Co-Op Mode (BTD6)

"All Co-Op games share cash and hero xp [sic] evenly and double cash mode is disabled. For this game, you are playing: [Mode] – [Sub-Mode]"

- BTD6 Co-Op rules popup Co-Op Mode is a new mode added to Bloons TD 6 in an update that was released on 2nd July, 2019 for BTD6, on Version 11.0. It is unlocked at Level 20. It involves 2-4 cooperating on a random or private chosen game of BTD6 on a chosen map and difficulty.

Co-Op Mode can be accessed on the main menu. Players can either play on Quick Matches or create/join Private Matches. Each player will be assigned a specific number (P1, P2, P3, or P4) depending on their timing to a Co-Op Match.

Players are limited by their respective sides, usually a specific quadrant(s), unless the tower territory distribution is modified by a specific map. Some maps may have universal territories, as indicated by a colored "A" symbol, to represent an "All Players" territories. Players may only transport their own towers via Support Chinook only to within their allocated territory(s). Collectable items, such as bananas from Banana Farms, are only able to be picked up by the owner of the tower(s) that outputted the collectable items. In addition, other players cannot modify other players' towers or sacrifice them, with the only exception being Sun Temple and True Sun God/Avatar of the Vengeful Monkey sacrifices. However, abilities that lack the possibility of accidental sabotage such as Jungle's Bounty (counts everyone's Banana Farms in range) can become influenced or can influence other players' towers.

Every player starts with the same amount of cash minus $100 (-$50 in Half Cash). While playing the game, the full cash is gained for a particular player's cash account while popping bloons or generating cash. Players can share or request cash during the game on at anytime via the Co-Op Communication Menu on the right-hand side of the screen.

Before playing each game, players will be able to choose their own Hero; this is to be done before starting up Co-Op Mode, as there is currently no way to change Hero while waiting for players to connect to a Co-Op Mode game. In addition, players are allowed their own set of Tier-5 towers (i.e. up to 4 of a single Tier-5 on each side, up to 8 for Crossbow Master with special MK), which allows each player to decide on their own sets of Tier-5 towers without another disrupting other players' Tier-5 tower selection progress.

If one player has a given Monkey Knowledge upgrade, the upgrade is applied to all players. For example, if one player has the Bonus Monkey! Knowledge upgrade, every player will start with a free Dart Monkey. However, multiple instances of the same upgrade will not stack, so even if two or more players have the Bonus Monkey! upgrade, only one free Dart Monkey will be given to each player. If a Monkey Knowledge upgrade does not "apply to each player" and only contributes to the overall game instead of each player, then only one instance of any given upgrade will be used. For example, if a player has the Mana Shield Monkey Knowledge upgrade, only one instance of the Mana Shield will be present (i.e. only 25 bonus lives.)

(Additional rules to be added later)

Co-Operation
There is currently no chat option available in Co-Op Mode. However, players are able to request and exchange cash from one player to another with in-built functions. To access Co-Op related communicational commands, tap the Co-Op button on the right of the screen to open.

Once on the menu, the subject player may request cash by tapping "Request" button. Every other player will be alerted that the subject player requested cash by two alerts: an exclamation mark popup next to their player number, followed by an alert sound effect.

If the player(s) lose all their lives, any of the available players must press the Continue button in order to continue (unless CHIMPS Mode, Deflation Mode, or any other mode that limits use of Continues). Players may restart, but only players who presses restart will be redirected to a restarted match.

Special tower interactions
There are some interesting interactions that are worth noting that may cause changes in tower behavior and player strategy, including:
 * After ending each round, the total gained Hero XP is divided evenly to each player's placed Hero.
 * Level 4+ Benjamin's Skimming income generation will increase every player's income evenly (so +$0.5 per bloon for 2 players, $0.33 per bloon for 3, $0.25 for 4). This income generation, however, does not stack with other players' Benjamin Skimming income generation (?).
 * Jungle's Bounty (x4x Druid) affects all players' nearby Banana Farms within the Druid's own bounty range.
 * Super Monkey Fan Club (x4x Dart) affect up to 10 nearby Dart Monkeys regardless of owners, respectively. (?)
 * Plasma Monkey Fan Club (x5x Dart) affect up to 40 nearby Dart Monkeys regardless of owners. (?)
 * Total Transformation (x5x Alchemist) only affects the player's own towers. (?)
 * Spirit of the Forest (x5x Druid) on-track thorned bramble growths can stack with other Spirits of the Forest, producing extra damage to all bloons on screen.
 * Sub Commander (xx5 Sub), Energizer (5xx Sub), Prince of Darkness (xx5 Wizard), and other Tier 5 towers that add buffs to other towers do not stack their own buffs when multiple of them are placed. However, multiple Sub Commanders without the Sub Admiral MK can still add limited-range buffs to Monkey Subs nearby.
 * Trade Empire (xx5 Buccaneer) will stack effects with other player's Merchantmen. The parameters of this require further testing.


 * This section is incomplete. You can help by expanding it.

