# HL The shared spine of *Helsinki Life*: constants, the board graph (43 tiles with positions, kinds, districts and successors), landmark anchors, camera framing numbers, the game state container, the event bus the slices talk over, the `HL.actions` table the rules fill in, the pacing (`HL.TIMING`) and the sound names (`HL.SFX`). ```lua local HL = require("game.core.HL") HL.tile(6).next -- { 7, 101 }: the fork at Pasila station HL.pawnSlot(22, 2) -- where pawn 2 stands on the Cathedral tile HL.on("moveStep", function(ev) ... end) HL.emit("sfx", { name = "hop" }) HL.state().players[1].money ```

# wheel The physical spinner of **Helsinki Life**: a brass-cased ten-sector dial that appears beside the tram whose turn it is, turns while the spin runs, and eases to a stop with the spun number under its pointer. ```luau local Wheel = require("game.pieces.wheel") local dial = Wheel.spawn(parent, "spinner") dial:place({ x, y, z }, aspect) -- beside the active tram dial:startSpin() -- on HL "spinStart" dial:land(value) -- on HL "spinResult" dial:update(dt) -- returns "tick" | "stop" | nil ``` The sectors alternate cream and HKL green with the ten in sun yellow, and each carries its number in whichever of the two inks its own sector is not, so the value the log reports is legible on the model itself. The dial is tilted toward the camera so a tall frame reads the face, and the pointer stands at the root's own `-Z` - the far, up-screen side of a board the camera looks north across. `Wheel.yawFor(value)` is the hub yaw that puts a sector under the pointer and `Wheel.valueAt(yaw)` is its inverse, so what the dial shows can be read back and checked against what the rules reported. Timing is its own: the dial turns freely for at least `MIN_FREE_SECONDS` before it eases, so a caller that reports its value the instant it is asked still gets a spin somebody can watch. After `HOLD_SECONDS` on the landed value it shrinks away rather than being left behind on the board.

# meshkit A small flat-shaded mesh builder - the geometry the **Helsinki Life** pieces are modelled with. Every triangle carries its own face normal, which is what gives the low-poly diorama its crisp shaded facets. ```luau local kit = require("game.pieces.meshkit") local b = kit.builder() b:extrudeX(profile, halfWidth) -- a closed { z, y } profile swept across X b:wedge(radius, halfAngle, thickness, segments) b:ring(inner, outer, thickness, segments) b:tri(p0, p1, p2, facing) -- facing states which way the face points b:quad(a, b, c, d, facing) b:polygon(points, facing) local mesh = renderer.mesh.create(b:build(), guid) ``` A face states the direction it wants to point and the builder orders the triangle to match, so geometry is written by shape rather than by winding; `extrudeX` takes its profile in either direction and orients every wall outward from the profile's own centroid. `kit.yawQuat(deg)` and `kit.pitchYawQuat(pitch, yaw)` build the `{x, y, z, w}` rotations the pieces are posed with. `builder:triangleCount()` is the cheap check that a shape actually produced geometry.

# tram The player pawn of **Helsinki Life**: a toy HKL tram, modelled once as a runtime mesh and stood up per player with that player's colour on its paintwork. ```luau local Tram = require("game.pieces.tram") local pawn = Tram.spawn(parent, 1, "pawn_green") pawn:setPose({ x, y, z }, yawDegrees, leanDegrees) pawn:setVisible(false) pawn:despawn() ``` The hull is a side profile - raked nose, domed roof, waist band - extruded across the width by `game.pieces.meshkit`. On top of it sits the detail that makes it read as a made thing: a three-pane window strip per side with doors between, a recessed raked windscreen and rear window, the cream band carried round both ends, bogies and bumpers, headlamps and tail lamps that glow, a trolley pole with its contact bow, and the route number on the nose board and both flanks. The four seats carry real Helsinki lines - 3, 6, 9, 1. Forward is the entity's own `-Z`, so a pawn travelling south down the board stands at yaw 180 and shows its face to the player. `M.SCALE` is the size the model is stood on the board at, chosen so four pawns sharing one tile at `HL.pawnSlot` - 1.1 board units apart - stand clear of each other. Finishes come from `game/pieces/materials/`: `piece_paint` (tinted per player), `piece_cream`, `piece_glass`, `piece_metal`, `piece_lamp`, `piece_tail`.