Challenge rule

Challenge rules are modifiers to the game rules of Bloons TD 6. They are used in Daily Challenges, Race Events, Boss Bloon Events, Contested Territory, Boss Challenge, Boss Rush, Quests, and Rogue Legends. In Odysseys, they are known as island rules and are separate for each island. Players can configure challenge rules for custom challenges in the Challenge Editor and Odyssey Editor, but with constraints on some rules, and there are some challenge rules that are not configurable and are only used in events.

Settings

Setting		Effect
	Max Monkeys	Limits the number of towers players can have on the map at the same time. "Default" means there is no limit. In Co-op, each player has their own limit.
	Starting Cash	Sets the starting cash, before any Monkey Knowledge or Relic Knowledge. "Default" means it uses the default amount of the selected difficulty/mode.
	Starting Lives	Sets the starting lives. The maximum lives are not shown to the player. "Default" means it uses the default amount of the selected difficulty/mode.
	Start Round	Sets the first round. "Default" means it uses the default amount of the selected difficulty/mode.
	End Round	Sets the last round. "Default" means it uses the default amount of the selected difficulty/mode.
	Least Cash	The player is required to complete the challenge with a limit on the total amount of cash they can spend. In Co-op, this counts the cash spent by all players.
	Least Tiers	The player is required to complete the challenge with a limit on the number of tiers they can purchase. The tier count increases by 1 each time the player places a base tower, upgrades a tower, or levels up a Hero with cash. In Co-op, this counts purchases made by all players.

Modifiers

Modifier			Effect
		Bloon speed	Multiplies the movement speed of non-MOAB-Class Bloons.
		MOAB Speed	Multiplies the movement speed of non-boss MOAB-Class Bloons.
		Boss Speed	Multiplies the movement speed of Boss Bloons. Not accessible in the Challenge Editor.
		Ceramic Health	Multiplies the health of Ceramic Bloons.
		MOAB Health	Multiplies the health of non-boss MOAB-Class Bloons.
		Boss Health	Multiplies the health of Boss Bloons. Not accessible in the Challenge Editor.
		Regrow Rate	Affects the rate that Regrow Bloons regenerate layers. Calculated by taking the reciprocal of the percentage and multiplying it by the 3-second delay between layers regenerating.
		Ability Cooldown Rate	Affects the rate that Activated Abilities recharge. Calculated by taking the reciprocal of the percentage and multiplying it by the cooldown.
		Removable Cost Rate	Multiplies the cost of removables and gizmos, or disables them entirely.

Rules

Rule		Effect
	Monkey Knowledge Disabled	Disables all Monkey Knowledge.
	No Lives Lost	Indicates that the max lives are set to 1. Does not appear if the max lives are set to "Default" when playing on Impoppable or CHIMPS.
	Selling Disabled	Prevents players from selling towers, except Champion Sentries, Sentry Paragons, Geraldo's Level 18+ Creepy Idol, and Special Poperations's Marine. Also disables Rare Quincy Action Figures.
	Powers Disabled	Disables all Powers (including Insta Monkeys) and Hero Boosters.
	No Continues	Disables continues.
	All Camo	All regular Bloons become Camo Bloons, including the children of MOAB-Class Bloons.
	All Regrow	All regular Bloons become Regrow Bloons, including the children of MOAB-Class Bloons.
	Custom Rounds	Indicates that the round does not use the default round set, or that it modifies it. Not accessible in the Challenge Editor.
	Double Cash Disabled	Disables Double Cash Mode.
	Fast Track Disabled	Disables Fast Track Mode.
	Paragon Limit	Restricts the number of Paragons that a player can have at a time. In Co-op, each player has their own limit. Not accessible in the Challenge Editor.
	No Round 100 Reward	Prevents the player from earning Insta Monkeys for completing rounds that are multiples of 100. Not accessible in the Challenge Editor.