int x1 = 175;
int y1 = 175;

void setup(){
  size(400, 400); // size of the window
  background(0, 0, 0); //background color
  frameRate(30);
}

void draw() {
    //background(0, 0, 0); // comment this out for snake
    fill(0, 255, 0);
    rect(x1, y1, 10, 10);
}

void keyPressed(){
  if (keyCode == UP) {
  y1= y1-10;
  }
  if (keyCode == DOWN) {
  y1= y1+10;
  }
  if (keyCode == RIGHT) {
  x1= x1+10;
  }
  if (keyCode == LEFT) {
  x1= x1-10;
  }
}