Super Mario World/Donut Secret 2

Donut Secret 2 can be accessed using the secret exit in Donut Secret House.
 * It's an underground level, made mostly out of ice. There are lots of Spike Tops and Koopas.
 * The first coin block contains a growing coin line that can move in any direction. The number of coins you collect from it will vary. It will stop if it hits a wall or goes off the screen. It will also stop if enough coins appear from it.
 * There is an invincibility star above a hidden vine above a spring. Collect it. If you proceed quickly enough, another ? block will contain another invincibility star. If you are not invincible, it will just contain a coin.
 * After clearing two Jumpin' Piranha Plants a green pipe will lead to an above ground bonus level. You can pass that level with or without the P-Balloon that's inside the ? block. With the balloon you will be able to get more coins.
 * The last drop-off provides the chance to collect an extra life by jumping on all the flying koopas. It's safer if you have a cape. The finish line awaits!