// FreezeDemo D. Parson 3/20/2018
// Find "isFrozen" below to see how to freeze & unfreeze the display for debugging.
boolean isFrozen = false ;  // keyPressed() 'f' toggles for debugging
// Example 9-9: An array of Car objects

// An array of 100 Car objects!
Car[] cars = new Car[180]; 

void setup() {
  size(480, 360);
  // Initialize each Car using a for loop.
  for (int i = 0; i < cars.length; i ++ ) { 
    cars[i] = new Car(color(i*2), 0, i*2, i/20.0);
  }
}

void draw() {
  if (isFrozen) {
    return ;
  }
  background(255);
  // Run each Car using a for loop.  
  for (int i = 0; i < cars.length; i++) { 
    cars[i].move();
    cars[i].display();
  }
}

void keyPressed() {
  if (key == 'f') {
    isFrozen = ! isFrozen ; // toggle isFrozen from true to false, or false to true
  }
}

// The Car class does not change whether one car, 
// 100 cars or 1,000 cars!
class Car { 
  color c;
  float xpos;
  float ypos;
  float xspeed;

  Car(color c_, float xpos_, float ypos_, float xspeed_) {
    c = c_;
    xpos = xpos_;
    ypos = ypos_;
    xspeed = xspeed_;
  }

  void display() {
    rectMode(CENTER);
    stroke(0);
    fill(c);
    rect(xpos,ypos,20,10);
  }

  void move() {
    xpos = xpos + xspeed;
    if (xpos > width) {
      xpos = 0;
    }
  }
}