Campaign Mode

 is a new feature in Bloons TD 6. It is unlocked from the start, and has many stages. You must complete the Monkey Lane area before doing anything else in the game.

0-1: Learning the Ropes
Unlocked from the start. The first tutorial stage. You start with $350. Only Dart Monkeys are available on this stage. No upgrades. It only has a few rounds: Beating this grants 20 Monkey Money.
 * 1) 6 Red Bloons
 * 2) 10 Red Bloons
 * 3) 5 Red Bloons, 4 Blue Bloons
 * 4) 8 Blue Bloons
 * 5) 5 Green Bloons, 5 Blue Bloons, 5 Red Bloons

0-2: Cannons
Unlocked after beating 0-1. You start with $450. Dart Monkeys and Bomb Towers are available on this stage. No upgrades. It has a handful of rounds: Beating this grants 20 Monkey Money.
 * 1) 8 Red Bloons
 * 2) 14 Red Bloons
 * 3) 6 Red Bloons, 6 Blue Bloons
 * 4) 2 Green Bloons, 6 Blue Bloons, 3 Red Bloons
 * 5) 5 Green Bloons, 5 Blue Bloons
 * 6) 1 Yellow Bloon, 8 Green Bloons
 * 7) 4 Rushes of 6 Red Bloons
 * 8) 5 Rushes of 8 Red Bloons
 * 9) 2 Yellow Bloons, 10 Green Bloons, 14 Blue Bloons, 14 Red Bloons

0-3: Upgrading your towers
Unlocked after beating 0-2. You start with $200. Dart Monkeys and Bomb Towers are available on this stage. A Dart Monkey is already pre-placed on the track. Towers can be upgraded on both paths, up to Tier 1. It has tougher but still easy rounds: Beating this grants 30 Monkey Money.
 * 1) 4 Blue Bloons, 2 Red Bloons
 * 2) 20 Red Bloons
 * 3) 26 Red Bloons
 * 4) 34 Red Bloons
 * 5) 3 Yellow Bloons, 3 Blue Bloons
 * 6) 1 Pink Bloon, 1 Yellow Bloon
 * 7) 1 Pink Bloon, 2 Yellow Bloons, 4 Green Bloons, 8 Blue Bloons, 16 Red Bloons
 * 8) 3 Pink Bloons
 * 9) 4 Pink Bloons, 6 Yellow Bloons
 * 10) A rush of 60 Red Bloons
 * 11) 1 Purple Bloon, 1 Pink Bloon, 1 Yellow Bloon
 * 12) 6 Purple Bloons

Trivia
 I am Bramblewhisker  The EXE  04:04, June 2, 2015 (UTC)
 * After beating a level of campaign, you can unlock its track for 100 Monkey Money.