void setup()
{
  z = 0;
  size(900, 900);
  m = 0;
  P=loadFont("AngsanaUPC-30.vlw");
  textFont(P);
  startingTime = millis();
  xspeed = 5;

}

void draw()
{
 background(0);
  fill(255);
int seconds = (millis() - startingTime) / 1000;
   int minutes = seconds / 60;
   text((minutes) + ":" + (seconds),50,50);
  
 for (int i = 0; i < Snowflake.size(); i++)
  {
    if(Snowflake.get(i).getY() > height+ 100)
    {
        Snowflake.remove(i);
    }
    else
       Snowflake.get(i).display();
  }
if(z<10000000)
{
Snowflake.add(new Snowflake(random(0,900),0));
z++;
frameRate(25);
}

  fill(255,0,0);
  rect(mouseX, 850,20,20);
  fill(255,0,0);
  rect(460,450,35,35);

}
void time() {
  background(170);
  fill(255);

i want to make a bullet hit 1 of the pictures in the arraylist and if the bullet hits it, it disappears 

i have pictures on my arraylist and i want it to move side to side and if it hits the side of the screen it bounce back.

when x coordinate +/- with mouse, and change back to original picture when it stops?

..changing pictures when keypressed right or left and goes bk to normal when its not?

im trying to make something like a brick breaker but im stuck on trying to make the ball bounce off on all 4 sides of the paddle