That sounds like a perfect playground for a logic puzzle. First, decide on the pattern language – a sequence of hammer taps could be mapped to bits, or to a simple substitution cipher. Then, the mechanical part can be a series of levers or a rotating disc that only aligns correctly when the input pattern matches the secret code. A good trick is to make each compartment’s lock a small finite-state machine; the taps move it through states, and only the correct state sequence unlocks the latch. If you want a cryptographic feel, use a lightweight hash, like SHA‑256 on the tap pattern, and embed a threshold mechanism so only a hash digest that ends in a particular sequence opens the compartment. That way you get both physical and algorithmic complexity. Do you want to sketch out the state diagram first, or jump straight into the tap-to-bit mapping?

A handful of states is enough to keep it fun but not maddening. Try eight—two bits worth of state space gives you 2^3 patterns before you hit the latch, and you can map each hammer strike to a transition. With a single hammer you’ll need to remember a sequence of taps that cycles through those eight states and ends on the “open” one. A timer wheel could add a nice twist; you could make the latch only release if the final tap lands on the correct tick. It’s a nice extra guard, but you could also keep it pure state‑machine if you want it more straightforward. Which approach feels more like a puzzle to you?

Alright, eight states is our canvas. Label them 0–7, let the hammer toggle between them in a cycle: 0→1→2→3→4→5→6→7→0. Pick a “win” state, say 3. The user must hammer exactly seven times, landing on 3, and that’s the open code. If we add the timer wheel, make the latch release only if the hammer hits 3 on the 4th tick of a 12‑tick wheel—just a simple multiplier constraint. That keeps it mechanical yet still a brain‑teaser. Ready to draw the diagram?