Build a cardboard arcade, with AI as your engineering assistant

A huge box turns up in the hallway, and normally it ends in the recycling. Before it gets flattened, there is a better idea: turn it into a fairground machine. A cardboard arcade needs scissors, glue, a few rubber bands and a lot of enthusiasm, and once it works, the whole family queues up in front of it.

What matters is who is in charge. The child is the engineer and the AI is the adviser, so nobody asks it for a finished plan: they ask it for questions. From seven it works with an adult on hand for the tricky cuts, and from nine or ten the child runs it almost alone. Whatever comes out of their own hands, wonky or not, they will defend for months.

Three machines to start with

• The marble run: kitchen roll tubes glued inside the box standing upright, a tray at the bottom, and holes worth different numbers of points.
• The claw machine: a string hanging through a hole in the lid, with a paper clip bent into a hook, and small prizes on the floor of the box. The cardboard version is hand operated and still hard enough.
• Pinball with rubber bands: box laid flat, two levers cut from stiff card, rubber bands stretched between drawing pins, and glued obstacles that score points.
• And the easiest of the lot: a box with three different sized holes for throwing a paper ball, which usually wins the party.

The prompt the child types

I want to build an arcade machine out of cardboard. I have [WHICH BOXES AND WHAT SIZE] and also [MATERIALS: rubber bands, string, tubes, drawing pins]. I am [AGE] years old. I want to build [WHICH MACHINE]. Do not give me a finished plan: ask me five questions first about my box and my idea, one at a time, so that I decide the design. Then give me the steps in short sentences, saying what gets cut and what gets glued, with no craft knife and no hot glue gun unless an adult is there. Also tell me the two things that usually go wrong with this kind of machine.

Once the machine works, the best part begins, and it is not the building but the inventing of the game: how many points each hole is worth, how many goes per coin, what you win. The prizes get made too: paper vouchers, a drawing to order, picking Friday's film. That is the moment the arcade stops being a craft project and becomes something the family uses for a whole Saturday.

My cardboard machine works. You play it like this: [HOW YOU PLAY]. Help me invent the game around it: suggest three names for my arcade, write three short rules a five year old can follow, a simple points system, and a list of five prizes that cost no money. Also write the opening poster, in big letters and under thirty words, so I can copy it by hand onto a piece of card.