Extreme Difficulty

 is a new Track Difficulty added to Bloons TD 5 on April 4, 2012. In order to play on any difficulty Monkey Money must be paid. When the player completes the Track he/she will receive a large amount of Awesome Points and a massive XP reward instead of Monkey Money. Saves are not permitted Bloons TD 5 Extreme Difficulty maps.

The icons for the three difficulties are the Sniper Monkey with Point Five Oh upgrade, the Ray of Doom and the Sun God/Temple of The Monkey God head, respectively.

Tracks
Currently, 5 Bloons TD 4 and 2 Bloons TD 5 Extreme Difficulty tracks exist:
 * Bloons TD 4
 * Jolly Roger
 * 1.21 Gigapops!
 * Bloonraker
 * Monkeys VS Bloons
 * MOAB-y Dick
 * Bloons TD 5
 * Main Street
 * Bloontonium Lab

Rewards
Note: Monkey Money rewards exclusive to Deluxe, while AP awards are for the online version only.

Trivia

 * This is the only difficulty that doesn't give Monkey Money rewards and actually costs Monkey Money to play, the other is the Special Agents Only mission.
 * If you play Reverse Mode on any of these tracks (in Bloons Tower Defense 5), it doesn't make a track easier/harder.
 * In Bloons TD 5 iOS, while selecting the difficulty for an Extreme track, the usual Baby Monkey, Mortar Tower, and Robo-Monkey icons are used rather than the Point Five Oh, Ray of Doom, and Sun God icons.
 * In Bloons TD 5 iOS, you could access Sandbox Mode. However, you still had to pay the 50$ Monkey Money fee to access an extreme track..
 * This is the hardest track difficulty in BTD5.
 * These tracks have to be unlocked at a certain rank before playing (50 for Main Street, and 60 for Bloontonium Lab).
 * On Bloons TD 5 Deluxe, Monkey Money is rewarded. However, they still require Monkey Money to play.