NOW UPDATED WITH NEW THE NEW TOWERS!
Use your favourite new towers, the Dartling Gun and the Spike Factory in this awesome expansion pack for BTD4. Bloons Tower Defense 4 Expansion contains 4 brand new crazy fun tracks for you to try out. Mesmerise yourself on the Sandy Spiral Track, get lost in the Subterrainian Sewers, explore the secrets of the Monkey Temple, or challenge your wits on the Triangle of Insanity! This expansion also includes a new game mode called Deflation mode. You start Deflation mode with 50,000 money but you never get any more. Finally, we have included Tower Specialties, which you will unlock after completing the new tracks in various difficulty levels. The specialties allow you to customize your strategy by making some towers much cheaper to buy, at the expense of increasing the cost of all others. Enjoy Bloons Tower Defense 4 Expansion only on Ninja Kiwi!
Source: The Developer Website.