Well as I develop 3D games and have my own browsergame online I can tell you the differences.

The biggest difference is the step from "single shot" codes to a 4 dimensional (yes 4D, that's the tricky point) way of thinking and getting everything straight with framerate compensation not only for the current frame but also for acceleration (or wave attenuation), thus movements that develop beyond one frame.

Second are effects, maybe you wanna take a look at my game starbattle to learn some stuff abount effects (but it is programmed in C-Script).
Or watch the video to get some ideas.