In your first puzzle, one person wanted the pencil. The pencil’s owner wanted a book. A spoon did not meet that want, so the proposed exchange could stop.

Barter means directly exchanging goods or services without money. Both people need to accept the exchange. Having something to offer is not enough if the other person does not want it.

Try changing just one want. Suppose the pencil’s owner now wants the spoon. A direct swap can work. The objects did not change; the match between wants did. A third person with a book might offer another possibility, but the agreement would become more complicated.

Money can help people pay without finding that exact pair of matching wants. Your game lets you feel one difficulty of direct exchange. It does not show how every real community traded or how money first appeared. Keep the problem you tested separate from the larger historical question.

Coins and bills are familiar forms of money. They are not the only objects people have used for exchange. The Smithsonian records a cowrie shell from Asia in its money collection. Cowries were used as money in parts of Asia.

That example broadens your first puzzle. A shell could be useful in exchange where people accepted it for that purpose. It does not mean every shell everywhere was money. The place and the accepted use matter.

In your game, a spoon became useful when a partner wanted it. An accepted payment object has a different role: a seller may take it to use in another exchange rather than because it is the exact object they need now.

There is no need to turn this into a single ladder from barter to shells to coins. Different communities and periods need their own evidence. We tested matching wants and read one documented example. Those are useful clues, not the whole history of money.