World 1-A (New Super Mario Bros.)

World 1-A is the only optional level in World 1, and subsequently, of New Super Mario Bros..

Layout
First, the player has to go down the Warp Pipe, and the player will see an underwater world. Also, a ? Block with a power up can be found. At this point the screen will scroll automatically: that means Mario will be crushed by solid obstacles if he was hit with that at the most left of the screen. Sushis, will appear at both the top and bottom of the screen, two each time. If it is hit by one of Fire Mario's fireballs it will be defeated quickly.

The player can find a P-Switch while swimming along this level. If the player hits it, it will produce Silver Coins between bouncy obstacles. Then, by going high as possible, the player can grab the first Star Coin. From there Mario will go right, entering the pipe leading upwards, appearing near the second Star Coin.

When entering the underwater world again, take up the random Power-up Block while avoiding the Cheep-Cheeps. The player has to dodge the Sushis coming from the left and the can go through a Red Coin Ring to get red coins. The Sushis will now switch back to attacking from the right, but what makes difficult is the current of bubbles from pipes; there's also a silver coin challenge for the player to try.

The player has to swim right as soon as the Star Coin appears above, grabbing the Star Coin, followed by either ducking to avoid the incoming Sushi or swim back out quickly. There's a pipe that leads to the next Star Coin. Going back out the pipe, the player has to swim past the last few Sushis and head up the pipe, going forward to jump onto the flagpole to end the level.

Star Coins

 * Star Coin 1 - On the top of the level it will be guarded by invisible blocks on the bottom, so approach the coin form the left or right side.
 * Star Coin 2 - Right after the first Star Coin is a pipe. Take it and the bro will be transported above ground where the second coin resides.
 * Star Coin 3 - Mario or Luigi will have to maneuver themselves around a stone structure to the right opening to obtain the final coin.

Enemies

 * Cheep-Cheep
 * Sushi