Just keep rolling. And rolling. And rolling.

At its core, iO is a fairly simple game; as a wheel, solving each puzzle means reaching moving through a green portal. In your arsenal are two – yes, only two – mechanisms to solve each puzzle: moving horizontally and adjusting your size. While this may initially seem limited, controls still manage to feel intuitive. As a result, it offers the player agency in how to move and grow or shrink to solve each level. Levels can often be completed in numerous ways, and there’s a smug satisfaction felt when finding a much more inventive (and efficient) route to the finish.

“At its core, iO is a fairly simple game; as a wheel, solving each puzzle means reaching moving through a green portal.”

It quickly becomes apparently that movement and size adjustment yield their own set of conditions. During the introductory stages, momentum and weight become key factors in how levels are approached. Increasing in size while going down a hill allows for more speed, while shrinking at the end of a ramp sends you soaring. Gathering enough momentum on a spiral track allows you to continue gripping the track even when it’s above you. While the rules of the world are introduced early on, the game leaves it to the plethora of levels – over 200 – to utilize these mechanics in interesting ways. Before long, I was shifting between sizes to climb stairs and rocketing off ramps with blazing speed. Knowing that the game was also released on mobile devices, I was very pleased to play using physical buttons as it allowed for the precision that I wanted.

Fortunately, level design is generally quite impressive in iO, with levels starting off slowly to practice the basics before introducing new design elements. After some progression, a variety of obstacles are introduced independently before appearing together in more complex levels later on. Moving platforms and red patches of land causing instant death impede your progress, and movable blocks and gears require precision to set them in the ideal location. Given that most levels are generally quite short, death doesn’t feel like a punishment, and the designated restart button is always within reach. Medals are awarded based on your time, motivating players to replay levels and find creative ways to shave fractions of seconds off of their times.

A welcome decision by developer Gamious is the option to have all levels available right from the beginning. Since most levels rely on a significant amount of trial-and-error, getting frustrated is not an uncommon experience. I was also quite surprised at the rapid difficulty spike that I encountered in some levels, only to find a simple level following directly after. Having the freedom to skip a level and continue progressing certainly alleviates some of that frustration, but the fact that the difficulty of a few select levels is so far beyond that of the ones before and after remains a bit perplexing. On a more positive note, entering each new level continued to pique my curiosity, and the sleek, minimalist aesthetic of each level was always pleasant on the eyes.

One other notable grievance I encountered was the camera’s persistence in zooming in too far. To allow for greater precision when squeaking through tight corridors, shrinking forces the camera to zoom in, forcing the majority of the level off-screen. For simpler level designs this isn’t an issue, but it can often disorient in moments when it shouldn’t, resulting in an undeserved death and a trip back to the beginning of the level. I often found myself starting a level and memorizing my desired path before restarting the level to reset my time clock. Some of the most advanced levels take advantage of that level blindness in clever ways, but in the overall package it yields mixed results.

“Though far from revolutionary, iO is a simple, yet intuitive puzzler that is sure to dig its hooks into fans of the genre looking for a unique challenge.”

Difficulty spikes and an occasionally frustrating camera aren’t enough to detract from all the physics-based puzzling goodness that iO offers, however. Shrinking and growing on demand is a fun mechanic that makes the game stand out from the variety of other like-minded games out there. On top of that, the sizeable amount of content that the game offers will keep you busy long after you overcome any frustrations you might have. Cross-buy functionality also means that you receive a version of the game for PlayStation Vita, which is certainly an added perk. Though far from revolutionary, iO is a simple, yet intuitive puzzler that is sure to dig its hooks into fans of the genre looking for a unique challenge.

iO is available on PC, PlayStation 4, Xbox One and PS Vita. We reviewed the PS4 version.
iO Review
Growing and shrinking is a charming mechanicCreative level designsLoads of content
Occasionally frustrating cameraRandom difficulty spikes
7Overall Score