# fen.flora The growing and drowning parts of Yowe Fen: reed beds (chunked into bands along the run so the far end culls away), peat hags, the drift of broken timber standing out of the water, the water plane itself, and the horizontal fog banks that lie over it. Reeds are sampled with a hard bias toward the causeway — a uniform spread over a ninety-metre fen puts almost nothing in the two bands the camera actually looks along, and reads as stubble rather than as a bed. The fog banks are strips whose alpha rises from nothing at both ends: a sheet with a hard edge, seen nearly edge-on, projects as a wedge with two straight borders across the frame and reads as a plate rather than as fog.

# fen.build The made things of Yowe Fen: the rotted causeway and its piles, the five stage-posts a hernsew stands on, the Low Staithe behind you and the High Fold ahead, the sluice, and the eel gear the length of the run. Each builder takes a `Parts` table and accumulates into it by material name, so the whole of the fen's timber arrives as one mesh, its stone as another, and so on. `fen.marsh` uploads them. Positions come from `game.rules` — the stations, the deck width, the fen's length — so the causeway and the herons standing on it describe the same place.

# rules <!-- zero:scaffolded-readme --> <!-- Replace the line below with what this module provides and who consumes it, then delete both comment lines. --> TODO: describe this module.

# fen.geom A small mesh builder. The fen is five hundred deck planks, eighty piles and forty thousand reed blades, so it is accumulated into flat vertex streams here and uploaded as a handful of merged runtime meshes rather than being an entity per plank. Every vertex carries a colour, and the `pbr` shader multiplies base colour by it — that is what carries the weathering (a plank's sodden end, the pale crown of a reed, the tar at a pile's waterline) with no textures at all. ```lua local Geom = require("fen.geom") local b = Geom.builder() Geom.box(b, centre, half, colour, { up = …, topColor = …, topScale = … }) Geom.prism(b, base, axis, r0, r1, sides, colBottom, colTop, capBottom) Geom.blade(b, root, height, width, leanX, leanZ, yaw, colRoot, colTip, segments) local mesh = Geom.upload(b) -- a MeshHandle a Model can wear ``` `Geom.rng(seed)` is a deterministic little PRNG: the fen has to come up the same every boot, on every machine, or it is not a place. `half` is a HALF-extent. Writing a length there gives you a shape twice the size you meant, which at this game's grazing camera angle is the difference between a floating plank and a dark shard across the frame.