Co-Op Mode (BTD6)

"All Co-Op games share cash and hero xp [sic] evenly. 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, on Version 11.0. Unlike Bloons TD 5 Mobile, Co-Op Mode must be unlocked by reaching Level 20. It utilizes a peer-to-peer connection that involves 2-4 players 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 when they joined the Co-Op lobby. Players can leave and re-join at any time during the Co-Op match, but there are still risks to leaving a 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, True Sun God/Vengeful True Sun God and Paragon 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) for 2-Player, and minus $50 per additional player (-$25 per additional player in Half Cash). If the "More Cash" MK is unlocked by any player, it will be distributed evenly among each player. 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 Heroes 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 "Master Double Cross" MK enabled), 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.)

Additionally, Co-Op Daily Challenges may appear around 2 times per week; one on Sunday and another on Wednesday.

Co-Op functionalities
Players are able to request and exchange cash from one player to another and send emotes 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. The player can also tap the emotes button to open a list of emotes, which can then be sent to other players. The other players will be alerted of the emote by the subject player.

Players can mute other player's cash requests or emotes by pressing that player's mute button on the menu.

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.

Available emotes
Here is a list of the available emotes that can be sent to other players.

Default emotes
These emotes are provided to the player at the start.
 * "Hi!"
 * "Ready!"
 * "Well done"
 * "Good job"
 * "Thanks"
 * "Sorry!"
 * "Slow!", likely to be used when needing to turn off Fast Forward
 * "AFK" (away from keyboard)
 * "GG" (good game)
 * A laughing Monkey head
 * A Monkey head giving a thumbs up
 * A Monkey head giving a thumbs down
 * A dizzy Monkey head, resembling the one shown on the Defeat screen
 * A crying Monkey head
 * A green camo bloon, likely to be used to signify rounds with camo such as rounds 24, 42, and 51.
 * A Lead Bloon, likely to be used to warn against rounds with lead bloons such as rounds 28 and 59.
 * A Zebra Bloon, Rainbow Bloon, and Ceramic Bloon, likely to be used to signal against thermal bloons or rainbow/ceramic rushes such as rounds 26, 63, 76, and 78.
 * A MOAB, BFB, ZOMG, and BAD, likely to be used to notify others to prepare MOAB defenses against rounds such as 40, 64, 75, and rounds past 80.
 * Ability icons for Fire Cocktail, Concussive Shell, and Brambles, to represent use of hero abilities.
 * A piggy bank, likely to notify others about farming or to collect Monkey Banks.
 * Icons of Support Chinook health crate, Jungle's Bounty, and Merchantmen, likely to notify others about farming.
 * The hero icons of each hero that the players on the team is using.

For a list of possible interpretations of each default emote, see Co-Op Mode (BTD6)/Strategies.

Trophy Store emotes
These emotes have to be bought at the Trophy Store before they can be used.

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 can be stacked with other players' Benjamin Skimming income generation. (Tested in patch 22.2)
 * 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 20 nearby Dart Monkeys regardless of owners. (?)
 * Total Transformation (x5x Alchemist) affect towers regardless of owners.
 * 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.
 * Shinobi Tactics and Poplust buffs can only stack up to 20 times and 5 times, respectively, towards their respective towers (Ninjas and Druids, respectively), regardless of player ownership.
 * Alchemist buffs and Monkey Village buffs can target any players' towers.
 * Multiple Obyn Greenfoots use their own respective Wall of Trees for each respective player.
 * Overclock and Ultraboost abilities may be used on any available tower, regardless of player ownership.
 * Adora can only sacrifice towers owned by the player who owns her.
 * The "Come On Everybody!" MK is separated from each player, and thus is treated for each player as though the other players' Primary Monkeys do not exist.
 * Admiral Brickell's Mega Mine can be placed on any area of water, regardless of player ownership.
 * Benjamin's per-round income is given only to the player who owns Benjamin.
 * Bloon Traps and XXXL Trap rewards are given to the successful trapper.

Other special interactions

 * Hero levelup voicelines are randomized differently from player to player.
 * Jukebox settings are not shared with other Co-Op members.
 * Achievement-earned settings (e.g. Big Monkey Towers Option, Small Bloon Option) are set to whatever the player has set, rather than appearing on other players' screens.
 * Pausing the game by the settings menu does not affect Co-Op connection, but certain actions that trigger pausing (e.g. pulling the status menu on iOS devices) will cause a temporary loss in Co-Op connection.

