The last and greatest of the Flash Bloons titles (alright, technically BTD5 had a Flash version, but it was way worse than the Mobile and PC versions). It adds tons of new towers, including personal favorites like the Wizard and Bucaneer, as well as much more creative upgrades thanks to the introduction of higher tiers. Still relatively primitive compared to 5 and 6, but worth playing through the Ninja Kiwi Collection on Steam.