A retro multiplayer shooter
Teeworlds is a free online multiplayer game, available for all major operating systems. Battle with up to 16 players in a variety of game modes, including Team Deathmatch and Capture The Flag. You can even design your own maps!
Basically, it’s a 2D sidescrolling shooter. The game is very easy to host and only 5MB in size. The great thing is that it is open-source and cross-platform.
It isn’t as easy as you might be thinking. But the game is real fun. A must try for everyone!
Ubuntu users can simply install by sudo apt-get install teeworlds teeworlds-server
For other platforms, you can go to this link – http://teeworlds.com/?page=downloads
A couple of tutorials have been provided below which you might really need.
[Tutorial] Host a server – [SERVER] Complete guide