"Escape" when no windows are open should bring up the Prefs menu, which also has the options for saving and quitting. This is a standard keybind in most games.

<r> I'm really enjoying the game but it could use some serious proofreading. There are a lot of awkward sentence fragments, and the game is sometimes inconsistent between British and American spelling. It also isn't sure how formal it should be, for example it sometimes uses overly casual terms like ...