Puzzle games are a difficult genre. Because of the relative simplicity of devising them, there’s a lot out there. iO is a pretty simple game at the root, as well, but there’s some great complexity lurking underneath. Playing iO consists of one simple goal: roll a ball to the portal to complete the level. The ball has two control mechanisms: left-right movement, and size adjustment. Combining these two relatively simple controls during play is tricky, and you’ll have to learn to make changes on the fly if you hope to succeed.
iO opens up the way that many puzzle games do, with a set of simple introductory levels that introduce the basics of these mechanics. Different types of obstacles, including moving platforms, movable blocks and gears, and wild ramping curves are introduced one at a time until being combined in later levels. Overcoming these obstacles, especially when presented with more than one, means shifting size and direction constantly. While a larger ball is heavier and gains more traction, shrinking gets you through tight spots or allows you to soar into the air to reach far-off areas.
Each level in iO features the same goal: a green portal. Reaching this, however you do it, is the only thing that matters. Some levels have straightforward paths, but others present more twisting challenges that may take multiple attempts to unravel. Falling into lava or flying off of the stage result in “death”, forcing a restart; you can also choose to restart at any time if you find yourself stuck, which happened to me relatively infrequently. Aside from the basic task of reaching the end, medals of bronze, silver, or gold may be awarded if you complete levels quickly enough.
iO, with its simple aesthetic and minimal controls, presents a very simple, approachable game. My seven year old asked for a turn while I was reviewing, and got through several of the earlier puzzles. It doesn’t take long, though, to throw in some truly challenging points to keep things interesting. Fortunately, there’s no need to unlock levels as you go on. You’re given free reign to play whichever level you’d like, in any order. There’s clear advantages to working your way up the ladder, of course, but if you come across something that you can’t get past, you can move on to return later.
All in all, iO puts together a simple but effective package that presents a wide skill range of available puzzles. With plenty of variety to the obstacles you’ll face, there’s lots to do no matter which type of puzzle you’re best at. Levels can be played and replayed, allowing you to hone your skills and move on to tougher challenges or new obstacles. While I’m not entirely sold on the normal $9.99 retail price on Steam, there’s currently a 50% sale with a much more palatable (and recommendable) $4.99 tag easing the choice. If you’re a fan of unique, interesting physics-based puzzles, you should be trying iO.