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: Co-op daily challenges can overwrite a map's configuration.
 * 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.

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, Alternate Bloons Rounds and Impoppable on Beginner 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.

Co-Op Events
Two Co-Op events exist:
 * Co-Op Challenges, which have additional challenge restrictions added on top, and are run by Ninja Kiwi.
 * Co-Op Boss Events, played in multiplayer for the currently running Boss Event.

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.
 * Players used to not 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.). 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. While this glitch can still happen, it's now less likely to occur since version 12.0.
 * It was presumed that having an IMF Loan could be the cause of activating this glitch, but this was proven false when this glitch even occurred on C.H.I.M.P.S.
 * 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.
 * Since 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. This has been patched around version 12.0.
 * 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 be particularly helpful on some maps like End of the Road, Haunted, and Quad.
 * This has been adjusted with the new restart mechanic on version 13.0; now whenever the server refreshes, all of the Pre-Game Prep road spikes will disappear.
 * When restarting a Co-Op Game with the "Restart" button, the free Dart Monkey from the "Bonus Monkey" MK does not become available again. This does not occur for the "Military Conscription" halved Military Monkeys MK.
 * Likewise on older versions of the game, restarting a Co-Op game may keep all Ceramic Bloons from MOAB-Class Bloons "Super Ceramics", even before round 81.
 * On version 12.0, there are numerous disconnections that may happen suddenly or even before the round starts.
 * On version 12.0, it might be impossible to place towers on a certain part of the map after a player has left. This does not happen on maps where the player can place towers anywhere at the start.
 * In Co-Op Challenges, the available hero emotes will always be the hero the players starts with before starting the challenge, even if it the hero is forced and no one has the hero prior to starting the challenge. This can result in players having emotes of other heroes that cannot be used in the challenge.
 * Co-Op Challenges does not display rewards correctly on the teammate screen, but will appear correctly after the Co-Op Challenge is complete.
 * If the game is lagging, you might be able to stack other towers on top of each other while waiting for the server to communicate.
 * If the player selects a tower and then another player upgrades that tower, the upgrade paths won't update even though the artwork updates
 * If that upgrade causes a path to become locked, sometimes that path's upgrade shows as costing 3.422823*10^38. This is likely due to locked upgrades supposed to be unpurchasable.
 * This can also occur if the player upgrades their tower, then unselects and reselects that tower before the upgrade appears.
 * If the player then tries to upgrade that tower, the upgrade will work if the player can afford the actual upgrade for that path, and the price glitch occurs if a path becomes locked by that upgrade.
 * If the player has the jukebox enabled and leaves an in-progress co-op game, the music from the game plays on top of the main menu music. This seems to only occur when a round is in progress.
 * Spillway cannot be played in co-op on version 18.1 due to a bug with the map crashing upon starting.
 * Even if all players left the game, the latency for placing towers and starting rounds stay the same.
 * Rarely, the game can get stuck when refreshing. This renders the match unplayable as the next round never starts.
 * during a refresh or occasionally when a player has poor connection, the game runs noticeably slower
 * When the game is running slower, all tower animations/particles, and animations for hiding/revealing the power, ability, and co-op emote menus run slower, and bank deposit animations loop. Other menus work at normal speed

Differences between BTD5 and BTD6

 * All maps can be played in Co-Op mode

Sounds
When player requests cash:
 * [notify sound]

When player disconnects:
 * [dial down sound]

Trivia

 * Ninja Kiwi released Bloons TD 6's Co-op mode in Version 11.0, which allows up to four players to play at the same time.
 * 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(s) for a win.
 * If all players have the same hero, some buffs will not stack.
 * 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.
 * Towers/powers are distributed evenly between the remaining players.
 * In Co-Op Daily challenges with limited towers and/or limited max monkeys, unused towers are distributed evenly too.
 * If players can use their own hero, and a player disconnects, another player can use that hero, allowing 2 or more placeable heroes.
 * Unlike most Tier-5 towers, only one Vengeful True Sun God 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 a Vengeful True Sun God 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 normally 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.
 * All of the maps have been solved on Co-Op C.H.I.M.P.S.


 * List of confirmed achievements that are shared in Co-op
 * Perfect Paragon
 * Even if another player placed the paragon, the player will get the achievement.
 * Student Loans
 * Even if another player went into debt, the player will get the achievement.