The original BOXBOY! trilogy proved to be one of the quiet triumphs of the 3DS era. These unassuming puzzle-platformers might have lacked the visual fireworks or the 3D gimmicks of some of their contemporaries, but they more than made up for that with a fresh concept and rock solid level design.

We're delighted that HAL Laboratory has seen fit to give its unsung hero a chance to shine on Switch. BOXBOY! + BOXGIRL! is no flashier than it's ever been, but it has expanded in scope by a fair amount. With 270 stages and a series-first two-player mode, this is the biggest and most fully-featured entry yet.

Regular series protagonist Qbby is here joined by Qucy, who serves as both a selectable companion in the single player story and as a second character in the aforementioned co-op mode. Otherwise, this is BOXBOY as we've come to know and love it. The idea is to guide our square protagonist through each 2D level, bypassing traps and ideally collecting all of the crowns that are dotted around.

While Qbby and Qucy can run and jump like your average platformer character, their main power is the ability to spawn clusters of boxes that look like they've dropped out of a Tetris game. At their most basic, these abstract shapes can serve as bridges across spiky pits or steps to take you to higher ground.

Pretty soon, though, HAL starts mixing mixing things up with new mechanics. You'll learn how to use a line of boxes as a grappling hook, a pogo stick, a shovel for digging, and a shield against harmful laser beams. They can be used to activate switches, or to form spring-loaded moving platforms.

This steady unfurling of abilities almost reminds us of a Metroidvania, though the game's rigidly linear progression system and self-contained levels put paid to any further comparisons. Rather, this is simply a puzzle-platformer that's never content to rest on its laurels or maintain the status quo. This is reflected in additional flourishes like a bonus balloon-popping mode that puts your box-forming prowess against the clock, or a character customisation system that treats our heroes' simple features as interchangeable cosmetic components.

It's true of the game's difficulty too. After a pretty easy introduction, the game ramps up its demands on you. It's often simple enough to find your way to the level exit, but doing so within the box limit for an optional bonus score is the real trick. Meanwhile, figuring out how to reach some of those crown collectibles will keep you scratching your head for far longer than you might imagine.

What makes this multi-layered depth and challenge feel so incongruous is BOXBOY! + BOXGIRL!'s radically stripped-back style, which has barely been embellished at all since 2017's BYE-BYE BOXBOY!, or even the original BOXBOY! for that matter. The characters of this world are formed of scarcely more than a few black lines, with dots and dashes for facial features and limbs.

That's not to say that BOXBOY! + BOXGIRL! is devoid of personality, you understand. It's HAL Laboratory, don't forget, that made us fall in love with a pink balloon in the form of Kirby, and the developer hasn't lost its canny knack with expressive animation and jolly ditties.

In BOXBOY! + BOXGIRL!'s co-op mode, HAL has given its series a whole new dimension. Playing with a partner suits the simple mechanics of the game down to a tee, to the point where it feels like the mode must have been baked into the series at the point of conception. If you've played and enjoyed the co-op puzzling of Death Squared, you'll almost certainly get some similar kicks out of this.

This isn't a perfect package by any means. While we dig the BOXBOY aesthetic, there's no doubting it was built with a low-powered mobile device in mind. Blown up on a modern TV, it looks and feels somewhat spartan. Should HAL Laboratory have done more with the Switch's extra power to really push the aesthetic to the next level? Maybe.

It could certainly have tightened up the controls a little. There's a persistent wallow and a sense of lag to Qbby and Qucy's movement and it remains tricky to judge the jumping and throwing physics even several hours into the game. Fortunately there's a generous and frequent checkpointing system that lets you retry each individual obstruction, and you're not penalised for doing so come the end-of-stage tot-up.

Sluggish controls and a brutally minimalist aesthetic do little to blemish the overall BOXBOY! + BOXGIRL! experience, however. It remains a distinctive and deceptively layered puzzler, while the fact that you can now bring a partner in on the fun makes this the best BOXBOY yet.

Conclusion

Bigger and more fully featured than ever, BOXBOY! + BOXGIRL! marks a high point in this quirky puzzle-platformer series. It's not perfect - the stripped back aesthetic and lethargic physics won't be everyone's cup of tea - but fans of co-op puzzlers, in particular, should investigate pronto.