void setup() {
  size(100, 100);
  stroke(255);
}

void draw() {
  background(0);
  fill(80);
  noStroke();
  // Angles for sin() and cos() start a 3 o'clock,
  // subtract HALF_PI to make them start at the top
  ellipse(50, 50, 80, 80);
  float s = map(second(), 0, 60, 0, TWO_PI) - HALF_PI;
  float m = map(minute(), 0, 60, 0, TWO_PI) - HALF_PI;
  float h = map(hour() % 12, 0, 12, 0, TWO_PI) - HALF_PI;
  stroke(255);
  line(50, 50, cos(s) * 38 + 50, sin(s) * 38 + 50);
  line(50, 50, cos(m) * 30 + 50, sin(m) * 30 + 50);
  line(50, 50, cos(h) * 25 + 50, sin(h) * 25 + 50);
}