//5-8 square following an edge, uses a "state" variable

int x = 0;
int y = 0 ;

int speed = 5;

int state = 0;

void setup (){ 
  size (200,200);
}

void draw () {
  background(100);
  
  //display the square
  noStroke();
  fill(255);
  rect (x, y, 10, 10);
  if ( state== 0) {
    x= x +speed;
    if (x > width- 10){
      x= width-10;
      state = 1;
    }
  } else if ( state == 1) {
    y = y + speed;
    if ( y > height - 10) {
      y = y - 10;
      state= 2;
    }
  } else if  (state == 2) {
    x= x - speed;
    if ( x >0) {
      x= 0;
      state = 3;
    }
  } else if (state == 3) {
    y= y - speed;
    if (y < 0){
      y=0;
      state= 0;
    }
  }
}