Hard Difficulty is the third and final difficulty in the Bloons Tower Defense 2-5 (not BTD5 Mobile) since the release of Bloons TD 2. At the beginning of a game, the player has half as many lives on hard as they do on Easy. In BTD2 and BTD3, hard difficulty has 50 Rounds. However, purchasing the towers is also pretty expensive in hard difficulty.
In Bloons TD 5, the player must pass Round 85, which is the first round with a ZOMG bloon, in order to win on hard difficulty. The Bloons move a little bit faster than on Easy Mode or Medium mode, and the player has only 100 lives. Towers are 8% more expensive than in Medium Difficulty. This difficulty is represented by a Robo Monkey, or by a Sun God in Extreme Tracks in its icon.