Shops let players buy and sell goods for coin. A shop is just a mobile marked as a shopkeeper, so everything in All about Mobiles applies to it too. Money is the usual gold / silver / copper — 1 gold = 100 silver, 1 silver = 100 copper.

A shopkeeper sells the items it holds (each at its value) and buys sellable items from players (at a discount — its rate). The coins it pays out come from its own till, so a shop can run short of money until it earns more.

A shopkeeper is a mobile with data shopkeeper true. Make it npc as well, so it can't be dragged into a fight:

mob create grocer
mob grocer data shopkeeper true
mob grocer data npc true

An item is worth whatever its value says, written in coins. Anything with no value (or a value of zero) can't be bought or sold.

• item ref data value 5 copper — five copper
• item ref data value 1 silver 5 copper — mixed coins (gold, silver, copper)

To put goods on the shelves, give the shopkeeper items you've priced — giving is just a plain hand-over, so the item drops straight into the shop, for sale. By default an item is one of a kind: once a player buys it, it's gone. Mark an item data stock true and the shop never runs out of it (each sale hands the buyer a fresh copy):

item create torch
item torch data value 5 copper
item torch data stock true
give torch grocer

The grocer now sells torches forever. (A shop also re-sells items players bring in — see below — but those are finite and vanish once bought.)

A shop buys items players sell it, then re-sells them at full value. Two fields control the buying side:

• data rate percent — how much of an item's value the shop pays, default 50.

mob grocer data rate 40 pays 40%.

• data gold / silver / copper — the shop's till. Seed it so the shop has coin

to pay with: mob grocer data gold 20. When the till is empty the shop can't buy

until it earns more (players buying from it top it up).

A shop won't buy junk, cursed, donated or garbage goods (the sort that pile up in the recycling and the dump), nor anything with no value.

These work whenever a shopkeeper is in the room:

• list — what the shop sells, with prices (an endless line reads (in stock))
• value item — ask the shopkeeper what they'd give you for it (their offer)
• buy item or buy n item — buy at full value (buy 5 arrows)
• sell item or sell n item — sell at the shop's rate
• sell all [keyword] — offer each carried item in turn; answer y, n, or q to quit

mob create blacksmith
mob blacksmith data shopkeeper true
mob blacksmith data npc true
mob blacksmith data rate 40
mob blacksmith data gold 25
item create dagger
item dagger data value 2 silver
item dagger data stock true
give dagger blacksmith

The blacksmith now sells daggers (2 silver each, never out of stock) and buys blades adventurers bring in at 40% of their value, paying from a 25-gold till.

• All about Mobiles — making and configuring the shopkeeper itself
• All about Items — creating, describing and pricing items
• In-game: help item, help mob