(9) Breakout game in processing

To make a "complete" game, probably with bugs and quirks, we just need to put together the paddle, moving ball, and the disappearing blocks. Well, and add some final touched such as introducing a level (ball speeds up for each level) and to add detection if the ball hit the sides of the blocks for just bouncing in the horizontal direction. Adding it together and adding those touches produces this code:

// We will have 20 blocks. blocks[i]==1 means it still exists
int[] blocks = new int[20];
// Variables to keep track of position and speed of ball
int x = 250 + int(random(-80,80));
int y = 350;
int x_speed = 3;
int y_speed = -3;
// Variables to keep track of paddle
int x_paddle = 250, y_paddle = 370;
int paddle_width_half = 40;
// keep score 
int score = 0;
int level = 1;
int wait = 0;

// Run once at start
void setup() {
  int i;
  // 500 pixels wide, 400 pixel height
  // This call will set system variables (width, height)
  size(500, 400);
  rectMode(CENTER);
  // All blocks exist
  for (i=0; i<20; i++) {
    blocks[i] = 1;
  }
}

// Called every re-draw, defaul 30 times per second
void draw() {
  int i, x_tmp, y_tmp;
  int blocks_gone;

  // Update ball position by adding speed
  x = x + x_speed;
  y = y + y_speed;
  if (x>width || x<0)  
    x_speed = -x_speed;
  if (y<0)
    y_speed = -y_speed;

  // Check if keys are pressed
  if (keyPressed) {
    if (keyCode == RIGHT || key == 'd') {
      // Move paddle right
      x_paddle = x_paddle + 8;
    } else if (keyCode == LEFT || key == 'a') {
      // Move paddle left
      x_paddle = x_paddle - 8;
    } else if (key == ' ') {
      // Restart
      x = 250 + int(random(-80,80));
      y = 350;
      x_speed = 3;
      y_speed = -3;
      x_paddle = 250;
      score = 0;
      level = 1;
      // All blocks exist
      for (i=0; i<20; i++) {
        blocks[i] = 1;
      }
    }
  }

  // Check if ball collides with paddle
  if ((x_paddle-paddle_width_half)<x && (x_paddle+paddle_width_half)>x && 
    (y_paddle-10)<y && (y_paddle)>y) {
    // ball is hitting paddle rectangle, reverse y_speed
    y_speed = -y_speed;
    score = score + 1;
  }

  // Clear screen to black
  background(0);
  // Set fill color to white
  fill(255);
  // Display score
  textSize(16);
  textAlign(RIGHT);
  text("Score", 80, 390);
  textAlign(LEFT);
  text(score, 90, 390);
  // Display level
  textAlign(RIGHT);
  text("Level", 450, 390);
  textAlign(LEFT);
  text(level, 460, 390);

  // Draw a circle at position x,y, 10 pixels large
  ellipse(x, y, 10, 10);
  // draw paddle
  rect(x_paddle, y_paddle, paddle_width_half*2+1, 11);
  if (y>height) {
    textSize(40);
    textAlign(CENTER);
    text("Game over", 250, 250);
  }

  blocks_gone = 1;
  // Loop through all the potential blocks
  for (i=0; i<20; i++) {
    // Calculate the x,y position of upper right corner
    x_tmp = i%5*100+10; // %5 is modulus - will result 0-4 always 
    y_tmp = 40*(i/5)+10; 
    // Check if we we have a block (blocks[x] is 1)
    if (blocks[i]==1) { 
      // Draw the block
      rect(x_tmp+40, y_tmp+10, 80, 20);
      // Since we drew a block, all are not gone
      blocks_gone = 0;
    }
    // Check if ball is over the block, if so, remove it (blocks[i]=0) 
    // first check bounce on top/bottom
    if (x>(x_tmp+4) && x<(x_tmp+76) &&
      y>y_tmp && y<(y_tmp+20) && blocks[i]==1) { 
      blocks[i]=0;
      y_speed = -y_speed;
      score = score + 5;
    }
    // first check bounce on sides
    if (((x>(x_tmp-5) && x<x_tmp) || (x>(x_tmp+80) && x<(x_tmp+85))) &&
      y>y_tmp && y<(y_tmp+20) && blocks[i]==1) { 
      blocks[i]=0;
      x_speed = -x_speed;
      score = score + 5;
    }
    // first check bounce on sides
    if (((x>(x_tmp-1) && x<(x_tmp+5)) || (x>(x_tmp+75) && x<(x_tmp+81))) &&
      y>y_tmp && y<(y_tmp+20) && blocks[i]==1) { 
      blocks[i]=0;
      x_speed = -x_speed;
      y_speed = -y_speed;
      score = score + 5;
    }
  }
  if (blocks_gone==1 && wait<200) {
    textSize(40);
    textAlign(CENTER);
    text("Level cleared...", 250, 210);
    text("Preparing next level", 250, 290);
    x = 250;
    y = 350;
    x_speed = 0;
    y_speed = 0;
    wait++;
    if (wait==200) {
      wait = 0;
      x = 250 + int(random(-80,80));;
      y = 350;
      x_speed = 3+level;
      y_speed = -3-level;
      x_paddle = 250;
      level++;
      // All blocks exist
      for (i=0; i<20; i++) {
        blocks[i] = 1;
      }
    }
  }

}

And this gameplay: