KY switch modules on pins 2 to 6, on an Arduino Uno

// Five switch modules: a KY-031 knock module on pin 2, an SW-18010P spring
// switch on pin 3, a KY-017 mercury tilt module on 4, a KY-021 mini reed
// module on 5 and a KY-004 button module on 6.
//
//   KY-031 S -> pin 2   SW-18010P: pin 3 -> switch -> GND
//   KY-017 S -> pin 4   KY-021 S -> pin 5   KY-004 S -> pin 6
//   every + -> 5V   every - -> GND
//
// Each KY board has a 10k from + to S and its switch from S to -, so S is
// HIGH until the switch closes and pulls it LOW. The two springs touch their
// pins for a millisecond or two at a time, too quick to poll, so pins 2 and 3
// (the Uno's interrupt pins) catch them with attachInterrupt(). The bare
// spring switch has no resistor of its own: INPUT_PULLUP is it.
//
// Knock, tip the tilt module, drag the magnet and hold the button.

volatile bool knocked = false;
volatile bool shaken = false;

void knock() { knocked = true; }
void shake() { shaken = true; }

const int pins[] = {4, 5, 6};
const char *closed[] = {"tipped", "magnet", "pressed"};
const char *opened[] = {"upright", "no magnet", "released"};
int last[] = {-1, -1, -1};

void setup() {
  pinMode(2, INPUT);
  pinMode(3, INPUT_PULLUP);
  for (int i = 0; i < 3; i++) pinMode(pins[i], INPUT);
  attachInterrupt(digitalPinToInterrupt(2), knock, FALLING);
  attachInterrupt(digitalPinToInterrupt(3), shake, FALLING);
  Serial.begin(9600);
  Serial.println("Mokxi Uno: knock 2, spring 3, tilt 4, reed 5, button 6");
}

void loop() {
  if (knocked) {
    Serial.println("knock");
    delay(250);
    knocked = false;
  }
  if (shaken) {
    Serial.println("spring");
    delay(250);
    shaken = false;
  }
  for (int i = 0; i < 3; i++) {
    int now = digitalRead(pins[i]) == LOW ? 1 : 0;
    if (now != last[i]) {
      last[i] = now;
      Serial.println(now ? closed[i] : opened[i]);
    }
  }
  delay(10);
}