float y1, y2;
float velocity1, velocity2;
float mass1 = 1.0;
float mass2 = 6.0;
float stiffness = 0.1;
float damping = 0.9;

void setup() {
  size(100, 100);
  noStroke();
}

void draw() {
  fill(0, 12);
  rect(0, 0, width, height);
  fill(255);
  float targetY = mouseY;
  float forceA = stiffness * (targetY - y1);
  float accelerationY1 = forceA / mass1;
  velocity1 = damping * (velocity1 + accelerationY1);
  y1 += velocity1;
  rect(10, y1, 40, 15);
  float forceB = stiffness * (targetY - y2);
  float accelerationY2 = forceB / mass2;
  velocity2 = damping * (velocity2 + accelerationY2);
  y2 += velocity2;
  rect(50, y2, 40, 15);
}