This version of the game lets you play against a friend on the same computer (easy since the game is played by taking turns) or online. It's as easy as picking the type of setting and your commanders.
The rest of the game is practically the same as the original Nintendo title. You have different types of units that fight better or worse against others. Infantry, air units, naval units, tanks ... each has its own strengths when completing certain tasks.
Custom Wars also comes with a very complete level editor that gives you the option to create and share your own maps. You can easily add anything to any scene (if needed, the game's manual explains the controls).
Custom Wars is an entertaining turn-based strategy game that, aside from lacking lots of different game modes (there's no story mode), can be really fun to play against a friend.