Snack machines

The ladder

1. Ages 3–5
   • One Coin, One SnackFind the snack by row and place, then payOpen →
2. Ages 6–8
   • Press the CodeRead a snack code as row and columnOpen →
   • Exact Change OnlyBuild eighty-five cents from coins three waysOpen →
3. Ages 9–14
   • The Machine’s MemoryRead a machine's money states and fix the dead endsOpen →
   • Fewest CoinsMake change with fewest coins and find where greedy failsOpen →
   • Fill the SlotWork out how long a full slot lastsOpen →
4. Ages 15–18
   • What a Sale LeavesTake costs off a sale and compare markup with marginOpen →
   • Stock the SlotChoose a stock level that balances misses and wasteOpen →
   • The Vending AutomatonWrite a coin machine as states and test itOpen →

Two rules every rung keeps

The Fade Rule. Every game ends on a plain screen: the same numbers with the snack machines words gone, so the maths leaves with you.

The Own-Lane Rule. Your numbers are compared only with your own past, never with anyone else's, and they stay on this device.

Problems built on something you love help most when the context carries the maths, not when it decorates it. These ladders are a design, not a promise.

Ask a grown-up tonight: “What do you think the machine has to remember to give the right change?”