Keypad on d4–d7/d10–d12/a0 enters letter numbers, which are scrambled through Enigma rotor I wiring with a key set by the encoder (d2/d3, press a3) and a rotor position that the servo on d9 shows as a stepping turntable. The result appears on the TM1637 display (a1/a2), the buzzer on d13 clicks, and a breadboard acts as the 5V/GND power strip.