FreeCiv is a free, open source 4x game inspired by “the history of human civilization”, and more specifically by Civilization, the proper noun commonly prefaced by Sid Meier. It’s been in ongoing development for 16 years(!), and is now available for HTML5 browsers, which means Chrome and Firefox.
You can start playing in FreeCiv’s web client now, and load up a single-player game in a matter of seconds. Select a username, use the numpad to distribute your starting units, and you’re away.
Alternatively you can play on the British Isles or Iberian Peninsula scenarios, and join/observe ongoing multiplayer games from the comfort of your work PC. Perhaps FreeCiv can become the new-old Neptune’s Pride?