Another platforming adventure is about to begin! Mario is ready to set out to defeat Wario and reclaim his castle, but it appears that the entrance to the world itself is crawling with enemies. It's time to challenge your first level!
The Mushroom House[edit]
Take your time to get used to the controls. Walk forward and you'll encounter your first enemy, the goomba. These common walking mushrooms can easily be defeated by jumping on top of them, but expect to see a lot more of them in the future. You will also encounter a koopa troopa. Unlike the goomba, stomping them will make them retract into their shells, which you can kick as a projectile to take out other enemies. Be careful, as the shell can also hurt Mario!
In a question mark block not far from the koopa, you will find your first power-up, the Super Mushroom! Collecting this mushroom will make Mario grow to twice his size, letting him break blocks and use the drill attack, which can let Mario break blocks from above and instantly defeat koopas. Go right a bit more and you'll come across a pipe. Press down to travel through the pipe, which will drop you off in a secret chamber full of coins! Collect all the coins and return to the surface using the second warp pipe.
Further right, you'll encounter a paragoomba. Stomp on these once and they'll revert to a regular goomba. You will also meet another recurring Mario enemy, the pirahna plant. These overgrown flora live inside sewer pipes and emerge to snag any potential prey. You can't jump on them to defeat them, so just jump over them. Continue forward, and you'll come across a Heart and a Star. The Heart will give you an extra life, while the Star grants you invincibility, so be sure to grab both.
You will soon see a bell which acts as a checkpoint. After you ring the bell, you'll start from that point after you die, so you needn't worry about losing all your progress. You may also be able to get a Fire Flower in another question mark block, as long as you're big Mario. With it, you can take a total of two hits before dying, as well as being able to throw fireballs. You can now scorch koopa troopas and pirahna plants, killing them in one hit.
Continue going forward, and you will come across a 1-up stuck under a bunch of bricks. You need to use the drill attack to break through these blocks, which can be performed by pressing 
in midair. You will also come across some blocks that can only be destroyed by fireballs, so keep that in mind the next time you see them. After that, the end of the level should be in sight. There is another bell you can ring, though you must jump on top of a series of platforms just to reach it. If you manage to ring it, you'll be able to enter a bonus minigame after exiting, letting you get a power-up, a 1-Up or even three extra lives!
A frantic run[edit]
Now that you're accustomed to how most of the game is going to be, you can start beating one of the six zones. Before you do that, you can try one extra level to get a free fire flower and some extra lives. There is a single level west of the castle that you can directly challenge, which will put you into a forced scrolling stage. There are nothing but goombas in this level, and you don't have to make any ricky jumps, so it is actually quite easy. To the left of the sole non-question mark block in the level is a hidden block containing a Star, which you can use to run over goombas and get up to two extra lives. You can beat this level again whenever you like, and it is recommended that you do so every time you start the game just to power yourself up and get more lives.
Into the giant tree[edit]
You've passed your first two levels, but there are still many more challenges ahead of you. You can attempt to beat any zone at this point, but a good place to start would be the Tree Zone. Go left until you see the giant tree and walk up to it to enter.