Crafting — Recipes & Combinatorial Depth

What it is. A recipe system: inputs (materials, items, ingredients) combine by rule into outputs. The depth is combinatorial — a modest set of inputs and recipes yields a large possibility space. The design choice is how the player learns the space: handed the recipe (lookup) or finding it (discovery).

Player fantasy / why it’s fun. “I turned these scraps into that.” Crafting rewards planning and packrat instinct; discovery crafting adds the “what if I combine…” curiosity. The pull is the recipe you don’t have yet — and the hunch about what makes it.

When to use / when NOT

Use it when	Skip it when
Combining things is a core verb (survival, sim, alchemy)	Items are found whole; no combination step
You want depth from few pieces via combinatorics	A flat shop (`system-economy`) covers acquisition
Recipe discovery can carry curiosity	Recipes would just be an inventory tax

Crafting is the convert node of a system-resource-loops made combinatorial. If there’s exactly one useful recipe per material, you don’t have crafting — you have a conversion. Crafting earns its name when choices between recipes exist.

Variants

Variant	How the player learns	Depth from	Example
Recipe list (lookup)	Given the recipe book	Resource management	Minecraft (known), Stardew
Discovery	Experiment to find combos	Curiosity, “what if”	Little Alchemy; Doodle God
Grid/shape	Spatial arrangement matters	Pattern puzzles	Minecraft crafting grid
Modifier/affix	Base + modifiers roll	Build optimization	Diablo runewords; PoE crafting
Emergent (systemic)	Rules interact, no explicit recipes	Second-order surprise	Breath of the Wild elixirs; Noita

The discovery and emergent variants trade legibility for wonder — powerful, but they need a fallback so the player is never stuck (a hint, a partial reveal).

Tuning levers

Lever	What it controls	Healthy range / rule
Recipe count	Breadth of the space	Enough to explore; each recipe must do something distinct
Combinatorial fan-out	Outputs per input set	High fan-out = deep from few pieces (the whole point)
Discovery vs lookup	How recipes are learned	Discovery for wonder; lookup for planning games. Mixing: teach basics, hide the exotic
Ingredient scarcity	Cost of a craft	Ties crafting to the economy — scarce inputs make recipes decisions
Legibility	Can the player plan?	Show what a recipe needs before they commit ingredients
Dead-end density	Useless recipes	Keep low — a discovered recipe that does nothing punishes curiosity

How it wires to Hayao

Recipes are pure data + pure logic. A recipe is {inputs, output}; crafting is a pure function over inventory state in world.state, invoked by an input action. This makes the recipe space machine-checkable: it’s the same shape as a Puzzle<State, Move> — you can solver-search “is item X craftable from starting materials?” the way the grid-puzzle solver proves reachability ([[FUN.md §1]]).
Prove reachability. Assert every intended output is craftable from obtainable inputs — a connectivity proof over the recipe graph, mirroring the roguelike “all loot reachable” sweep ([[FUN.md §10]]). No orphan recipes.
The crafting UI is chrome. The recipe book / bench menu is showScreen() DOM; inventory counts are sim state, the panel is cosmetic (CLAUDE.md invariant 4, [[FUN.md law 6]]).
Generate the recipe set as content. Lean on src/content/ to generate balanced recipe trees and prove them reachable, rather than hand-authoring a hundred recipes and hoping.

Fails when…

Orphan recipes. An output nothing reaches, or an ingredient nothing uses — dead weight. Prove the graph connected.
One true recipe. If every craft has a single obvious answer, it’s conversion cosplaying as crafting. Add meaningful alternatives.
Discovery with no floor. Pure discovery + no hints = players stuck, guessing. Always give a nudge before frustration.
Illegible cost. Committing ingredients before seeing the recipe wastes scarce materials — feels like a trap.
Inventory tax. Crafting that’s mandatory busywork (craft to progress, no choice) — cut it or make it optional.

Verify

Recipe reachability as a connectivity/solver proof (every intended output craftable): [[FUN.md §10]] (connectivity) and [[FUN.md §1]] (solver over a Puzzle-shaped state).
Determinism: same inputs → same output, replay-hash identical: [[FUN.md law 7]].
Ingredient economy stays in a pacing window: [[FUN.md §14]].

Composes with

system-resource-loops — crafting is the combinatorial convert step.
system-economy — ingredients are currency; recipes are structured sinks.
system-build-diversity — modifier/affix crafting is a build engine.
system-collectibles — a recipe book is a set to complete.
system-tech-tree — research unlocks new recipes.