// this is very simple line drawing , i tried other ways to do the drawing but keep
// failing at it. So i just kept this very simple and basic.
 
void setup() {
  size(400, 400); // size of composition    
  background(0); //the back ground color , 0 is black up to 255 is white, in this case
  // we kept it back.
}

void draw() {
  stroke(255);
  if(mousePressed) { // this is the mousepressed, controls that lets the computer know that mouse button is active.
    line(mouseX, mouseY, pmouseX, pmouseY); 
  }
}