Cheat: Unlimited 1-ups

Are you one of the few gamers (like me) who could use as many 1-ups as possible in Super Mario Bros.? Here's how to get unlimited 1-ups; just don't go over 100 or it'll be Game Over: Go to World 3-1 and turn into Super Mario. At the staircase before the end flag, notice the two turtles coming down. Jump over the first one and jump on the second one. It should hit the star and bounce back. Keep jumping on it to keep yourself up. As long as you don't hit the ground, each consecutive bounce will unlock a 1-up.