Alex's spot sketch, modified as we did in class.

alex-spot-sketch.pde

// Alex's spot sketch.
// It could use more comments.
// Steve Lambert 2015-11-02 

Spot[] spots; // Declare array

float gravity = 0.005;

float r;
float g;
float b;
float a;

void setup() {
  //size(1000, 400, P2D);
  fullScreen(P2D);
  int numSpots = 100; // Number of objects
  //int dia = width/numSpots; // Calculate diameter
  //int dia = round(random(1,10));
  int dia = 1;
  spots = new Spot[numSpots]; // Create array
  for (int i = 0; i < spots.length; i++) {
    float x = map(i,0,spots.length,0,width); // this places the dots across the top at the beginning
    float rate = random(0.1, 2.0);
    
    // Create each object:
    spots[i] = new Spot(x, 10, i, rate);
  }
  noStroke();
 
}
void draw() {
 // random colors
  r = random(255);
  g = random(255);
  b = random(255);
  a = random(255);
  
  fill(0);
  rect(0, 0, width, height);
  fill(r,g,b,a);
  for (int i=0; i < spots.length; i++) {
    spots[i].move(); // Move each object
    spots[i].display(); // Display each object
    spots[i].gravity(); // Gravity
     }
     
  }

class Spot {
  float x, y;         // X-coordinate, y-coordinate
  float diameter;     // Diameter of the circle
  float speed;        // Distance moved each frame
  int direction = 1;  // Direction of motion (1 is down, -1 is up)
  
  // Constructor
  Spot(float xpos, float ypos, float dia, float sp) {
    x = xpos;
    y = ypos;
    diameter = dia;
    speed = sp;
  }
    
  void move() {
    y += (speed * direction); 
    if ((y > (height - diameter/2)) || (y < diameter/2)) { 
      direction *= -1; 
    } 
  }
  
  void display() {
    ellipse(x, y, diameter, diameter);
  }
  
  void gravity() {
    speed = speed + gravity;
  }
  
  
}