Arduino Ball Draw

/*
* Arduino Ball
* ------------
*
* Draw balls randomly on the screen, size controlled by a device
* on a serial port. Press space bar to clear screen, or any
* other key to generate fixed-size random balls.
*
* Receives an ASCII number over the serial port,
* terminated with a carriage return (ascii 13) then newline (10).
*
* This matches what Arduino's "Serial.println(val)" function
* puts out.
*
* Created 25 October 2006
* copyleft 2006 Tod E. Kurt * http://todbot.com/
*/

import processing.serial.*;

// Change this to the portname your Arduino board
String portname = "/dev/tty.usbserial-A3000Xv0"; // or "COM5"

Serial port;
String buf="";
int cr = 13; // ASCII return == 13
int lf = 10; // ASCII linefeed == 10

void setup() {
size(300,300);
frameRate(10);
smooth();
background(40,40,40);
noStroke();
port = new Serial(this, portname, 9600);
}

void draw() {
}

void keyPressed() {
if(key == ' ') {
background(40,40,40); // erase screen
}
else {
int x = int(random(0,width));
int y = int(random(0,height));
drawball(x,y, 50);
}
}

// draw a ball
void drawball(int x, int y, int r) {
for( int i=0; i<100; i++ ) {
fill(255-i,i,240);
ellipse(x,y+i, r,r);
}
}

// called whenever serial data arrives
void serialEvent(Serial p) {
char c = port.readChar();
if( c == '!' ) {
// do something A
} else if( c == '@' ) {
// do something B
}
int x = int(random(0,width));
int y = int(random(0,height));
drawball(x,y, 50);
}