The OSX build... Simply doesn't work. You can however play the browser build on Mac.
Mac users using a non-standard keyboard layout (eg. french layout) have to switch back to the english layout for the numeric keys to be recognized.
On browser, if the window only shows a black screen after loading, try scrolling or resizing the window. It might be due to your Unity player being outdated, or to the browser itself.
If you notice a bug or want to give feedback, feel free to contact me !