You are a shopkeeper @. You spend the game puttering about in your shop. Adventurers come in and sell you things, you sell them supplies. The objective is to get 1 million GP and retire.
The shop is a little 10x10 room with a door. You can lay out items on the floor. After a few turns an adventurer comes in. He wanders round randomly. He likes to go near items which are pleasing to him and avoid crap items. If he steps on something he likes he'll haggle for it. If he finds an open space he'll start dropping treasure items onto it and haggling to sell them to you.
Adventurers have names and stats (you could hijack the Angband character generation code). You like to see adventurers with low Wisdom (bad hagglers) and high Strength (can carry lots of stuff away with them).
Sometimes adventurers of opposite alignment will attack each other. (Especially if you encourage them - hand the Elven Paladin a potion of berserk rage just as the Half-orc rogue wanders in?). Not so bad for you as you get to loot the corpse. Sometimes they attack you! (Very simple combat system.) Sometimes they try to steal your stuff and run out.
As you get further in the game, more and more adventurers come in at once and try to talk to you and it gets more and more confusing and junk builds up and you run out of good stuff to sell and it all gets a bit frantic!