[Description]

- Geometric collision (in processing) triggers the DC motor as a haptic feedback.

 [Components]

- DC Motor X 1

- Resistor X 2

- Transistor X 1

[Arduino Code]

char val; // Data received from the serial port
int potPin = 0;   // select the input pin for the potentiometer
int motorPin = 9; // select the pin for the Motor
void setup() {
  pinMode(motorPin, OUTPUT); // Set pin as OUTPUT
  Serial.begin(9600);
}
void loop() {
  if (Serial.available()) { // If data is available to read,
    val = Serial.read(); // read it and store it in val
  }
  if (val == 'H') { // If H was received
    digitalWrite(motorPin, HIGH); // turn the LED on
    delay(1000);
  } else {
    digitalWrite(motorPin, LOW); // Otherwise turn it OFF
  }
  delay(100); // Wait 100 milliseconds for next reading 
}

[Processing Code]

import processing.serial.*;

Serial port; // Create object from Serial class

// Global variables for the ball
float ball_x;
float ball_y;
float ball_dir = 1;
float ball_size = 5;  // Radius
float dy = 0;  // Direction

// Global variables for the paddle
int paddle_width = 5;
int paddle_height = 20;

int dist_wall = 15;

void setup()
{
  size(200, 200);
  rectMode(CENTER_RADIUS);
  ellipseMode(CENTER_RADIUS);
  noStroke();
  smooth();
  ball_y = height/2;
  ball_x = 1;
  // Open the port that the board is connected to and use the same speed (9600 bps)
  port = new Serial(this, 9600);
}

void draw()
{
  background(51);
 
  ball_x += ball_dir * 1.0;
  ball_y += dy;
  if(ball_x > width+ball_size) {
    ball_x = -width/2 - ball_size;
    ball_y = random(0, height);
    dy = 0;
  }
 
  // Constrain paddle to screen
  float paddle_y = constrain(mouseY, paddle_height, height-paddle_height);

  // Test to see if the ball is touching the paddle
  float py = width-dist_wall-paddle_width-ball_size;
  if(ball_x == py
     && ball_y > paddle_y - paddle_height - ball_size
     && ball_y < paddle_y + paddle_height + ball_size) {
    ball_dir *= -1;
    if(mouseY != pmouseY) {
      dy = (mouseY-pmouseY)/2.0;
      if(dy >  5) { dy =  5; }
      if(dy < -5) { dy = -5; }
    }
  }
 
  // If ball hits paddle or back wall, reverse direction
  if(ball_x < ball_size && ball_dir == -1) {
    ball_dir *= -1;
    port.write('H');             
  }
 
  // If the ball is touching top or bottom edge, reverse direction
  if(ball_y > height-ball_size) {
    dy = dy * -1;
  }
  if(ball_y < ball_size) {
    dy = dy * -1;
  }

  // Draw ball
  fill(255);
  ellipse(ball_x, ball_y, ball_size, ball_size);
 
  // Draw the paddle
  fill(153);
  rect(width-dist_wall, paddle_y, paddle_width, paddle_height); 
}

 [Picture]

- More to come