Draw the overlay describing resources.

def draw_overlay(self, surf):
    """Draw the overlay describing resources."""
    obs = self._obs.observation
    player = obs.player_common
    surf.write_screen(
        self._font_large, colors.green, (0.2, 0.2),
        "Minerals: %s, Vespene: %s, Food: %s / %s" % (
            player.minerals, player.vespene, player.food_used, player.food_cap))
    times, steps = zip(*self._game_times)
    sec = obs.game_loop // 22.4  # http://liquipedia.net/starcraft2/Game_Speed
    surf.write_screen(
        self._font_large, colors.green, (-0.2, 0.2),
        "Score: %s, Step: %s, %.1f/s, Time: %d:%02d" % (
            obs.score.score, obs.game_loop, sum(steps) / (sum(times) or 1),
            sec // 60, sec % 60),
        align="right")
    surf.write_screen(
        self._font_large, colors.green * 0.8, (-0.2, 1.2),
        "FPS: O:%.1f, R:%.1f" % (
            len(times) / (sum(times) or 1),
            len(self._render_times) / (sum(self._render_times) or 1)),
        align="right")
    line = 3
    for alert, ts in sorted(self._alerts.items(), key=lambda item: item[1]):
      if time.time() < ts + 3:  # Show for 3 seconds.
        surf.write_screen(self._font_large, colors.red, (20, line), alert)
        line += 1
      else:
        del self._alerts[alert]