OPENGL Rotating rectangle

#include <GL/glut.h>
#include <cmath>

float angle = 0.0f;

void drawRectangle() {
  // Set the color of the rectangle
  glColor3f(1.0f, 0.0f, 0.0f);

  glPushMatrix();

  // Rotate y-axis
  glRotatef(angle, 0.0f, 1.0f, 0.0f);

  // Draw rectangle
  glBegin(GL_QUADS);
  glVertex2f(-0.5f, -0.5f);
  glVertex2f(0.5f, -0.5f);
  glVertex2f(0.5f, 0.5f);
  glVertex2f(-0.5f, 0.5f);
  glEnd();

  glPopMatrix();
}

void update(int value) {
  // Update the angle of rotation
  angle += 1.0f;
  if (angle > 360) {
    angle -= 360;
  }

  glutPostRedisplay();

  // 10ms
  glutTimerFunc(10, update, 0);
}

int main(int argc, char** argv) {
  // Initialize GLUT
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
  glutInitWindowSize(500, 500);

  glutCreateWindow("Rotating Rectangle");

  glutDisplayFunc(drawRectangle);

  glutTimerFunc(10, update, 0);

  glutMainLoop();

  return 0;
}