Littlewargame is an HTML5 Real-Time-Strategy game with multiplayer mode and a map editor. It runs completely in your browser without any download, plugin or registration required. Just click 'play' and the game will start right away.
Homesite:
http://littlewargame.com/*You can register with the site to get a name. If you do not register you will be labled as a guest.
Wiki:
http://littlewargame.gamepedia.com/Little_War_Game_Wiki