Maps
Unlike BTD5, all maps are available for Co-Op. However, each map has different territory distribution boundaries depending on the nature of the map. Some maps, such as Firing Range and all Expert Maps, do not have any boundaries; these maps are marked on the map display with a colored "A" symbol to indicate that all pieces of land are universal. The game uses the same configuration for 3-player games as it does with 4-player games, but one of the quadrants will be available to all players. The following key will be used to identify maps' configurations:
 * All = All players can place towers anywhere
 * Horizontal = Split a horizontal line across the center of the map
 * Vertical = Split by a vertical line down the center of the map
 * Down Diagonal = Split by a diagonal line from the top-left to the bottom-right of the map
 * Up Diagonal = Split by a diagonal line from the bottom-left to the top-right of the map
 * Straight 4 = Split into quadrants by a horizontal and a vertical line.
 * Diagonal 4 = Split into quadrants by 2 diagonal lines.


 * This section is incomplete. You can help by adding pictures of all of the maps.

Quick Matches
Quick Matches are publicly available, and there are three types of Quick Matches, all of which could have 2-4 players per match. Expert Maps, Deflation Mode, Apopalypse Mode, Half Cash, and C.H.I.M.P.S. difficulties cannot be encountered on Quick Matches. The following match modes are listed:

Completion
When successfully completed a game mode, there will be a two-page completion screen: the first page will include a list of useful statistics relating to each of the contributing players, alongside an image depicting the game's interpretation of the highlight statistic for each player:


 * This section is incomplete. You can help by expanding it.

Strategies
For a list of strategies relating to BTD6 Co-Op Mode, see Co-Op Mode (BTD6)/Strategies.

Bugs

 * If too many people join a private match at the same time, the co-op match can glitch. This was patched on version 11.1.
 * There is a known bug (commonly known as the "Thanos Snap") where if you reach a certain round, at the end of the round when the server refreshes the map many towers can disappear, which can be infuriating and may cost the game. This bug occurs due to poor server communication or when crashing other players from the game, and it is known to happen later in the game, usually at or around rounds 59-60, rounds 75-80, and rounds 90-100. Depending on the severity, it might only affect one player's towers or all the towers besides the ones placed early in the game.
 * If the above glitch occurs, one player might get the Defeat screen but the other players can get the Victory screen. Only the players who reach the Victory screen will get the rewards; the player who got the Defeat screen will earn nothing.
 * If a player leaves the game and the person who gets the leaving player's hero has the other costume of the hero active, it will change to the new costume when the hero levels up. For example, if the player who left had the regular Gwendolin skin but the new player who has Gwendolin has the Scientist Skin active, it will change to Scientist Gwendolin when it levels up. This also affects voice lines.
 * On version 11.1, sometimes the "P# has left the game" message can reappear for a number of times later.
 * In some cases, it might be impossible to give money to a player even though they are in the game.
 * If the server refreshes the map and the Pre-Game Prep MK is enabled, the road spikes will be reset after the refresh. Even if the road spikes run out, when the server refreshes, the road spikes will come back. It can particularly helpful on some maps like End of the Road, Haunted, and Quad.

Trivia

 * Ninja Kiwi released Bloons Tower Defense 6's Co-op mode in update 11.0, which allows up to four players to play at the same time.
 * Players cannot earn progress towards achievements such as Survivor or Inflated in the game; (Reaching round 100 on Apopalypse or Deflation respectively) however, these achievements can still be earned outside the game. (In Steam Achievements, Game Center, etc.)
 * For some tracks (such as Firing Range), players can place towers anywhere on the map.
 * In contrast to BTD5, even if all other players leave the game, a Co-Op medal will be awarded to the remaining player for a win.
 * If all players have the same hero, some buffs will not stack.
 * Since cash is evenly distributed between players, you'll earn cash slowly, so Benjamin is a recommended hero and it is recommended to use Farms.
 * If a co-op game is set to a map with quadrants, and a player left, the space for that player will be available to all players, also, the towers/powers that are left are also available to all players to access.
 * Unlike most Tier-5 towers, only one Avatar of the Vengeful Monkey may be on the map at any one time. In addition, other players' The Anti-Bloons and Legends of the Night will be disabled if an Avatar of the Vengeful Monkey is on the map.
 * It is possible on Quick Matches to be involved in difficulties that cannot be encountered by normal means, such as Easy Reverse or Medium Magic Monkeys Only. If these modes are completed, the player will only be rewarded for the Monkey Money and earn no medal for completion of the mode.
 * If the player completes a match for a mode that is not unlocked, the player will still earn the medal for completing the mode if the team wins. For example, if the player hasn't unlocked C.H.I.M.P.S. for the map but joins and completes a C.H.I.M.P.S. game for that map, the player will earn the C.H.I.M.P.S. medal despite not having the Impoppable medal.
 * Even though the badge for a red Co-Op C.H.I.M.P.S. medal exists in the game, it cannot be obtained as the player cannot leave a Co-Op game and come back, meaning that the players who complete C.H.I.M.P.S. on Co-Op will always get the black medal.
 * As of currently, Quad is the only Expert map to not be solved on Co-Op C.H.I.M.P.S.