Every gallery before this one was about the things in a world. This one is about the world itself — procedural generation, which is the plain idea that a place can be arithmetic: a handful of rules and one starting number, and the map draws itself. Thirteen generators in three families. Scatter & noise: points that keep their distance (Poisson-disc), a side-view ground from layered noise with biomes by height, regions by nearest seed (Voronoi), and trees from a rewrite rule (L-systems). Rooms, caves & mazes: caves grown by a neighbour rule (cellular automata), rooms carved by halving (BSP), mazes with two personalities (recursive backtracker vs Prim's), tiles chosen by constraint (wave function collapse, the small tiled kind), and tiles picked by a bitmask (autotiling). Dice, waves & saves: weighted loot tables and fair shuffle bags with a pity timer, a spawn director's wave curve, the world folded into a JSON save that survives its own old versions — and the one card the whole book has been promising since its glossary: a seed. Every generator here takes a seed dial and draws from rng(seed), so the same seed makes the same world on every machine; the last card shows two panels agreeing and a third disagreeing by exactly one.
Each card grows on screen — you watch the passes, the splits, the collapses — then rests, then regrows with the next seed; click a running card to regenerate, place a goal, paint a wall, or roll the dice (a small badge says click or drag until you have). Press ▶ Run all, or wake one at a time; the tempo buttons run everything faster for skimming. Every generator also hides a rhyme — the same rules with two or three dials turned (a stricter neighbour rule turns caverns into catacombs; Prim's instead of the backtracker turns a labyrinth into a thicket) — click ⇄ its rhyme to swap them in place, and open code to read the pair: every card keeps its numbers in a D = { … } block at the top. Chapter 19 is the encyclopaedia entry: each generator in plain words, when to reach for which, and the four engines' spellings.
Every generator is one function, make(u), returning { frame(dt, t), press(x, y) }. Its dials sit at the top in a D = { … } object — the seed is always among them. The kit u is the locomotion lexicon's kit (stage(), mote(), dot / ring / line / rect / poly / arrow / label, rand / rng(seed) / noise) plus the world tools: noise2(x, y) (two-dimensional value noise), cells(cols, rows) (a grid with safe get/set), drawCells(grid, x, y, cw, ch, colourOf), shuffle(arr, rng), and the colour helpers mix, shade, rgba, hsl.
The preview is bigger than the cards; every generator is written relative to W and H. Click the preview to trigger the press reaction.
seed and run it twice — identical both times; that is the whole promise. In Caves, set rule to 4 and the caverns open up, 6 and they close into tunnels; in Maze, swap algo; in Poisson, halve r and watch the count quadruple; in Wfc, remove one line of the rule table and the lakes lose their shores; in Save, delete a field from the old-version save and watch the migration fill it back in. A world is a rule, a neighbourhood, and a seed.In Godot: all 13 (+13 rhymes) are ported — three family files in scenes/world/, paged in worlds.gd (grab the Godot project and press its menu's Z; right-click for the rhyme, double-click to enlarge). Godot also ships the packaged spellings — FastNoiseLite, TileMapLayer terrain sets (autotiling with no code), AStarGrid2D, RandomNumberGenerator.seed, FileAccess + JSON for saves — and the chapter names each beside the hand-rolled version. In Unity and Unreal: Mathf.PerlinNoise / Random.InitState(seed) / JsonUtility and Rule Tiles; PCG framework, FMath::PerlinNoise2D, FRandomStream(seed), SaveGame objects — chapter 19 and its cheatsheet carry the table.