codingMath05a

float angle;
float arrowX, arrowY, dx, dy;

PShape arrow;

void setup() {
  size(400, 400, P2D);

  arrowX = width / 2;
  arrowY = height / 2;

  angle = 0;

  arrow = createShape();

  arrow.beginShape();
  arrow.fill(0);
  arrow.noStroke();
  arrow.vertex(1,0);
  arrow.vertex(0,1);
  arrow.vertex(3,0);
  arrow.vertex(0,-1);
  arrow.endShape(CLOSE);
}

void draw() {
  background(255); // clear canvas

  dx = mouseX - arrowX;
  dy = mouseY - arrowY;

  angle = atan2(dy, dx);

  println(mouseX, mouseY, dx, dy, angle);

  translate(arrowX, arrowY);
  rotate(angle);

  shape(arrow, 0, 0, 20, 20);
}