The two-dimensional world of classic Mario is the perfect place for 3D. The ground stretches out flat and even. Hills climb upward like staircases. Cliffs and ledges are square, tidy drops that descend forever into nowhere. Overhead, the flat blue sky is interrupted by clouds so solid that Mario can run across them like fluffy white tabletops. The colors are primary and flat, as though they had been filled in by someone using a small box of crayons, and the sunlight shines brightly from overhead.

Super Mario 3D Land looks like a storybook, and the 3D effect provided by the Nintendo 3DS turns it into a pop-up book. Mario has been moving around in three dimensions since the advent of 3D modeling, but I haven’t been able to see him and his world in 3D until now. Instead of the free-flowing landscapes of Super Mario 64 or Mario Sunshine, Nintendo has elected to make Mario’s 3D-display debut in a game that resembles the classic Super Mario Bros. The simple landscape, with its flat contours and staggered layers, is an ideal match for the 3DS’s diorama-like display, where things don’t reach out as much as they recede into the distance.

This straightforward special effect brings a wrinkle to the basic side-scrolling Mario challenge. Until now, Mario’s enemies have mainly confronted him head-on, like the cranky-looking mushrooms that scuffle toward him, or the sofa-sized bullets that cruise through the air. Other threats have always come from above and below, such as the giant blocks that rise and fall, blocking his pathway with rhythmic thwomps.

But now that I can perceive distance in the background, Mario’s threats can also attack him from the side as he runs left to right. The pointed ends of giant spiked battering rams rush forward, their momentum made clear by their growing approach in 3D. Spiked balls on chains swing in and out of the screen as Mario dashes beneath them. These aren’t new obstacles — they just threaten Mario from a new direction.

THE GOOD: The precision required to make Mario run and jump across his obstacle course has often left my palms sweaty as I try to keep the little plumber from plummeting to his doom. But now that I can see how far he might fall, the threat is extra exhilarating. Even more exciting are the levels in which Mario must willingly dive through the air as I guide him, looking over his shoulder as he base-jumps hundreds of feet to land precisely on a waiting cloud, mushroom or enemy.

THE BAD: I’ve never been able to sit still while controlling Mario. During particularly tense moments I find myself leaning in the direction I want him to move, or my hands shudder when I want him to make a trickily timed jump. Unfortunately, the 3D effect turns into blurry double vision if the 3DS isn’t held perfectly straight a certain distance from my eyes. This means that every time Mario gets into a difficult situation, I lose my clear view of him if I allow myself to be caught up in the game’s excitement.

THE BOTTOM LINE: Super Mario 3D Land adds a new dimension to a classic challenge.