Doors
Doors are a central gameplay mechanic in Blue Prince. Doorways lie at the boundary between each room in the house, and it is only by interacting with doors that drafting can be performed to create new rooms.
At the start of each day, the only doors in the house are those in the doorways of permanent rooms, most significantly the Entrance Hall. These doors are initially closed with no actual rooms behind them until the player drafts a floorplan by interacting with a door, which creates the room and causes the door to open. Most rooms other than Dead Ends will contain their own doorways, with their own doors, which allow new rooms to be drafted, and so on and so forth. Like rooms, these doors all reset at the end of each day.
Some doors are locked, and require either a key or a Keycard to open before drafting may commence. Several other types of doors exist for purposes other than drafting.
Normal doors
The most common type of doors in Blue Prince are not typically given a specific name and are usually just called doors, normal doors or drafting doors. These are the doors found in the doorways of almost every room, including the permanent rooms that already exist in the house at the start of each day. Any closed door can be interacted with, which will initiate the drafting process unless it is locked.
Each draftable room has a number of doorways, whose quantity and position depend on the room's shape. Whenever a new room is drafted, each of its doorways is checked to see whether or not it can spawn a door, excluding the doorway connected to the drafting door. If there is space behind the doorway for another room to be drafted, then a new door is created, ready for drafting. If the doorway leads directly into an existing room, then one of two things happens:
- If the doorway directly connects to an existing doorway, then no new door spawns and the existing door automatically opens, becoming uninteractable. This happens even if the door is locked or security locked.
- If the doorway leads directly into a wall side of an existing room, then no new door spawns and the doorway appears boarded up and inaccessible.
On the rare occasion that a doorway is positioned so that it leads outside the house, that doorway is also boarded up.
If a room is drafted in the position that an existing doorway leads to, but with no new doorway connecting to it, then the existing door is destroyed and the doorway is boarded up.
Locked doors
When attempting to draft from a door, there is a chance that the door may be locked. The chance depends on several factors, including the rank within the house and the number of locked doors already encountered today. Doors found anywhere in ranks 1 to 3 are never locked by chance.
A small number of rooms have doors which are guaranteed to be either locked or unlocked:
- The Corridor's door is always unlocked.
[Upgrade Spoiler: Courtyard] Both of the Corriyard's doors are always unlocked.- The opposite drafting door in the Great Hall is always locked. It also has six side doors which are always locked and, uniquely, do not automatically lead to a draft. Two of those doors lead to actual drafting doors, which are guaranteed to be unlocked.
[Studio Addition: Vestibule] When entering the Vestibule, all of its doors close, including the door that it was drafted from. One of those doors is randomly chosen to be locked, and the other three are all guaranteed to be unlocked. Opening any of those doors only leads to a draft if there is not already a room behind them.
When attempting to draft from a locked door, a prompt will appear saying that the door is locked. There are three unlock options that may appear when attempting to unlock the door:
- Use
- An option which is available if one or more keys are held. Spends a key to unlock the door.
- Special keys
- An option which is only available if one or more certain types of special key are held. Shows a dropdown menu that lists the keys and allows any of them to be attempted. Many special keys have restrictions on where they may be used; attempting to use a special key incorrectly will display the message "THE KEY DOES NOT FIT" without spending it. Most special keys of this type are consumed on use and have additional effects beyond just unlocking the door.
- Lockpick Kit
- An alternate interaction prompt which is only available while holding the Lockpick Kit. Allows one attempt to pick the lock without using any keys or special keys. If successful, the door unlocks and drafting begins. Otherwise, a message appears saying "You don't seem able to pick this door's lock." Exiting the menu and trying again will display the message "This door's lock still seems too difficult to pick."
There is also an option to exit the menu, which is only possible when interacting with a locked door as the drafting process is usually inescapable once initiated. If none of the three unlock options are available, the usual menu does not appear at all and a simple message prompt appears instead that just says "locked."
Beyond the Estate
This section contains datamined information about chances of locked doors. It may contain spoilers for various stages of the game.
A door being locked or not is determined dynamically the first time the door is clicked. Doors that have not been clicked yet are referred to in this section as unchecked doors. (If a door is clicked and turns out to be locked, then you exit, it is no longer unchecked.)
