int numVehicles = 5;   // how many vehicles we will have
Vehicle [] v = new Vehicle[numVehicles];

void setup() {

  size( 400,400 ); // sets the size of the environment
  frameRate(10);   // sets the number of draw loops per second 
  noStroke();      // sets the stroke on ellipses to none
  
  // this type of loop lets us perform some action to each vehicle
  for( int i = 0; i<numVehicles; i++ ) {
    v[i] = new Vehicle( random(0,400), random(0,400) );
  }

}

void draw() {
  for( int i = 0; i<numVehicles; i++ ) {
    v[i].drawMyself();
    v[i].updatePosition();
  } 
}








class Vehicle {
 
  // every vehicle will have these things:
  float xPos;
  float yPos;
  float speed;
  float direction;
  int myColor;
  
  Vehicle( float x, float y ) {
    xPos = x;
    yPos = y;  
    speed = 2;
    direction = random(0,360);    // the direction and 
    myColor = (int)random(0,255); // the color of every new 
                                  // vehicle will be random
  }
  
  void drawMyself() {
   fill( myColor );
   ellipse( xPos, yPos, 5, 5 ); 
  }
  
  void updatePosition() {
   xPos = xPos + speed * cos( radians(direction) );
   if( xPos > 400 || xPos < 0 ) {
     direction += 90;     
   } 
   yPos = yPos - speed * sin( radians(direction) );
   if( yPos > 400 || yPos < 0 ) {
     direction += 90;
   }
  }
 
}