Inputs: buttons and sensors — the board starts to feel

Until now the board only "spoke" — now it "listens". Button: pinMode(2, INPUT_PULLUP) — built-in resistor, fewer wires; pressed = LOW. Sensors: photoresistor (light), DHT11/DHT22 (temperature+humidity, ~€3), HC-SR04 (ultrasonic distance), PIR (motion), DS18B20 (precise temperature). Analog sensors → analogRead gives 0–1023. The logic never changes: read sensor → decide (if) → switch something.

• ●INPUT_PULLUP — button with no external resistor
• ●A sensor starter kit (Elegoo/Freenove) ~€30–50 — enough for 20 projects
• ●The DHT11 is slow (1 reading/s) — don’t poll it more often