The second half of Super Mario Bros. kicks off with a devastating tease: A level where three different enemy groups appear to almost, but not quite, allow you to earn a 1UP by kicking Koopa shells. The last group even demands a touch of finesse to not-quite-acquire the precious prize of a 1UP; the kickable Koopa appears after a trio of Goombas, so you need to jump over the little guys and kick the shell left, where it’ll bounce off a wall and carom right for you to pursue after hopping over it on the rebound. But no matter; these critter clusters are only worth 8,000 points, max.
The notable new inclusion in World 5-1 comes in the form of Bullet Bills, an infinitely respawning new danger that straddles the line between standard enemy and scenery hazard. Bullet Bills (at least in this stage) can only appear upon being fired from a “blaster,” a cannon mounted at fixed points. Most blasters can fire Bullet Bills either left or right, so even after you’ve passed one you’re not necessarily safe — it can just as easily shoot you from behind. Bullet Bills can be fired endlessly from each blaster, but unlike other fixed-position and/or respawning foes like Podooboos and fire bars, you can “kill” a Bullet Bill by jumping on it. They are, however, immune to fire, a fact hinted at by the way they share a color scheme (and, heck, even alliterative names in the English version) with Buzzy Beetles.
This stage contains three blasters, all of which appear fixed to the ground, and all of which are aimed at the height of Mario’s head. You can very easily duck each Bullet Bill — or, if you’re standard Mario, simply run right beneath it. To make things even easier, the first blaster only fires if you’ve collected the Starman that precedes it. As with the debut of the Hammer Bros., the game extends an olive branch here by giving you temporary invincibility before a new foe takes its bow. But if you skip the Starman, the blaster remains inert, leaving you to puzzle over its function. With Starman in hand, though, a bullet comes screaming out at Mario, which he then knocks out by running face-first into it. You get to see the function of the blaster and the movement pattern of the Bullet, but from within a wreath of safety.
A new trick for the pipes here, too: For no logical reason, you’ll encounter a pipe hanging in mid-air. This should be your clue that something about it is weird, and sure enough, it leads to a bonus coin room before disgorging you in front of a blaster that fires Bullet Bills with no regard for your state of invincibility.
Holy cow, this level. With World 5-2, Super Mario Bros. manages to throw almost every one of its tricks to date into play, and it features so many secrets that you literally cannot see them all in a single runthrough. Nearly every foe, every scenario, and every hazard introduced so far comes into play here. All it needs is Lakitu, Bowser, and a fire bar and the whole thing would be complete.
The world opens with a reprise of World 5-1′s new element, the Bullet Bill. Its blaster is mounted at the top of a staircase, so its opening salvo sails clear over Mario’s head unless you recklessly leap into action without watching for what’s ahead. This is clearly just a warning shot.
Beyond the blaster you encounter a spring, which sends you over a pit and onto some elevated rows of bricks. As we’ve seen before, it’s easy to use the spring to reach the top of the bricks, but nothing is up there; in order to make the most of this situation, you need to finesse your way onto the lower row, which allows you to grab a power-up.
After that comes the first of four Hammer Bros. in the stage. If you’re lucky enough to be holding a Fire Flower at this point, it’s pretty easy to dispatch this guy. If not, though, you’ll find him much harder to deal with as he patrols a staircase. This gives him the high ground and puts Mario at a distinct disadvantage, as you have to clear the Hammer Brother by leaping from below, hoping you don’t sail into his projectiles and that he doesn’t make a big jump while you’re above him.
Beyond here, though, you have three different paths to choose from. The first you find by ducking into the pipe shortly after the Hammer Brother. This takes you underground, but not to cavern; instead, you’ll come out in an underwater passage where you can collect coins while dodging Bloobers and Cheep-Cheeps. This is a low-reward choice with moderate difficulty — though naturally it’s much less difficult if you’re Fiery Mario and can fry the Bloobers.
The second choice is simply to dash straight through the level. Taking this route, you’ll have to contend with three more Hammer Bros., a Bullet Bill blaster, Buzzy Beetles, and other threats. There are shockingly few benefits to this course, with no power-ups and only a handful of coins between the pipe leading to the underwater section and its exit. In other words, this is high risk, low reward — the most dangerous route through World 5-2 by far.
The best route, on the other hand, comes shortly after bypassing the pipe leading into the water. Hop over a broken staircase and take out a Hammer Brother and you’ll find a hidden Question Block shortly after his stomping grounds. Use that block as a step to hit a block near the top of the screen and you’ll spawn a vine, which leads to a path in the clouds where you can collect more than three dozen coins. Not only that, but when you drop from the sky you’ll also have bypassed the final pair of Hammer Bros.
There’s an interesting little bonus once you drop from the clouds: A pair of extremely low bricks that contain a hidden multi-coin block adjacent to a power-up. Standard Mario can simply run beneath the blocks to collect their contents, but Super Mario has to do a walking duck to squeeze beneath them.
The remainder of the level feels more or less like any other overworld stage, with the caveat that the ground has grown increasingly unreliable. Pits break up the landscape, up to and including the final staircase before the flagpole. Overall, World 5-2 sets the tone for the remainder of the game: Lots of familiar material and dangers, but constantly arranged in ever more devious configurations.