Each door in the house has a base chance to be locked, based on its position:
| A9 | 130% | B9 | 130% | C9 | 130% | D9 | 130% | E9 |
| 130% | 130% | 130% | 130% | 130% | ||||
| A8 | 110% | B8 | 110% | C8 | 110% | D8 | 110% | E8 |
| 90% | 80% | 80% | 80% | 90% | ||||
| A7 | 70% | B7 | 70% | C7 | 70% | D7 | 70% | E7 |
| 70% | 60% | 60% | 60% | 70% | ||||
| A6 | 60% | B6 | 60% | C6 | 60% | D6 | 60% | E6 |
| 60% | 60% | 60% | 60% | 60% | ||||
| A5 | 45% | B5 | 45% | C5 | 45% | D5 | 45% | E5 |
| 45% | 45% | 45% | 45% | 45% | ||||
| A4 | 25% | B4 | 25% | C4 | 25% | D4 | 25% | E4 |
| 0% | 0% | 0% | 0% | 0% | ||||
| A3 | 0% | B3 | 0% | C3 | 0% | D3 | 0% | E3 |
| 0% | 0% | 0% | 0% | 0% | ||||
| A2 | 0% | B2 | 0% | C2 | 0% | D2 | 0% | E2 |
| 0% | 0% | 0% | 0% | 0% | ||||
| A1 | 0% | B1 | 0% | C1 | 0% | D1 | 0% | E1 |
These chances are then multiplied by the bias value, giving the true chance that the given unchecked door becomes locked or not.
The bias value starts at 1 each day, increases if an unchecked door ends up unlocked, and decreases if it ends up locked.
- If the chance for the door to be locked was more than 100%, the game does a second roll with the base chance (ignoring bias). If this roll passes, the bias value does not change (otherwise continue to next line).
- If the door was locked, the bias value is reduced by 0.385 or set to 1, whichever would result in a lower value.
- If the door was unlocked and the chance for the door to be locked was less than 31%, the game does a second roll with the base chance (ignoring bias). If this roll fails, the bias value does not change (otherwise continue to next line).
- If the door was unlocked, the bias value is increased by 0.35 or set to 1, whichever would result in a higher value.
If a door's state is guaranteed to be locked or unlocked through Corridor, Great Hall, Corriyard, Vestibule, or being a security door, it is not unchecked and thus bypasses this entire system.
If a door gets unlocked by an external effect, such as through Foyer, Kennel, or Shelter, it still counts as unchecked, thus applying this system and changing the bias value. However, it will then ignore the result. (The bias value changes according to whether it would have been locked were it not already unlocked due to these effects; it does not assume it was always unlocked.)
The consequence of this system is that doors on high ranks can be unlocked if special care is taken to reduce the bias value through encountering locked doors on lower ranks before checking those doors, and doors on low ranks can be more likely to be locked (to use special keys on them) if the bias value is increased first.
Security doors
Security doors, also called security locked doors, are special doors that have a chance to replace normal doors. Security doors begin to appear starting from the northwards doorways of Rank 3, and increase in frequency with higher rank, similarly to regular locked doors. Only certain rooms can contain security doors, including most Mechanical Rooms and Red Rooms that are not also Dead Ends. There is a limit to how many Security doors can generally appear, and they never replace doors which are guaranteed to be locked or unlocked.
Unlike regular doors, security doors themselves are not interactable and require the use of a nearby keycard reader. The keycard reader has three glowing LEDs that indicate whether the security door is locked, unlocked or offline. All security doors are initially locked, and attempting to interact with them will display a prompt saying "This security door is locked by electronic keycard".
If a Keycard is held while interacting with the keycard reader, the red lights turn green as the security door unlocks and drafting begins. Security door drafts have a unique interface, which also shows the rarity of each drawn floorplan represented by the number of green LEDs above.
Drafting into a security door will automatically open it, the same as any other door.
Spoilers Within
This section contains spoilers for the keycard system.
Security doors are controlled by a keycard system which modifies their frequency and behavior. Two settings for the system, Security level and Offline mode, can be changed by using the Security terminal. The power to the keycard system can be toggled using the switch in the Utility Closet. All three settings reset each day.
- Security level
- This setting determines the maximum number of security doors that can be encountered while drafting in the house. There are three settings:
- Low: Expect to see only 1 or 2 security doors.
- Medium: The default setting. No information about this setting is provided.
- High: Expect to see 5 or 6 security doors. This setting can cause additional security doors to appear in positions where they usually cannot.
- Power
- By default, security doors are powered. While unpowered, the keycard system goes offline and the LEDs on the keycard reader go gray. Attempting to interact with an offline keycard reader, even while holding a Keycard, displays the message "This keycard reader does not appear to be powered on." Changing the offline mode is necessary to benefit out of this setting.
- Offline mode
- This setting determines security doors' behavior while the power has been turned off by the above setting.
- Locked: The default setting. Unpowered security doors can't be interacted with, even with a Keycard.
- Unlocked: Unpowered security doors are automatically unlocked when interacted with.
