How do I update my game automatically?

I have a game concept that requires the update of content such as new areas on the map, items, simple quests, etc.

The base of the idea is for the game experience to keep expanding and developing after the core game is done and out (the gameplay revolves around replay value). I would keep creating content in my spare time(assets, areas, items, etc) and would like for the game to sync with the latest version at the start of the player's run as seamless as possible. What are the different possible ways to achieve this? And is there a way to manage this without the need of the player to update the game manually? I'm hopefully targeting PC, MAC, and Linux. I understand that making it browser based might help me achieve this easier but would prefer a way to go about it with node webkit.

Thanks in advance!!!

So browser games autoupdate by themselves, seems it is the best way to go. Might try to just display the browser game in node webkit to keep the fullscreen no tab/window experience. I think it could also help me distribute/monetize the game easier as well.

Will there be complications by running the game from a url inside node webkit?

Does it sound like a safe way to distribute/sell the game and avoid piracy?