Balls trying to bounce

int numCircles = 20;

float[] circleX = new float [numCircles];

float[] circleY = new float [numCircles];

float[] velocity = new float [numCircles];

​

int dia = 50;

float gravity = 0.2;

​

void setup () {

  size (500, 500);

  smooth();

  noStroke();

  background(255);

​

  for (int i=0; i<numCircles; i++) {

    circleX[i]=random(width);

    circleY[i]=random(height);

    velocity[i]=random(1, 5);

  }

}

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void draw () {

  background (255);

  fill (50);

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  circle();

}  

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void circle() {

​

  for (int i=0; i<numCircles; i++) {

    ellipse (circleX[i], circleY[i], dia, dia);

    circleY[i] += velocity[i];

    velocity[i] += gravity;

​

    if (circleY[i]> height-dia||circleY[i]<dia) {

      circleY[i]= height-dia;

      velocity[i] = velocity[i] * -0.75;

    }

  }

​

  for (int i=0; i<numCircles; i++) {

    for (int j=0; j<i+1; j++) {

      if (dist(circleX[i], circleY[i], circleX[i], circleY[i]) < dia) {

        velocity[i] *= -1;

      }

    }

  }

}

​

​

​