Architecture of “Skhodka”: C4 and critical paths

“Skhodka” is a Saturday evening of an IT community in a Batumi bar, 19:00 → 01:00, about 18 minutes: browser only, no server and no build step, three.js ships alongside. This is how it is put together: C4 diagrams down to components and the four paths everything rests on.

C4: context and containers

Level 1. The system and its surroundings

Level 2. Containers

C4 level 3: components of each context

All parts are plain scripts with an L registry: L.def declares a part, L.use fetches it and runs it on first use. A dependency cycle fails at once with a clear error. Contexts talk through the world’s event bus (world.bus) and the world.act call.

Simulation

• World holds the clock (180 real seconds per game hour), the people, the player, the seats and the event bus; outward it exposes step, act, view.
• Crowd builds guests from roles, minds and needs and fits the arrival schedule to the evening curve by an invariant, not by tuning.
• Brain decides for the guests: seat, bar, smoking area, conversation groups. Director starts events and phone messages.
• Talk plays out the reply cards; Score counts acquaintances, pairs, the photo and the title.

Hall and people

• Scene builds SushiGO from the plan and decor, 2–4 real lights, the rest of the light baked into textures; effects: rain, sax, karaoke and more.
• Quality switches low / mid / high by frame rate: down fast, up slowly, never above a rung it already failed on.
• People: each person is a single SkinnedMesh, animation is procedural from pose, mood and “is speaking”.

UI

• Ui subscribes to world events (talk:line, ladder, pair, chat, toast, end) and sends the player’s actions to world.act.
• Its own ui.bus: pause, quality, sound, “another Saturday”.

Four critical paths

1. Startup and a new evening

2. A simulation step

3. A player’s reply and its consequences

4. A frame

The rules everything rests on

• The simulation knows nothing about the screen. No DOM, no THREE: it is seen only through view() and the event bus.
• Content is data. The engine receives CONTENT whole; stories and numbers change without the engine, numbers are overridden by TUNING.
• One seed, one evening. A seeded random generator and a fixed step give repeatability.
• Invariant instead of tuning. The head count at peak hours is fitted into a corridor by a formula.
• The weak machine comes first. Quality adapts to frames, light is mostly baked.

Weak spots