsoft Edge.app/Contents/MacOS/Microsoft\ Edge --allow-file-access-from-files index.html". On my old Mini Mac the Chrome based Edge has horrible performance. Using Waterfox instead.
Regardless of browser you can always run the game by utilizing a local webserver, e.g. if python 2.x is available:
You can use a different port as in the example.