int armAngle = 0;
int angleChange = 5;
final int ANGLE_LIMIT = 135;

void setup()
{
  size(200, 200);
  smooth();
  frameRate(30);
}

void draw()
{
  background(255);
  pushMatrix();
  translate(mouseX,mouseY); // place robot so arms are always on screen
  drawRobot();
  armAngle += angleChange;
  
  // if the arm has moved past its limit,
  // reverse direction and set within limits.
  if (armAngle > ANGLE_LIMIT || armAngle < 0)
  {
    angleChange = -angleChange;
    armAngle += angleChange;
  }
  popMatrix();
}

void keyPressed() {
  save("robot.jpg");
}

void drawRobot()
{
  noStroke();
  fill(38, 38, 200);
  rect(20, 0, 38, 30); // head
  rect(14, 32, 50, 50); // body
  drawLeftArm();
  drawRightArm();
  rect(22, 84, 16, 50); // left leg
  rect(40, 84, 16, 50); // right leg
  
  fill(222, 222, 249);
  ellipse(30, 12, 12, 12); // left eye
  ellipse(47, 12, 12, 12);  // right eye
}

void drawLeftArm()
{
  pushMatrix();
  translate(12, 32);
  rotate(radians(armAngle));
  rect(-12, 0, 12, 37); // left arm
  popMatrix();
}

void drawRightArm()
{
  pushMatrix();
  translate(66, 32);
  rotate(radians(-armAngle));
  rect(0, 0, 12, 37); // right arm
  popMatrix();
}