Build your own Cold War-era countdown timer prop with John Park’s Mystery Box: Crypto Countdown Case learning guide. This mystery box is a Soviet themed launch-code box complete with missile switch covered toggles, a Feather microcontroller with red 14-segment display, and stress-inducing piezo buzzer. Use it for an escape room, prop, or wedding proposal. Your players, or potential spouse-to-be, will need to enter the correct five-switch sequence to defuse the device before all is lost. (Note: this project is a harmless prop, not an actual bomb.) Customize it with your own secret message.