I'm not sure how to write my code so that when i'm moving to the right and i press 'a' to go to the left, i don't crash into myself. Thanks.

int x=50;
int y=200;
int direction = RIGHT;
void setup()
{
size(400,400);
  background(0);
  noFill();
  stroke(0,150,150);
  rect(20,20,360,360);
}

void draw()
{
    human();
}

void human()
{
  stroke(255,255,255);
  if(get(x,y) != color(0,0,0))
  {
    fill(255,0,0);
    ellipse(150,150,200,200);
    stroke(0,255,0);
  }
  else
  {
    point(x,y);
    if(direction == RIGHT)
    {
      x++;
    }
    else if(direction == LEFT)
    {
      x--;
    }

    else if(direction == UP)
    {
      y--;
    }

    else if( direction == DOWN)
    {
      y++;
    }
  }
}

void keyPressed()
{
  if (key == 'a')
  {
    direction= LEFT;
  }
  if (key == 'd')
  {
    direction= RIGHT;
  }
  if (key == 'w')
  {
    direction= UP;
  }
  if (key == 's')
  {
    direction= DOWN;
  }
}