Simulation Mode

Simulation Mode is the central mechanic of the PRISM Project and the means by which the player experiences the world of Rockvil. It is not a game-within-a-game in the traditional sense — it is the Project’s raison d’être. PRISM, a sentient computer, enters a detailed simulation of a future South Dakota town to forecast the long-term consequences of the “Plan for Renewed National Purpose.” The player embodies PRISM who, in turn, embodies “Perry Simm” — a simulated everyman living through five decades of societal decline.

Entering the Simulation

From Comm Mode’s control center, the player commands PRISM to enter Simulation Mode. The transition is guarded by SIMULATION-CHECK in prism.zil: if already simulating, it blocks redundant entry; if not, it allows passage. Perelman’s staff grows increasingly impatient when PRISM delays. In message M (prism.zil lines 95-122), an exasperated Perelman warns: “PRISM, what’s the matter? You haven’t started the simulation yet! For heaven’s sake, don’t you know the whole country’s impatient? Vera is hopping mad — if you don’t begin soon, I can’t tell what’s going to happen!” This is not merely flavor text — Vera is PRISM’s political sponsor, and her impatience hints at the external pressures that will later destroy the Project.

The SIM-LEVEL-TABLE is reset when message C arrives, enabling entry. The SIMULATING global is set true, and the game world shifts from the sterile interface rooms of 2031 to the lived-in spaces of Rockvil.

Five Decades, One World

Simulation Mode spans five target years, each a decade apart: 2041, 2051, 2061, 2071, and 2081. These are not separate scenarios but the same world at different points in time. Locations persist across decades — the Simm apartment at Parkview, Dunbar’s department store, City Hall, Main & Kennedy — but their descriptions, inhabitants, and conditions change radically.

The SYEAR global tracks the current simulation year, and nearly every room description, object interaction, and character routine branches on it. This is the game’s structural genius: a relatively compact set of rooms (~100 locations) produces an enormous sense of scope because the player returns to the same places and witnesses their deterioration.

Verisimilitude: Day/Night, Weather, Routines

The simulation is not a static diorama. The LIGHT-LEVEL global (0-3) tracks the transition from night through dawn to full day and back to dusk, driven by the I-SUNRISE-SUNSET interrupt in interrupts.zil. The sky’s appearance when examined branches on SIMULATING in globals.zil (SKY-F): in the early decades, skies are “light”; by 2061 and 2071, they are “gray and smoggy” (scoring 2 points).

Characters have daily routines that unfold stochastically. Jill’s day in 2041-2051 follows a 12-state counter: waking, dressing, making salad, painting, reading, doing her hair, going to bed. Mitchell’s school schedule in 2051 is equally detailed: waking, dashing off to school, returning to play logic games, doing homework. These routines make the simulation feel inhabited.

Weather, though not explicitly described in most outdoor locations, is implied through seasonal daylight variation and detail text about “chilly” air and “acidic rain.”

The Elevator and the Stairs

A small but telling detail: INNER-LOBBY-ENTER-F in apartment.zil (lines 282-322) determines whether Perry takes the elevator or walks up. In 2041 and 2051, he takes the elevator. In 2061 and 2071, the elevators are “out as usual” (score item 3, 1 point), and Perry must slowly climb several flights. By 2071, the cracked glass of the lobby door is “held together by boards” (globals.zil, UNOPENABLE-DOOR-F). This single routine illustrates how the simulation embeds societal decay in mundane infrastructure failures.

The Player’s Relationship to the Simulation

Critically, PRISM does not merely observe the simulation — PRISM inhabits it as Perry Simm. The player can walk Rockvil’s streets, talk to Jill, buy clothes, watch films, read newspapers, and be arrested, beaten, or killed. This embodied perspective is what makes the game’s political argument effective: you are not reading about decline, you are experiencing it from inside a body that ages, weakens, and suffers alongside the world.

The simulation can be aborted back to Comm Mode at any time — a safety valve that underscores PRISM’s dual nature as both participant and observer.

Thematic Weight

Simulation Mode is the Project’s purpose, but it is also the game’s thesis: that a society’s future is knowable if you simulate its trends honestly. The tragedy is that the people who commissioned the simulation do not want to see what it reveals. The Plan for Renewed National Purpose produces a surveillance state, a theocratic dictatorship, and ecological collapse — and the simulation documents every step of it.

See Also

• recording — How PRISM documents observations during Simulation Mode
• interface-mode — Comm Mode and Library Mode, the other two modes of PRISM’s existence
• the-project — The PRISM Project, its staff, and its political context
• rockvil-across-decades — How the city transforms across the five simulation years