linedraw.java

void setup() {
  size(480, 270);
  background(255);
}

void draw() {
  //change the stroke weight to have a thicker line
  strokeWeight(25);
  
  //use the random function to get a random color for the stroke
  stroke(random(0,255),random(0,255),random(0,255));
  
  //draw a line from previous mouse location to current mouse location
  line(pmouseX, pmouseY, mouseX, mouseY);
}

void mousePressed() {
  //reset the background when the mouse is pressed
  background(255);
}

void keyPressed() {
  //reset the background when certain keys are pressed
  if (key == 'a') {
    background(0);
  }
  else if (key == 's') {
    background(255,0,0);
  }
  else if (key == 'd') {
    background(0,255,0);
  }
  else if (key == 'f') {
    background(0,0,255);
  }
  else if (key == 'r') {
    background(random(0,255),random(0,255),random(0,255));
  }
}