Challenges

Challenges, in BTD4, are where you have to beat a certain level under certain restrictions. The challenges are:

Ocean Road
Difficulty: Medium

Objective: Beat this track on Medium using only Dart Monkeys and Super Monkeys.

Ant Hill
Difficulty: Hard

Objective: Beat this track with only one life.

Ocean Road
Difficulty: Easy

Objective: Same as above.

World Tour
Difficulty: Medium

Objective: Beat this track without using Glue Gunners or Ice Towers.

Military Base
Difficulty: Medium

Objective: Beat this track with Dart Monkeys and Tack Shooters disabled.

River Bed
Difficulty: Medium

Objective: Beat this track using any tower, but at most three of each kind.

Bus Route
Difficulty: Medium

Objective: Same as Ant Hill on the computer.

Cactus Creek
Difficulty: Hard

Objective: Beat this track using only Boomerang Throwers, Glue Gunners, and Mortar Towers.

Snow Trail
Difficulty: Hard

Objective: Beat this track using only the Monkey Apprentice, Ice Towers, and Bomb Towers.

Go Bananas
Difficulty: Medium

Objective: Deflation-mode challenge, where you start at round 40 and have to make it to round 85.

Trivia

 * Road items (Road Spikes, Monkey Glue , and Pineapples) are available on any challenge, including those that have limited towers.
 * Oddly enough, Monkey Glue is available on the challenge that says "no slow".