Modify a text file: $/fastball.pde

$/fastball.pde

//// Billiard table, with moving balls.
//// 7327b:  Demonstrate simple classes, constructors.
////    Swap velocities, when balls hit.
String title=  "Demonstrate simple classes, constructors.";
String author="Prof.BAM:7327b";

float left=50, top=50, right=550, bottom=350, bump=25;
float xspeed=3,yspeed=3,fast=1;    // Velocity (pixels per frame); speedup
int score=0;

//// Instantiate the balls and pockets.
Ball red, yellow, blue;

void setup() {
  //// Setup:  600x400 (for 300x500 table).
  size(600,400);
  ////  Initialize the 3 balls.
  red=       new Ball();
  red.c=     color(255,0,0);
  yellow=    new Ball();
  yellow.c=  color(255,255,0);
  blue=      new Ball();
  blue.c=    color(0,0,200);
  reset();
}
void reset() {
  //// Randomize the ball positions.
  red.x=    left+random(200);   red.y=     top+50;
  yellow.x= left+random(200);   yellow.y=  top+100;
  blue.x=   left+random(200);   blue.y=    top+150;
  fast=1;
}

void draw() {
  //// Table, with billiard balls.
  drawTable();
  moveBalls();
  drawBalls();
}
void  drawBalls() {
  //// Draw each ball.
  red.show();
  yellow.show();
  blue.show();
}

void  drawTable() {
  //// Draw 500x300 green light-table, with thick brown border, on tan backgroud.
  background( 250,200,50 );    // Orange floor.
  text( title, 25, 20);
  text( author, width-100, height-10 );
  //  
  fill( 255,0,0);
  text( "SCORE:  "+score, 400, 10 );
  fill( 0,0,200);
  text( "Press 'R' key to restart (randomly), 'Q' to quit.", 25, height-25);
  float f=  int(fast*100) / 100.0;
  fill(127);
  text( "    fast="+ f +"   +/- for faster/slower.", 25, height-12);
  //// Table:
  fill( 100,200,100 );          // Light-green table.
  stroke( 100,50,50 );          // Brown (wood) rail.
  strokeWeight(25);
  rectMode(CORNERS);
  rect(left,top, right,bottom);        // Table (with rail);
  rectMode(CORNER);
  strokeWeight(1);
}

void  moveBalls() {
  //// Move each ball, based on its velocity (dx,dy),
  //// and detect hits.
  red.move();
  yellow.move();
  blue.move();
  //// Check for collisions.
  check( red, yellow );
  check( red, blue );
  check( yellow, blue );
}

void check( Ball p, Ball q) {
  //// Check for collisions; reverse both if hit.
  if (dist( p.x,p.y, q.x,q.y) < 20) {
    score += 10;
    /*  (Swap code like this will NOT work.)
      p.dx=  -p.dx;
      p.dy=  -p.dy;
      q.dx=  -q.dx;
      q.dy=  -q.dy;
    */
    // Swap velocities.
    float tmp;
    tmp = p.dx;
    p.dx=  q.dx;
    q.dx=  tmp;
    tmp = q.dx;
    q.dx=  p.dx;
    p.dx=  tmp;
    //// Eliminate "ringing" (by moving both in new direction.
    p.x += 2*p.dx;    p.y +=  2*p.dy;
    q.x += 2*q.dx;    q.y +=  2*q.dy;
    //// Also flash ball colors, and show text above.
    background(0);
    p.show();
    q.show();
    fill(255);
    text( "H I T !", p.x, p.y-20 );
  }
}
////// EVENTS //////
void keyPressed() {
  //// "R" restarts game.
  if (key=='R') { reset(); }
  //// "Q" quits game.
  if (key=='Q') { exit();  }
  //// "+/-" speeds-up/slows-down.
  if (key=='+') { fast *= 1.1; }
  if (key=='-') { fast *= 0.9; }
}

/////////////////  CLASSES:
class Ball {
  //// Billiard ball.
  color c;
  float x=0,y=0;    // Position of this ball.
  float dx=xspeed,dy=yspeed;  // Velocity (pixels per frame).
  float diam=20;    // Diameter is 20.

//// CONSTRUCTORS ////

//// METHODS  ////
  void move() {
    //// Move ball by (dx,dy)
    x=  x + dx*fast;
    y=  y + dy*fast;
    // Bounce off walls.
    if (x < left+bump)   { dx=  -dx;   x=left+2*bump; }
    if (x > right-bump)  { dx=  -dx;   x=right-2*bump; }
    if (y < top+bump)    { dy=  -dy;   y=top+2*bump; }
    if (y > bottom-bump) { dy=  -dy;   y=bottom-2*bump; }
  }
  void show() {
    //// Draw at (x,y)
    fill(c);
    ellipseMode(CENTER);
    ellipse(x,y, diam,diam);
  }
}