void setup() {
  size(600, 800);
  background(0); 
  stroke(300);
  strokeWeight(1);
}

void draw() {
  if(mousePressed){
    mirrorDraw();
  }
}

void keyPressed() {
  if (key == '1') {
    strokeWeight(1);
  } else if (key == '2') {
    strokeWeight(6);
  } else if (key == '3') {
    strokeWeight(12);
  } else if (key == 'w') {
    stroke(300);
  } else if (key == 'b') {
    stroke(0);
  } else if (key == 's'){
   saveImage(); 
  } 
}

void saveImage() {
  save("output.jpg");
}

void mirrorDraw() {
  line(pmouseX, pmouseY, mouseX, mouseY);
  line(width-pmouseX, pmouseY, width-mouseX, mouseY);
  line(pmouseX, height-pmouseY, mouseX, height-mouseY);
  line(width-pmouseX, height-pmouseY, width-mouseX, height-mouseY);
}