AlienStorm

AlienStorm is a multiplayer mobile friendly arcade game where players mission is to save the Earth from an alien invasion

Once in the welcome page you'll have to choose your player name and color. In this page you'll be offered with a room id which url you may copy and share with your friends (limited to 4 players for room). 

The cannon maybe managed with the onscreen controls or with the arrows keys to move the cannon and the space bar to shot when using a keyboard.

You also may play this game alone, but it'll be not as funny as playing with others :D