D4
- Template
- Place
- Status
- Canon
- Kind
- Level
- Parent
- Military Base
1. Summary
D4 — Artificial Intelligence and Robotics Level.
D4 once housed artificial-intelligence research, robotics development, robotic security systems, and a sophisticated center for geopolitical prediction and information analysis. Today it contains derelict machinery, Flesh Nests, unpredictable surviving scientists, and armed patrol robots.
2. History
Construction of Level D4 began on March 16, 1962, under joint Brazilian-American administration, and the level became operational on October 21, 1966. Dedicated to artificial intelligence, robotics, advanced computing, and automation, D4 became one of the facility's most energy-intensive research divisions. Its scientists developed experimental hybrid computers combining digital and analog processing, sophisticated neural networks, early quantum computing experiments, and the technology known as Analog Brains. What these breakthroughs made possible: See: Artifacts and Technology › Analog Brains And Hybrid Computers.
3. Function and Contents
One of D4's most ambitious projects involved large-scale geopolitical prediction. Using enormous computing systems, international news feeds, intelligence reports, and mathematical models, researchers attempted to anticipate political events, military conflicts, economic crises, and individual human behavior. Historical predictions were evaluated against actual outcomes, with successful forecasts marked in green and failures in red. Some projections extended as far as the year 2552. These experiments generated profound philosophical debates about determinism, free will, consciousness, and the ethical implications of acting upon predicted human behavior.
D4 also houses Amanda, an advanced stationary artificial intelligence developed through the Analog Brain program within the facility's hybrid computing research. The protagonist can reactivate Amanda and communicate with her directly through speakers installed in her computer chamber. She can explain aspects of the facility's history, its scientific discoveries, and the autonomous machines operating throughout the complex. D4 remained operational until the 1999 catastrophe, after which its automated maintenance systems continued preserving much of its infrastructure. During exploration, the player encounters surveillance systems, armed patrol robots that engage detected intruders with machine guns, surviving scientists (the Broken Survivors) and Flesh Nests; the heavily armored robotic soldiers developed here guard D5's approach toward D6. The approach to the elevator toward D5 lies wrecked by an earlier battle. An optional mission involving Amanda allows the player to disable certain lethal robotic security systems.
Cancer Dogs and Roach Rats are confined to D3 for now; they do not appear as normal D4 enemies.
See: Characters › Amanda
See: Enemies › Broken Survivor
See: Enemies › Flesh Nest
See: Enemies › SQUAD Unit
3.1 Electrical Distribution
After the fusion reactor in D3 restarts, D4 is still completely dark.
Electricity is arriving from the reactor, but damage within D4's distribution network prevents it from reaching the sector. The repair runs through three electrical repair checkpoints, where the local connections are restored or rerouted.
If the reactor is stabilized, most connected areas of the facility receive steady power.
How the restored current behaves before and after stabilization is part of Chapter Seven's main quest and of the reactor's description.
See: Artifacts and Technology › Fusion Reactor
3.2 The Occupied Research Office
Behind a laboratory door in an occupied research office, a surviving scientist works feverishly among broken computers and stacks of papers. He worked on portal research.
An adjoining room is unexpectedly preserved and decorated with Buddhist art, inscriptions, and meditation materials. It also holds survival supplies the scientist accumulated: bandages, medicine, ammunition, and a pistol.
The side quest The Last Shift starts and ends here.
See: Campaign › 7. A Question Of Trust
See: In-World Documents › Portal Transit Research Assessment
3.3 Geopolitical Prediction and Intelligence Section
An intelligence department analyzed international reports, historical data, social behavior, and mathematical models to forecast wars, political crises, economic upheavals, and other world events. Its archive includes remarkable predictions, mistakes, and projections reaching toward 2552. Among the records is Amanda's warning of February 1999.
See: In-World Documents › Amanda's February 1999 Warning
Other records concern Amanda's skill in memetic control and information engineering.
See: Characters › Amanda
The side quest False Alarm takes place here, and its use of the section's communications equipment is part of the quest.
3.4 Inhabitants and Intended Player Experience
The two D4 enemy types represent contrasting forms of danger:
Patrol Robots are systematic, predictable, and militarily dangerous. Broken Survivors are emotionally unstable, unpredictable, and dangerous precisely because they do not behave like trained combatants.
Neither enemy type should operate as a conventional video-game enemy that automatically attacks whenever the player enters a fixed detection radius.
The objective is to make D4 feel like an abandoned research installation in which two radically different forms of danger coexist.
D4 should not feel populated by conventional enemies waiting to be defeated. It should feel inhabited by the surviving machinery and broken people of a catastrophe whose consequences have never ended.
4. Architecture and Style
D4 represents a major architectural evolution from the earlier underground levels, combining American Cold War military construction with the technological aesthetics of 1960s computer research centers. Its design features wide geometric corridors, reinforced concrete structures, smooth metallic wall panels, automated security doors, observation windows, and extensive electrical infrastructure. Interior finishes emphasize off-white, pale gray, desaturated green, and blue-gray tones, complemented by dark metallic equipment and cold fluorescent lighting. Large computer chambers contain towering mainframes, analog computing modules, magnetic tape systems, control consoles, and extensive cooling installations.
Due to its extraordinary electrical and mechanical requirements, D4 incorporates large power distribution facilities, technical floors, cable passages, ventilation shafts, cooling systems, and dedicated maintenance corridors. Industrial elevators, cargo platforms, and internal transport connections support the movement of personnel, machinery, and heavy equipment. Its original 1960s architecture remains recognizable beneath decades of technological upgrades, with later computing equipment and robotic infrastructure integrated into the existing structures.
Unlike D1, D2, and D3, D4 remains remarkably well preserved due to continuous robotic maintenance. Its corridors are predominantly clean, its lighting and machinery are intact, but its internal power distribution was damaged, so the level stays dark even after the fusion reactor restarts until that distribution is repaired; its robots and much of its machinery continue operating autonomously on the base's experimental battery system. Minor signs of aging, obsolete equipment, occasional damaged surfaces, and areas abandoned after 1999 reveal the facility's age. The overall atmosphere should resemble a massive underground Cold War computing and robotics research center, continuously modernized through 1999, where aging technological infrastructure coexists with extraordinarily advanced autonomous machines.
5. Security and Access
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5.1 Robotic-Security Control Room
A control room in D4 was used to administer the robotic patrol network.
The side quest Ghost Protocol takes place here, and the state in which Edmund finds the room is part of the quest.
6. Connections
The elevators that lead from D3 to D4 cannot operate without the fusion system.
See: Places › D3
6.1 The Elevator Toward D5
The approach to the elevator leading onward toward D5 has been wrecked during an earlier battle. How Edmund reopens it is part of Chapter Seven's main quest.
Without the reactor the elevator toward D5 cannot run; D5 is then reached by a parallel route, harder than the elevator.
See: Places › D5
7. Concept Image
D4 — Artificial Intelligence and Robotics Level concept, kept in the game repository at environments/military_base/children/d4/concept.png
8. Open Questions
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