/* 
 title: bouncing ball 
 description: ball deflects off sketch window edges 
 created: August 9, 2005 by: Ira Greenberg 
 modified: With 3 balls, and initial random ball
           placement, Sept. 13, 2006 by Fred Green
 */ 
 
// declare global variables 
int x1speed, y1speed; 
int x2speed, y2speed;
int x1pos, y1pos, x2pos, y2pos, wdth, ht; 
int x3speed, y3speed, x3pos, y3pos;
 
//initialize sketch 
void setup(){ 
  
  //set sketch window size and background color 
  size(500, 400); 
  background(0); 
   
  //ball speed 
  x1speed = 3; 
  y1speed = 4;
 
  //other ball speed
  x2speed = 5;
  y2speed = 6; 
  
  x3speed = 7;
  y3speed = 8;
   
  //ball size 
  wdth = 20; 
  ht = 20; 
   
  // turn off shape stroke rendering 
  noStroke(); 
  
 //initial ball placement 
  x1pos = (int)random(10, width-10); 
  y1pos = (int)random(10, height-10); 
  x2pos = (int)random(10, width-10);
  y2pos = (int)random(10, height-10);
  x3pos = (int)random(10, width-10);
  y3pos = (int)random(10, height-10);
  
 //set the animation loop speed 
  frameRate(30); 
} 
 
// begin animation loop 
void draw(){ 
 
  //update background 
  background(0); 
  
  //draw balls
  fill(200, 200, 0);
  ellipse(x1pos, y1pos, wdth, ht); 
  ellipse(x2pos, y2pos, wdth, ht);
  ellipse(x3pos, y3pos, wdth, ht);
 
  //upgrade position values 
  x1pos+=x1speed; 
  y1pos+=y1speed;  
  x2pos+=x2speed;
  y2pos+=y2speed;
  x3pos+=x3speed;
  y3pos+=y3speed;
 
  //Detect collisions with walls:
  detectCollisions();
    
}

void detectCollisions()
{
  if (x1pos>=width-wdth/2 || x1pos<=wdth/2){ 
    x1speed*=-1; 
  } 
  if (y1pos>=height-ht/2 || y1pos<=ht/2){ 
    y1speed*=-1; 
  } 
  if (x2pos>=width-wdth/2 || x2pos<=wdth/2){ 
    x2speed*=-1; 
  } 
  if (y2pos>=height-ht/2 || y2pos<=ht/2){ 
    y2speed*=-1; 
  } 
  if (x3pos>=width-wdth/2 || x3pos<=wdth/2){ 
    x3speed*=-1; 
  } 
  if (y3pos>=height-ht/2 || y3pos<=ht/2){ 
    y3speed*=-1; 
  } 
}