To summarize the Security and Utility Closet interaction, security doors follow the following system of behavior:
- If the power has not been turned off in the Utility Closet, then security doors act normally, requiring a keycard.
- If the power has been turned off but the offline mode is still set to locked in Security, then security doors refuse entry altogether., even with a Keycard.
- If the power has been turned off and the offline mode has been switched to unlocked in Security, then security doors always allow entry, even without a Keycard.
Drafting from an offline security door results in a slightly different interface from online security doors, with no lights to indicate the floorplans' rarities.
All rooms that can have security doors
Generally, only specific doors in a room can have security doors. Some doors can only be a security door when the security level is set to High.
For T-shaped rooms, the doors are taken from the perspective of the wall that does not have a door (so left means the door that would have an entrance straight ahead and to the left when entered from). For 4-way rooms, the doors are taken from the perspective of the door you enter from (the rooms aren't rotatable)
- The Foundation: The two side doors can be security doors.
- Locker Room: The door can be a security door.
- The Pool: The left door can always be a security door. The right door can be a security door on high security.
- Pump Room: Both doors can be security doors.
- Security: All doors can be security doors.
- Workshop: The door can be a security door.
- Laboratory: Both doors can be security doors.
- Conference Room: The left and forward doors can be a security door.
- Passageway: The right door can always be a security door. The left door can be a security door on high security.
- Commissary: Both doors can be security doors.
- Patio: The north/south door can be a security door.
- Courtyard: The two side doors can be security doors.
- [Upgrade Spoiler: Courtyard] The Corriyard never has security doors.
- Cloister: The forward and left doors can be security doors.
- Archives: The two side doors can be security doors.
- Gymnasium: All doors can be security doors.
- Darkroom: The two side doors can be security doors.
- Weight Room: All doors can be security doors.
[Found Floorplan: Closed Exhibit] All doors are always security doors.
Beyond the Estate
This section contains datamined information about spawning specifics. It may contain spoilers for various stages of the game.
Every day, there is a limit of how many security doors that can spawn, set based on the security level. If more doors than the limit have been spawned, no security doors will spawn. The Closed Exhibit ignores this, and does not contribute toward the limit.
- High Security: Limit 6.
- Normal Security: Limit 4.
- Low Security: Limit 3.
For a door to become a security door, it must pass the following checks:
- Rolling a random float from 0 to 75, this must be greater than the door's (2D euclidean) distance to the center of the Antechamber.
- The size of a room is 10 units.
- If this distance is greater than 60, the door can never be a security door.
- This check is not applied for the Passageway when the security level is High.
- Note that the doors' actual positions are not centered on the doorway (it depends on the room that is spawning the security door), so the chances are slightly different than what a straightforward calculation based on door position would imply. This especially matters for the 60 unit cutoff when drafting from C3 to B3 or D3, as they can sometimes become a security door based on the room (the center of the doorway is 60.2 units away).
If you've found a new clue, you know what to do.
Exactly which doors can be a security door on a horizontal draft from C3?
- The door must be one of the doors that can be a security door.
- If not on high security, there is an additional probability check based on the door.
- The last column of this table, if not N/A, sets the probability of a single non-N/A door to the amount specified, chosen uniformly at random (which may include the door you entered from). If the room being drafted is the first copy of that room in the day, this triggers twice (if it lands on the same door as the first time, nothing happens).
- For the case of The Foundation, this only applies on the day it is drafted; when being retained from a previous day, it only triggers once.
- For descriptions of what the door labels mean, see the #Security doors list. (For L-shaped rooms, they are chosen arbitrarily as the behavior is equal for both doors anyway.)
- Patio: 40% for its north/south door.
- Courtyard: 0% for both doors, but gets hit by the Set increase; this is 60% if it hits left and 70% if it hits right.
- The last column of this table, if not N/A, sets the probability of a single non-N/A door to the amount specified, chosen uniformly at random (which may include the door you entered from). If the room being drafted is the first copy of that room in the day, this triggers twice (if it lands on the same door as the first time, nothing happens).
| Room | Left | Forward | Right | Set |
|---|---|---|---|---|
| The Foundation | 0% | N/A | 0% | 70% |
| Locker Room | N/A | 40% | N/A | N/A |
| The Pool | 0% | N/A | 60% | N/A |
| Pump Room | 70% | N/A | 70% | N/A |
| Security | 0% | 0% | 0% | 70% |
| Workshop | N/A | 50% | N/A | N/A |
| Laboratory | 0% | N/A | 0% | 40% |
| Conference Room | 20% | 20% | N/A | 60% |
| Passageway | 0% | N/A | 30% | N/A |
| Commissary | 0% | N/A | 0% | 40% |
| Cloister | 20% | 50% | N/A | N/A |
| Archives | 60% | N/A | 40% | N/A |
| Gymnasium | 0% | 0% | 0% | 60% |
| Darkroom | 0% | N/A | 0% | 60% |
| Weight Room | 20% | 30% | 20% | 70% |
If all conditions are met, the door becomes a security door.
