Html5 appcache will download and cache resources indefinitely, and supports differential updates, but it's somewhat of a pain to work with and there are some br

Html5 appcache will download and cache resources indefinitely, and supports differential updates, but it's somewhat of a pain to work with and there are some browser-specific constraints on how big it can get. Using gz compression the size of the assets shouldn't be that much bigger than downloading a desktop game (which also takes a while).