I've been playing this little online tank game for a while. It's an open source game. You play against other players online by connecting to a server. And the size of the game is small. It's 14 megabytes, yes 14, not 140, just 14 megabytes.
But don't let the size fool you, this game has an isometric view that means it's in the style of Red Alert.
It has a fast gameplay. The game has been around since 1999 and it has conquered my heart. You can download it from here : (just google the image below)