Dynamic multiplayer online game

I've attempted to make an HTML 5 game before. Never finished anything but experimented with various concepts. This one is for real and since I'm the only person working on it, I'll keep the scope to minimum. On the other hand I want something that might, potentially, be fun to play from time to time. Here are some base concepts:

  • 2D multiplayer shooter. Sounds fun and doable
  • Browser-based, no plugins (i.e. pure HTML/JS/CSS)
  • Keep it simple, make sure you deliver
  • Use free graphics, from Open Game Art or something. LPC looks like a good start

And some technical ground rules based on problems with all my previous concepts:

  • Clear separation of back end and front end.
  • SocketIO is a wonderful library, but for a game you might need something lighter. Binary web sockets?
  • Select a good framework for the front end and stick to it. Needs research.
  • Back end: either Node or something python-based?