8 steps

Inventory, crafting and shops

For: Games where players collect, combine and trade things.

Items are the part of a game most likely to end in a duplication bug or a bag that cannot be trusted. Build the container first and make it strict, then everything that moves items through it.

The steps, in order

1
Blueprint
Inventory System
A place for what the player carries, with limits that force choices and rules that never lose or copy an item.
Why here: The container, with one rule above all: an item is in exactly one place. Every later step depends on this being true.
2
Blueprint
Item Stacking
Stack limits turn a bag into a set of choices: small piles for rare things, big piles for common things, and a clear answer every time an item arrives and there is not enough room.
Why here: Stacks are where counts go wrong: splitting, merging, and a stack size that changes with an update.
3
Blueprint
Weight Limit
Weight makes carrying a choice without a fixed number of slots. The player can take one more thing and move slower, or leave something behind, and the cost is easy to feel and easy to read.
Why here: A limit gives choices meaning. Weight or slots, pick one, and decide early what happens at the limit, because every pickup will ask.
4
Blueprint
Equipment Slots
Slots turn a pile of gear into a set of choices: one helmet, one weapon, a pair of rings. The player decides what to wear, and the game always knows what is worn and where everything else is.
Why here: Equipping is moving an item between two containers with rules. Treat it that way and swaps never lose anything.
5
Blueprint
Crafting System
Crafting gives the things players gather a use, and lets them decide what to make from what they have.
Why here: Crafting consumes and produces in one step, or not at all. The half-done craft is the classic duplication bug.
6
Blueprint
Recipe Discovery
A recipe the player found by experimenting feels like an earned discovery, and a hint after a run of misses keeps a stuck player from giving up or opening a guide.
Why here: What a player may craft is a question of knowledge, kept apart from what they can craft right now.
7
Blueprint
Currency Wallet
A wallet turns effort into choices. The player earns coins, weighs what to buy, and feels the cost of each choice, so shops, rewards and prices all have a number to work with.
Why here: Money is an item with its own rules: never negative, never fractional, never silently capped.
8
Blueprint
Shop (Buy and Sell)
A shop turns coins into things the player wants and things the player no longer needs back into coins, without ever letting the player print money.
Why here: Shops come last because they are crafting with money: one exchange, checked on both sides, or nothing happens.

At the end

Items can never be lost or doubled, crafting and shops move them through one set of rules, and the player always knows what they carry.

What this rests on

Talks, articles and research from outside this wiki, so you are not taking our word for it.

Economic Balancing and Improved Monetization Through Clever Sink Design (Vili Lehdonvirta, Oxford Internet Institute, GDC 2014 Free to Play Summit, 2014)
Explains the ways a game can take money and items back out of play (sinks), and why players accept some of them more readily than others, so prices do not spiral.
How CD Projekt Red made crafting work with Witcher 3's dynamic economy (Alex Wawro, Game Developer (reporting on Matthew Steinke's GDC Europe talk), 2015)
Shows how one price value per item, shops that buy low and sell high, wearing-out gear and zero-weight crafting materials keep crafting, money and carrying limits in balance.
Never Enough Space! Redesigning the inventory system for Unexplored 2 (Joris Dormans, Game Developer (Featured Blog), 2022)
Shows why a hard slot limit frustrated players and how a softer weight-like limit with penalties moved the hard choice to a calmer moment.
7 crafting systems game designers should study (Bryant Francis, Game Developer, 2015)
Compares crafting in seven well-known games to show how scarce materials, professions and recipes shape tension, player economies and experimentation.
Virtual Economies: Design and Analysis (Vili Lehdonvirta and Edward Castronova, MIT Press (book page at Oxford Internet Institute), 2014)
A book that applies basic economics (supply and demand, money, markets, pricing) to game items and currencies, explaining why economies inflate or stay healthy.

Say this to your AI

Follow the Spielerando learning path "Inventory, crafting and shops" (get_path inventory-crafting-and-shops) for my game, step by step, and tell me at each step why it comes now.

Or skip this and connect the MCP: your AI then finds all of this by itself.Connect the MCP