Build a low-level alert only after choosing a sensor suited to the tank and calibrating actual empty and full points.
Identify whether a breakout contains HMC5883L or the common QMC5883L alternative, then calibrate hard-iron and soft-iron distortion before computing heading.
Build a timed code-entry game with consistent indicators and non-blocking timing; it is a game rather than an access-control system.
Decode the actual button codes of an IR remote and toggle four current-limited LEDs while handling repeat frames and debounce.