I made a terrible factual error in the previous entry. It has been amended.
World 4-2 takes Mario back into the underground in a level that calls back to World 1-2 in obvious ways, but does so primarily to throw you off-guard and hoodwink you.
In fact, the general layout of World 4-2 strongly resembles World 1-2, if that world’s layout had been broken up by pits and chasms. The opening of the stage requires some of the most precise jumping yet, with medium-sized openings surrounding narrow columns. This portion of the level lacks any active hazards, so you have time to focus on making pinpoint jumps without external stressors.
There’s only new element to contend with in this stage, and it’s nothing as nasty or unexpected as Lakitu or the Hammer Bros. For the most part, we simply see familiar elements remixed in more dangerous ways. For example, the first power-up is hidden in a random block after the introductory pits; if you miss it, the next opportunity to upgrade your powers comes with a set of Question Blocks adjacent to a pit. It’s set so that if it produces a Mushroom, that Mushroom will slide right into the pit. You don’t have time to jump up and catch the Mushroom from behind, so your only means of snatching it is to jump over the pit and catch it in midair.
This isn’t a new trick, but its most notable previous appearance was in World 1-2 with the 1UP Mushroom that appeared from the ceiling. That was an optional hidden goody, though, whereas this is a more basic power-up in plain sight. Again, World 4-2 echoes World 1-2 with a greater challenge level. Advanced maneuvers that used to net you rare bonuses now come into play for fundamental play.
And, of course, if you remember World 1-2, you’ll recall the Warp Zone secret in which you could ride a platform up to the top of the screen and run along the ceiling. The same trick works here, though you need to climb up to the ceiling a bit sooner and leap a large gap with a downward-moving elevator. Still, just as you could find a warp zone hidden at the end of World 1-2, there’s one here as well.
Except… there’s only one pipe, and it only lets you skip ahead two levels. What a rip-off!
No, the secret to true warp power lies elsewhere in the level — before the up elevator, in fact. By hitting two invisible bricks, you can create a small stair-step that lets you punch a brick high above the ground to produce a rising vine that takes you out of the underground. This is far more deviously hidden a secret, since it’s a two-step process (find invisible bricks; use invisible bricks to reveal vine), and it requires a touch of curiosity. There are no enemies on this side of the pipe to provoke you into jumping the way you did at the start of World 1-1. Instead, your only clue here is that those two bricks seem like a tantalizing way to access the ceiling yet are too high to reach with a normal jump. You could potentially leap from the descending elevator, but even that’s a tough jump to pull off.
It’s unusual in this game for objects to break from the basic design of the stage layout for no reason, so this aberration should help entice you to puzzle things out. And if you don’t figure it out, well hey, it’s not essential. You can still beat the game through the normal route.
The vine leads you to what appears to be a World x-3 stage in miniature. Apparently there’s stuff above the underground stages, if only you could reach it.
Past the mushroom platforms (and no hazards), you’ll find the real prize: The true Warp Zone, which can take you all the way to World 8-1. But that would be cheating, so we’re going to continue traversing Super Mario Bros. the hard way.
A pipe at the end of the stage leads to World 4-3, should you forego the multiple opportunities to leap ahead to advanced stages. And here were see the level’s one new hazard: Buzzy Beetles, aka that weird round thing from World 3-4.
Buzzy Beetle is basically the inverse of the Spiny: Where Spinies’ spiked shells make them invulnerable to Mario’s basic attack technique, jumping, Buzzy Beetles can’t be harmed by his advanced skill, fireballs. Their shell simply soaks up his attacks, the same as if the fireball had bounced into a wall. Like Koopa Troopas, they’ll retreat into their shell if you jump on them, which allows you to kick them. But here in World 4-2, most of the Buzzy Beetles you encounter occupy narrow spaces with walls on either side. If you kick one in these situations, you’re creating a death trap for yourself as they’ll begin bouncing back and forth at high speeds. The best tactic for Buzzy Beetles is one of avoidance.
Elsewhere in the game, Buzzy Beetles appear in more varied areas in combination with other enemies, but here they appear primarily in these setups so you can get a feel for their behavior and invulnerabilities in isolation — and, once you learn that Mario can’t fry them, you can more easily skip past them.