Alice in Borderland Wiki
Four of Diamonds
Difficulty 4
Category Diamonds
Game Venue Closed Room
Status Cleared
Players Rizuna An
Taketo Serizawa
Unnamed Players (x2)

The four of diamonds was completed by beach members, Rizuna An, Taketo Serizawa, and two unnamed members. It was the second to last numeric card needed at the Beach, as well as the last Diamond card.

Game Overview


Player Limit: None

Time Limit: Until the water reaches the electrical wires

Prize: None

Once all players enter the room, it begins to fill with water. Dangling from the ceiling are 4 severed electrical wires.


  • In the room there is one light-bulb and a door to an adjacent room where there are three switches.
  • There is one switch that connects to the light-bulb.
  • With the door closed, players may flip any switch. While the door is open, players may only flip the switch once.
  • The door will not close if there are people in both rooms or a switch is flipped.
  • It is Game Clear if players can unanimously answer which switch turns on the light.
  • If the water level rises and the surface of the water touches the high current lines, it's Game Over.


The solution is surprisingly simple. Close the door, and flip switch A on for until the water is just a few inch sea from the wires. Turn the switch off, immediately open the door, and flip switch B. If it doesn’t turn on, it’s not switch B. Then feel the light bulb. If it’s hot, the answer is A. If not, then it’s C. This can be done in any order with any switch.


Explanation of 66% Probability

Rizuna An calculates that the initial solution proposed by a Beach member; where they daringly open the door, flip a switch, and should it remain off, then guess between the remaining 2 switches, has a 66% probability of yielding the correct answer, not 50%. This is because starting out by flipping any switch with the door open has a 33% of immediately revealing the correct switch at that point (bulb lights up). However, there is a 66% chance the bulb does not light up, then the players will have to guess between the two remaining switches with a 50% chance of being right. Therefore, the probability of successfully identifying the correct switch using this overall strategy is 66%; 33% (bulb lights up) plus 66%*50% or 33% (bulb does not light up, guess the correct switch from two remaining switches).


  • This was the first Diamonds game to be shown in the series.


Levers A, B, and C

An flips lever A

Four of Diamonds is cleared

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