Bloons TD 6 expands on traditional Bloons Tower Defense gameplay with "Heroes", who will progressively level up once placed, making them stronger as the game progresses.[42][43] 3 "Tier 5" Monkeys of the same type can be merged with money and other copies of the monkey into extremely expensive but extremely powerful versions of themselves called "Paragons", combining the power of its constituent monkeys into a single strong monkey.[44] Certain maps contain obstacles that can prevent many monkeys from seeing or attacking over them.[45][43]