# P4P2010-05-27

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Programming for Poets, class 5/27

We went through varibles and functions again, and introduced conditionals ("if") statements. We updated our pongball program to bounce!

```int ballx = 0; // start at left
int bally = 200; // and halfway down
int pballx = 0;
int pbally = 200;
int speed = 5; // the ball moves this number of pixels between frames

void setup() {
// size of our drawing window
size(400, 400);
// set the background color to gray
background(128);
}

void draw() {

// draw over the previous ball location
stroke(128); // gray
fill(128);
drawball(pballx,pbally);

// update the ball location
ballx = ballx + deltax;
bally = bally + deltay;

// check that ball is on the screen
if(ballx>400)
{
println("right bounce x");
deltax = -speed; // move left

}

if(bally>400)
{
println("bottom bounce y");
deltay = -speed; // now move up
}

if(ballx<1)
{
println("left bounce x");
deltax = speed; // now move right

}

if(bally<1)
{
println("top bounce y");
deltay = speed;
}

// now draw ball in new location
stroke(255);
fill(255); //white
drawball(ballx,bally);

// save the new location for next time
pballx = ballx;
pbally = bally;

}

// draw a paddle-shaped box at the given coordinates
void drawbox(int x, int y) {
rect(30,y,10,40);
}

// draw a ball at the given coordinates
void drawball(int foo, int bar) {
ellipse(foo,bar,10,10);
}

int myadd(int A, int B) {
return (A+B);
}
```