Bloons TD, from Ninja Kiwi, is a strategy game that involves monkeys throwing darts at balloons. While most of the Bloons Tower Defense series is pay-to-download, this is the free-to-play version. With 18 different maps, you play against random opponents in one of three modes: Assault, Defensive, and Battle Arena.
In Assault Mode, the point is to send balloons to the enemy player and build your defenses against attack. For Defensive Mode, you try to outlast the competition in a never ending onslaught of balloon attacks. And with Battle Arena, players put down the medallion in-game currency as a bet with the winner taking all.
The game itself is pretty fun, but it requires a constant internet connection to play. It's also hard to click on some places in the map, and if you disconnect it's a loss. So if you are a fan of the Bloon series on armorgames.com, then this game can be something worth playing. But if you are looking for a less cartoonish vibe, check out number 7, Radiant Defense.