Bloons TD Battles is a game by Ninjakiwi that allows you to play with another person, in a 1 vs 1 match of Tower Defense.
There are 2 modes:
Assault- Send bloons to the opponent, and increase your income
Defense- No sending bloons, you must increase income by getting more money and buying the income upgrades
There are private matches available just in case any of us wants to play together without having to wait for us to join in a public match.
By playing more, you get more battle points which unlocks more towers. And by winning you get Medallions, which allows you to get the other Tiers for towers.
You have to register to play, but it's fun even if you have to register.
To play in a private match, go to Private Match on the main menu, and click CREATE BATTLE if you are the host. You will be given a Battle ID. Copy it to your clipboard by clicking the copy button that looks like a clipboard, and give it to others. They must enter the Battle ID on the private match area.
So, post your matches, Ninjakiwi accounts (I guess) and have some fun in private matches.
Also, you should play the Bloons games in general (specifically Bloons TD 5), because those are fun and aren't multiplayer if you don't play multiplayer.