int XYsafe(int x, int y) {
  if ( x >= LED_WIDTH) return 0;
  if ( y >= LED_HEIGHT) return 0;
  if ( x < 0) return 0;
  if ( y < 0) return 0;

  // Invert y
  y = LED_HEIGHT - 1 - y;

  if (y & 1) x = LED_WIDTH - 1 - x;

  // Invert x
  //x = LED_WIDTH - 1 - x;

  return y*LED_WIDTH+x;
}

void clear() {
  for ( byte y = 0; y < LED_HEIGHT; y++) {
    for ( byte x = 0; x < LED_WIDTH; x++) {
      leds[ XYsafe(x, y)]  = CHSV((16*y)+(47*x), 255, 42);
    }
  }
}

inline double sines(double x, double y) {
  return ((cos(x) * sin(y)) * 0.5) + 0.5;
}

inline double basefield(double x, double y) {
  return (cos(x) * sin(y) * cos(sqrt((x*x) + (y*y))));
}

inline double addmod(double x, double mod, double delta) {
  x = x + delta;
  while( x >= mod ) x -= mod;
  while( x <  0.0 ) x += mod;
  return x;
}

inline double addmodpi(double x, double delta) {
  return addmod(x, 2*PI, delta);
}