The difference is that Google had a clear unique value proposition that was to provide search results (and only search results) back extremely quickly and were highly relevant when they other players were focused on creating "web portals" and did not focus attention on search.
With CodeCombat and Codeacademy there UVP is very obvious (make learning to code a game and teach to code online resp.) and had not previously been done. With this site I don't understand what the UVP is (social programming challenges?) that hasn't been already by something like TopCoder, Sphere Online Judge, etc.
With CodeCombat and Codeacademy there UVP is very obvious (make learning to code a game and teach to code online resp.) and had not previously been done. With this site I don't understand what the UVP is (social programming challenges?) that hasn't been already by something like TopCoder, Sphere Online Judge, etc.