Interactions
- There is a particular experimental trigger which is activated by unlocking or bypassing security doors. The trigger usually only activates when a security door is opened at the end of the draft, rather than when a security door is unlocked. Drafting into security doors to open them also counts for this trigger.
Unlock effects
Some unique effects exist that can unlock doors without interacting with them. These special unlock effects work on both regular locked doors and security doors. Interacting with the keycard reader of an unlocked security door always results in a draft, even if the door is offline.
- The Foyer causes all doors in all Hallways to be unlocked, regardless of whether they were drafted before or after the Foyer.
- [Studio Addition: The Kennel] After drafting the Kennel, excavating a dig spot or digging for treasure in a room will unlock all doors in that room.
[Outer Room: Shelter] Checking the radiation monitor in the Shelter after triggering an experiment enough times will automatically unlock every door in the house.- [Found Floorplan: Closed Exhibit] If the Closed Exhibit is sheltered at the time that it is drafted, it still spawns with security doors but they are automatically unlocked.
Other kinds of doors
Several other doors exist that can't be opened by any of the usual methods. These doors typically have their own keys or unlock mechanisms and do not interact with anything that interacts with regular doors.
Spoilers Within
This section contains spoilers for the entire game.
Spoilers Ahead
Each box below contains spoilers for the given type of door, including where they are found and how to open them.
Antechamber doors
The Antechamber contains a thick wall in each of its doorways that blocks entry on every side. The doors can be opened by finding levers; see Antechamber#Antechamber Doors for details of where these levers are and alternative ways to open them.
Basement doors
Some entrances to the Basement contain a special door. Interacting with a basement door beings up a screen akin to interacting with a regular locked door, except it says "THE BASEMENT DOOR IS LOCKED", and any normal or special key other than a Basement Key does not fit.
Basement doors unlock permanently once the Basement Key is used on them, not bringing up the locked message for that door ever again.
Basement doors can be found in the following locations:
- The Grounds, at the bottom of the Fountain once it has been drained using the Pump Room, connecting to Abandoned Mine
- The Foundation, on the bottom floor after taking the room's elevator, connecting to Basement
- [Lategame location] Crate Tunnel, as the second door in the sequence
Sanctum doors
The Inner Sanctum contains a chamber with eight doors. These doors can be interacted with if you have a Sanctum Key, which gives a prompt to permanently unlock the door using the key.
Red doors
In The Underpass, a side tunnel contains a red door. This door can be unlocked by sending steam power to the red box in a currently drafted Boiler Room, then going to the red box next to the door and pressing the button. Once this is done, the door remains unlocked permanently and can be opened even when a Boiler Room has its power diverted away from the box or is not drafted.
- [Lategame location] The Crate Tunnel also contains a red door, as the 5th door in the sequence.
Microchip doors
In Blackbridge Grotto, there is a big door that can only be opened by placing all three Microchips into the receptacle in the center of the room. The door is only open while the Microchips are placed, and closes a few seconds after one is removed.
- [Lategame location] The Crate Tunnel also contains a microchip door, as the 7th door in the sequence.
Blue doors
The 8th door of the Crate Tunnel is a large blue door with a Mt. Holly logo on it. This door can be opened using the ability of the Throne of the Blue Prince; drafting 8 rooms in a row after the Throne of the Blue Prince causes the blue doors to become permanently unsealed, after which it opens by walking up to it.
- [Lategame location] There is also a blue door found at the entrance to the Atelier.
Certain interpretations of "door" may result in several other walls being classified as a "door", most notably certain locations that require the use of a Contraption to pass, but they are never actually called doors.
Additional information
- A red memo in the Hallway falsely claims that doors in the West Wing are more likely to be locked. In reality, each wing is equally likely to contain locked doors.
- A blue memo in Security reveals that both locked doors and security doors become more frequent with higher rank.
- [Mail Room Experiment Spoiler] Security doors are the topic of Randolph's seventh letter to the Mail Room. In the letter, Randolph explains that they were installed two years ago after a certain staff member breaking into a room that they should not have been able to access, and that the more trusted staff members were given keycards to access them. He also explains the Keycard System settings in Security and mentions its unlocking synergy with the Utility Closet.
