Bloons Tower Defense (also known as Bloons TD) is a series of tower defense games under the Bloons series produced and created by Ninja Kiwi. The game was initially developed as a browser game, built upon the Adobe Flash platform and released in 2007. Later games in the series expanded to support various mobile platforms, including Android, iOS, Windows Phone, PlayStation Portable and Nintendo DSi.
In the game, players attempt to prevent balloons (called bloons in-game) from reaching the end of a set course by placing towers along it; units which can pop the bloons in a variety of ways. It is also possible to freeze and, in later levels, glue the bloons, giving other towers more time to pop them. Money is gained by popping bloons and completing levels, and can be spent on extra towers or upgrades for existing ones or even special items such as exploding pineapples and monkey tacks.
The series has received mixed reception, with most games reviewed well. Some versions have been described as the best free tower defense games for their platform while criticism for the games has largely been due to lack of innovation in recent games and performance issues.