1. void setup() {
2.   size(500, 500);
3.   smooth();
4. }
5. void draw() {
6.   translate(width/2, height/2);
7.   background(255);
8.   Triangles(0, -200,
9.   173, 100,
10.   -173, 100,
11.   7);
12. }
13. void Triangles(int x1, int y1, int x2, int y2, int x3, int y3, int level) {
14.   fill(255, 2, 2);
15.   noFill();
16.   triangle(x1, y1, x2, y2, x3, y3);
17.   if (level > 1) {
18.     level -= 1;
19.     fill(2, 2, 255);
20.     Triangles ( (x1+x2)/2, (y1+y2)/2, x1, y1, (x3+x1)/2, (y3+y1)/2, level); //
    
21.     Triangles (  x3, y3, (x2+x3)/2, (y2+y3)/2, (x3+x1)/2, (y3+y1)/2, level ); //
    
22.     Triangles (  x2, y2, (x2+x3)/2, (y2+y3)/2, (x2+x1)/2, (y2+y1)/2, level ); //
    
23.   }
24. }

/**
 * Sierpinski Triangle (v2.0)
 * by Chrisir (2013/Jan)
 *
 * http://forum.processing.org/topic/recursion-basic-learning-topic-adapted-to-triangles
 * http://studio.processingtogether.com/sp/pad/export/ro.98v-TD6NKBKOY/latest
 */

void setup() {

  size(500, 500);
  noLoop();
  noFill();
  smooth();

  stroke(#0000FF);
  background(0300);
  translate(width>>1, height>>1);

  Triangles(0, -200, 174, 100, -174, 100, 7);
}

void Triangles(int x1, int y1, int x2, int y2, int x3, int y3, int level) {

  triangle(x1, y1, x2, y2, x3, y3);

  if (--level != 0) {
    Triangles( x1+x2>>1, y1+y2>>1, x1, y1, x3+x1>>1, y3+y1>>1, level );
    Triangles( x3, y3, x2+x3>>1, y2+y3>>1, x3+x1>>1, y3+y1>>1, level );
    Triangles( x2, y2, x2+x3>>1, y2+y3>>1, x2+x1>>1, y2+y1>>1, level );
  }
}

I've never seen code like what you have inside the if statement. I'm assuming thats the same as saying level -= 1 though. Is that right?