Cat laser toy on an Arduino Uno

// Cat laser toy: a KY-008 laser on a pan and tilt pair of servos.
//
//   pin 7    the laser's S (the laser runs from the pin itself)
//   pin 9    the pan servo's signal
//   pin 10   the tilt servo's signal
//   pin 2    the button, to GND (INPUT_PULLUP: pressed reads LOW)
//   rails    5 V and ground for the servos and the laser
//
// A round is a minute of the dot wandering around the floor: pick a spot,
// glide to it a degree at a time, pause, pick another. Then the laser goes
// off and the servos rest until the button asks for another round.
//
// The tilt never goes above 60 degrees from straight down, so the dot stays
// on the floor and out of anyone's eyes.

#include <Servo.h>

const int LASER = 7;
const int PAN = 9;
const int TILT = 10;
const int BUTTON = 2;

const unsigned long ROUND_MS = 60000;
const int PAN_MIN = 30, PAN_MAX = 150;
const int TILT_MIN = 100, TILT_MAX = 160;

Servo pan;
Servo tilt;
int panAt = 90;
int tiltAt = 130;
int rounds = 0;

void glideTo(int panTo, int tiltTo) {
  while (panAt != panTo || tiltAt != tiltTo) {
    if (panAt < panTo) panAt++;
    if (panAt > panTo) panAt--;
    if (tiltAt < tiltTo) tiltAt++;
    if (tiltAt > tiltTo) tiltAt--;
    pan.write(panAt);
    tilt.write(tiltAt);
    delay(15);
  }
}

void play() {
  rounds++;
  Serial.print("round ");
  Serial.print(rounds);
  Serial.println(": laser on");
  digitalWrite(LASER, HIGH);
  unsigned long start = millis();
  while (millis() - start < ROUND_MS) {
    int p = random(PAN_MIN, PAN_MAX + 1);
    int t = random(TILT_MIN, TILT_MAX + 1);
    Serial.print("dot to ");
    Serial.print(p);
    Serial.print(", ");
    Serial.println(t);
    glideTo(p, t);
    delay(random(200, 900));
  }
  digitalWrite(LASER, LOW);
  glideTo(90, 130);
  Serial.println("resting: press the button to play again");
}

void setup() {
  Serial.begin(115200);
  Serial.println("Mokxi Arduino Uno: cat laser toy");
  pinMode(LASER, OUTPUT);
  pinMode(BUTTON, INPUT_PULLUP);
  pan.attach(PAN);
  tilt.attach(TILT);
  pan.write(panAt);
  tilt.write(tiltAt);
  randomSeed(analogRead(A0));
  play();
}

void loop() {
  if (digitalRead(BUTTON) == LOW) play();
  delay(20);
}