The game accompanies a tutorial on how to make a real-time multiplayer game in Unity. It's published here so you can see what you would be making. You will need to invite a friend if you want to play I'm afraid. Or, just open it in two browser instances just to see what the gameplay looks like.
If you want something single player, check out my Galactic Empires, Asteroids, Cosmic Space Fortress or other game.