"What if you walk along and everything that you see is more than what you see - the person in the T-shirt and slacks is a warrior, the space that appears empty is a secret door to an alternate world?" Miyamoto said to David Sheff, author of the seminal book Game Over. "Perhaps it really is a doorway to another place. If you go inside you might find many unexpected things."
It was surreal, it was impossible, but the Mushroom Kingdom was also more real than other videogame worlds, because you could interact with all of it. There were physical laws, consequences, complex relationships of action and reaction. Mario could bop the turtles (Koopas) out of their shells and kick the shells at other creatures. He could bounce a mushroom by hitting the block underneath it. If he was Super Mario, he could smash up walls. How many games still sell themselves on destructible scenery? Super Mario Bros. had it.
You could transform Mario still further with the fire flower item, which allowed him to shoot (although, typically, not in a straight line - because that would be obvious). But Mario learned never to rely totally on his tools. Like the hammer in Donkey Kong, the items in Super Mario could always be taken away, and he'd be left with only one thing - his jump. Only now, his jump was a weapon.
Defeating enemies by jumping on their heads was a defining feature of Super Mario Bros.; it encouraged you to keep Mario airborne and keep the momentum going. In fact, Mario's iconic move didn't reach its full-fledged form until Super Mario Bros. 2 - the first one, the "true" one, the Japan-only one, known as The Lost Levels in the West.
It was in The Lost Levels that Mario learned to bounce. He could now spring off creatures' heads to reach otherwise inaccessible places, or to keep a chain going. It was an apparently small change, but a crucial one. From the first sequel, the denizens of the Mushroom Kingdom became tools as well as hazards, platforms in their own right; a brilliant reversal of traditional thinking that amped up both risk and reward.
This is classic Super Mario Bros. The series doesn't set puzzles so much as rules to be broken; it doesn't set goals so much as dares. Every level is a series of temptations to make things more difficult for yourself than they need to be, because it's fun, because you want to see what will happen, because it's there.
In this case, however, it was a bit too difficult to start with - or at least, Nintendo's American arm thought so. It rejected the Japanese Super Mario Bros. 2 on the grounds that it was too hard and too similar to the first. Playing it today, it's hard to disagree. Warps that take you backwards are pure cruelty, and requiring you to complete the game eight times in succession to unlock the last four worlds isn't a secret, it's just grind. There were scarcely any new graphics or features (although the mushrooms now had eyes, and the clouds had started smiling).
The Lost Levels didn't take Super Mario Bros. forward, but Nintendo of America's replacement wasn't Super Mario Bros. at all. It was a reskinned version of another game made by Miyamoto and Nintendo's EAD team, a TV spin-off called Yume Kojo: Doki Doki Panic. It involved plucking and chucking smiling vegetables at enemies. Jumping on them didn't even kill them. Mario rode the hapless creatures' backs until he picked them up and hurled them like anything else. Sacrilege.
Super Mario Bros. 2 may have been a bastard, but it was a fine game, and still is. The sub-space zone, a dark mirror world you could enter by conjuring a door which turned vegetables into money, was like something out of a future Zelda. The levels allowed free roaming - yes, even backwards! - and gained a vertical dimension, scrolling up and down clumsily but freeing Mario Bros. of that forced, constricted drive from left to right. Picking up and throwing things was fun.
But... it had a life-meter you could extend, and by default you started a level powered-up, not tiny and vulnerable. It had four playable characters (Mario and Luigi were joined by Toad and the Princess) who were crudely defined to differ from each other. Mario needed items to succeed, his jump neutered again. Super Mario Bros. 2 was polished and interesting, but it was how everybody else did things.