/* built with Studio Sketchpad: 
 *   https://sketchpad.cc
 * 
 * observe the evolution of this sketch: 
 *   https://friendscentral.sketchpad.cc/sp/pad/view/ro.9s-xPPzhhEH/rev.111
 * 
 * authors: 
 *   Colin Angevine

 * license (unless otherwise specified): 
 *   creative commons attribution-share alike 3.0 license.
 *   https://creativecommons.org/licenses/by-sa/3.0/ 
 */ 



Projectile x;

void setup() {
  size(500, 500);
  x = new Projectile();
}
void draw() {
  background(255);
  x.update();
  PVector gravity = new PVector(0, 0.5 * x.mass);
  x.applyForce(gravity);
  x.display();
}
void mouseClicked() {
  x.launch();
}

class Projectile {
  PVector location;
  PVector velocity;
  PVector acceleration;
  float mass;
  
  Projectile() {
    mass = random(1, 4);
    location = new PVector(50, 50);
    velocity = new PVector(0, 0);
    acceleration = new PVector(0, 0);
  }
  
  void launch() {
    location = new PVector(0, 400);
    velocity = new PVector(random(7, 10), random(-7, -15));
  }
  
  void applyForce(PVector force) {
    PVector f = PVector.div(force, mass);
    acceleration.add(f);
  }
  
  PVector calculateFriction() {
    float c = 0.01;
    PVector friction = velocity.get();
    friction.mult(-1);
    friction.normalize();
    friction.mult(c);
    return friction;
  }
  
  void update() {
    velocity.add(acceleration);
    location.add(velocity);
    acceleration.mult(0);
    
    if (location.x < 0) {
      location.x = 0;
      velocity.x = velocity.x * -.9;
      PVector friction = calculateFriction();
      applyForce(friction);
    }
    if (location.x > width) {
      location.x = width;
      velocity.x = velocity.x * -.9;
      PVector friction = calculateFriction();
      applyForce(friction);
    }
    if (location.y > height) {
      location.y = height;
      velocity.y = velocity.y * -.9;
      PVector friction = calculateFriction();
      applyForce(friction);
    }
  }

  void display() {
    stroke(0);
    fill(175);
    rect(location.x, location.y, mass * 15, mass * 15);
  }
}