Follow1

/**
 * Follow 1
 * based on code from Keith Peters.
 *
 * A line segment is pushed and pulled by the cursor.
 */

float x = 100;
float y = 100;
float angle1 = 0.0;
float segLength = 50;

void segment(float x, float y, float a);

void setup() {
  size(640, 360);
  strokeWeight(20.0);
  stroke(255, 100);
}

void draw() {
  background(0);

  float dx = mouseX - x;
  float dy = mouseY - y;
  angle1 = atan2(dy, dx);

  x = mouseX - (cos(angle1) * segLength);
  y = mouseY - (sin(angle1) * segLength);

  segment(x, y, angle1);

  ellipse(x, y, 20, 20);
}

void segment(float x, float y, float a) {
  pushMatrix();
  translate(x, y);
  rotate(a);
  line(0, 0, segLength, 0);
  popMatrix();
}