void drawRects(int step){

  SDL_RenderClear(renderer);

  int cols = matrix[1];
  int rows = matrix[0];
  int colWidth = ((600-5)/cols)-5;
  int rowHeight = ((300-5)/rows)-5;

  for(int i=0; i<rows; i++) {
    for(int y=0; y<cols; y++) {
      SDL_Rect rect;
      rect.x = (colWidth+5)*y+5;
      rect.y = (rowHeight+5)*i+5;
      rect.w = colWidth;
      rect.h = rowHeight;

      if(pattern[i][y] == 1) {
        SDL_SetRenderDrawColor(renderer, 50, 255, 50, 255);
      } else {
        SDL_SetRenderDrawColor(renderer, 50, 50, 50, 255);
      }
      SDL_RenderFillRect(renderer, &rect);

      if(step == y) {
        SDL_SetRenderDrawColor(renderer, 200, 200, 200, 255);
        SDL_RenderDrawRect(renderer, &rect);
      }

      SDL_SetRenderDrawColor(renderer, 100, 100, 100, 255);
    }
  }

  SDL_RenderPresent(renderer);
}