Code to draw a Christmas tree --- (cool flashing)

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#define PI 3.14159265359
float sx, sy;
float sdCircle(float px, float py, float r) 
{
	float dx = px - sx, dy = py - sy;
	return sqrtf(dx * dx + dy * dy) - r;
}
 
float opUnion(float d1, float d2) 
{
	return d1 < d2 ? d1 : d2;
}
#define T px + scale * r * cosf(theta), py + scale * r * sin(theta)
float f(float px, float py, float theta, float scale, int n) 
{
	float d = 0.0f;
	for (float r = 0.0f; r < 0.8f; r += 0.02f)
    d = opUnion(d, sdCircle(T, 0.05f * scale * (0.95f - r)));
 	if (n > 0)
    for (int t = -1; t <= 1; t += 2) 
	{
		float tt = theta + t * 1.8f;
    	float ss = scale * 0.9f;
    	for (float r = 0.2f; r < 0.8f; r += 0.1f)
		{
        	d = opUnion(d, f(T, tt, ss * 0.5f, n - 1));
        	ss *= 0.8f;
        }
    }
 
  return d;
}
 
int main(int argc, char* argv[]) {
  int n = argc > 1 ? atoi(argv[1]) : 3;
  for (sy = 0.8f; sy > 0.0f; sy -= 0.02f, putchar('\n'))
    for (sx = -0.35f; sx < 0.35f; sx += 0.01f)
      putchar(f(0, 0, PI * 0.5f, 1.0f, n) < 0 ? '*' : ' ');
}