The aim of the game is to investigate the lost continent of Mu by completing 33 different missions of increasing complexity by working as a team, but with very limited communication permitted.
Each mission consists of a series of tasks and may have additional victory conditions and/or complications. For example, frequently the tasks must be completed in a certain order.
The game mechanic is similar to Whist or other trick-taking card games, except that the game is played cooperatively as a group. Mission tasks are completed by specific players winning tricks containing specific cards.
The deck consists of 36 Colour Cards (1 to 9 value in four coloured suits) plus 4 black Submarine Cards (1 to 4).
These 40 cards are shuffled and all cards are dealt out equally (although in a three player game, one player will have more cards than the others).
The player who has been dealt the 4 Submarine must act as the Commander for that mission. They receive the Commander Token to indicate this and must go first.
Each player also receives a grey Reminder Card and a double-sided Sonar Token, which are both placed in front of them on the table. The Sonar Token is initially placed green side up.
A double-sided Distress Token is placed face down in the centre of the table.
A deck of 96 Task Cards is shuffled and kept as a concealed pile. Each attempt at a mission will therefore have a random set of task cards, the sum of difficulty exactly equal to the requirement. On Board Game Arena, this is all handled behind the scenes.
There are 33 unique missions. Each mission describes the conditions under which it is played.
A number of tasks with sum of difficulty exactly same as specified by the mission are placed in front of the players. If some of the tasks causes the mission to be impossible, those are shuffled back into the deck and redrawn.
Unless otherwise specified by individual mission requirements, these are divided between the players. The Commander chooses first and then choice of task proceeds clockwise around the table until all tasks have been assigned.
Certain missions may have additional conditions. These are explained in the mission text.
A player completes a task by fulfilling the condition that is indicated on the task card. However, if the missions are impossible to complete only due to the mistakes of the players, this counts as a failed mission.
The Commander will have the lead at the start of the game. Play proceeds clockwise.
Highest card wins. A player must follow suit unless they have no cards of that suit.
The Submarines are trump cards and can only be beaten by higher value Submarines.
The winner of each trick takes the lead for the next trick.
As each trick is played, if all the tasks are compeleted and any other conditions are met, the mission is complete.
If winning the card has meant that any task / mission conditions have not been met, then the mission is instantly failed and must be replayed in order to proceed.
Once per mission, you may at any time click on your Reminder Card (in some browsers anywhere on the card except directly on the green Communication Token itself) to indicate that you wish to communicate some limited information about a color card in your hand to the other players.
Once you have clicked on the token, you will not be able to communicate immediately - there will be a communication phase at the start of each trick. By clicking on the token you indicate a desire to participate in the next available phase. If this phase has been triggered, communication then proceeds in clockwise order starting from the person with the lead. Only players who had clicked on their tokens prior to that phase may participate - if you forget to click in time, then you will have to try again ahead of the next round.
If you have selected the communication token during a trick but then change your mind when it gets to the communication phase, you may refrain from communicating and try again at the start of a future round (or not at all).
When communicating, you may choose a card in your hand to show to the other players. This card is then placed on the table under the Communication Token, which is then flipped to the red side to indicate that it has been used during this mission. You also pick up the grey Reminder Card which is placed in your hand to remind you and the other players that you still have a communicated card on the table.
The chosen card must be either:
- The lowest card you hold in a particular suit (token placed at bottom of card)
- The only card you hold of a particular suit (token placed in middle of card)
- The highest card you hold of a particular suit (token placed at top of card)
So if at any given moment you had the 1, 2, 5 and 7 of a particular suit, you would only be able to communicate about the 1 (lowest) or the 7 (highest), but not the 2 or 5 as they do not meet any of the 3 communication criteria.
The communicated card then remains face up on the table until it has been played. At that time the Reminder Card is placed back on the table.
Some missions may be difficult or impossible to complete due to the random nature of both the tasks and the cards themselves.
At the beginning of the mission, after the cards and tasks have been assigned, but before any communication has been made or cards have been played, the black distress signal token in the green mission briefing area may be activated. If this is done, the token is flipped and its use is logged.
Each player may then pass one of their cards to one of their neighbours. Submarine cards cannot be passed. All cards must be passed in the same direction; the players may agree upon the direction to pass.
If the tasks are possible to be completed after the passing, you must continue with the mission.
Additional Mission Conditions
Where indicated, communication is limited even further.
The basic communication mechanics (in terms of which cards you may choose to communicate) are unchanged, but the communication token must be placed in the centre of the card.
As a result, you can no longer tell what a player is communicating about a card (only that they have it, and that it is either their lowest, highest, or only card of that suit.
Rapture of the Deep
If a mission displays this symbol, place two fewer sonar tokens in the middle of the table than there are crew members playing. In other words, no crew member has their own token. Whoever wants to communicate takes one of these sonar tokens, without any discussion or announcement, and immediately communicates according to the usual rules.
If there are two or more sonar tokens in the middle of the table, a crew member can also communicate multiple times (or simultaneously). Once all the sonar tokens have been used, no more communication can be performed.
If a mission displays this symbol, a colour card is randomly drawn. A limit is applied according to the number:
- 1-3: Normal communation.
- 4-6: Currents.
- 7-9: Rapture of the Deep.
This lets you play the mission in real time. The number in the symbol represents the overall level of difficulty. Once the tasks are assigned, set the time on a device of your choosing.
You have to wait for the timer to start before playing any cards or communicating. If the time runs out before the mission is completed, you have failed.
You do not have to play in real time if you do not want to. In that case, simply perform the task allocation in the same way, but there will be communication restrictions or a higher degree of difficulty depending on the mission.
Free Selection of Tasks
If a mission displays this symbol, you are allowed to talk freely among yourselves about how to distribute the task cards, but you are not allowed to disclose which playing cards you have.
Discuss who wants to take which tasks and allocate them accordingly. The tasks do not have to be allocated evenly. One crew member is even allowed to grab all the tasks like an octopus.