The sharp, minimalist visuals of iO were the first thing that caught my attention when I checked out the Steam Store page. Having seen and played tons of puzzle platformer games I was asking myself if this game would introduce me to new gameplay mechanics I hadn’t witnessed or experienced before. And while we’ve certainly seen specific parts of it before in other games it does actually give us something new, and maybe even something to get excited about.

Having debuted on Ouya (a platform that everyone was excited about when it was first showcased, but once released the interest in it took a nosedive) iO never got the attention that it initially deserved. With the PC release it might still have a hard time getting any attention at all. So many games are released every week that it’s hard to get your game promoted, especially if you’re a small game developer. And it’s especially hard if it’s a fun game as well. Let there be no doubt: this is a fun game and I hope it does well, both commercially and critically.
The setup is simple: get the ball to the end of the level, marked with a portal. The levels are made up of random platforms, these can be horizon and vertical, as well as diagonal. Then there are the platforms that have to be pushed out of the way and tricycles that can get you across fiery (red) platforms that will destroy your ball. Falling down or getting too high up will also destroy your ball. It’s your goal to keep the ball on or between the platforms as much as you can.
But it’s not as simple as getting from A to B. Like a wise man once said; it’s the journey that’s important. And that’s exactly right. That’s because the ball has to increase or decrease in size to get through specific parts of a level. And within a few minutes you’ll learn how to speed up your ball to get to higher parts of a level but you’ll also learn how to blast off so you can jump across a gap. Not only that, but you’ll also learn how to jump, which is actually quite easy once you know exactly what to do (which is usually the case with pretty much anything these days). The keyword is ‘momentum’ which means you have to time your actions. You’ll be repeating levels over and over again because 1) you didn’t know what to do, or 2) because your timing was off. It’s usually 2) that causes the retry.
There are 150 levels to complete and each one you complete can earn you a medal. Can, because taking too long won’t earn you anything but if can complete a level within several seconds or minutes (this, of course, depends on the level) you might be able to earn a bronze, silver or gold medal. The gold medal usually requires perfection. You might not notice this right from the start, but halfway through things can get hard and earning that gold medal might not be so easy anymore.
The controls are easy; a controller works best here but bringing up the menu while in-game can be troublesome. I frequently pushed B to bring up the menu, but because the game wasn’t as responsive in this area as it should be it usually took a little longer. By then I was already rotating the stick and eventually was returned to the main menu or the next level. A small nitpick but still a little flaw in my book.

As I already mentioned in the first paragraph the game uses a minimalist look, meaning everything has a basic shape and there are no backgrounds or background colors. It also uses basic, neon-like, colors like red and blue. It looks pretty in motion and the core of the ball becomes fierier the faster it goes. A little detail that doesn’t add anything to the game itself, but it surely looks cool.
Audio-wise it’s also very minimalist with some decent background music and basic sounds.

You can play this game just for the bronze medals or you can try to finish them all with gold. In any case it should take around 5-7 hours for a quick ‘playthrough’ and for a thorough playthrough it will take you probably double that amount. That’s plenty of gameplay for a game with this price.

iO (still) is a very fun, but sometimes extremely challenging, game that mixes up the genre a tiny bit. Its gameplay mechanics are solid, as are the controls, and its visuals are beautiful and relaxing. If you like to play puzzle platformers then iO is the perfect game for you. Even newcomers to the genre should have a bloody good time with it.
It was a small success on Ouya, but now is the time to make it an even bigger success. Click that ‘Buy’ button, people.

[Rating: 80/100]

After playing the game for about an hour, I can definitely say it's worth buying! The game features O, a small ball which has the ability to get bigger and get smaller. By doing so you increase/decrease your mass, alowing you to gain a lot of momentum when being big, and then transforming that momentum in actual kinetic energy when your smaller. Obviously the game has way too many features for me to discuss right now, so I'll just write down the tops and tips.

Tops:
-Very good graphic design for a game of this genre
-Non-lineair gameplay, so that the game stays fun
-Challenging
-Good music
-Runs very smoothly
-Original
-Plenty of content (150 LEVELS, HOLY SH!T!!)

Tips:
-Perhaps implement a competitive leaderboard (I haven't seen yet, might have missed it) so people can compare their score to others
-Implement multiplayer
-A level editor would be awesome

I definitely recommend you to buy the game, as far as I've seen. If you want to watch some gameplay first, check this video: https://www.youtube.com/watch?v=qbmnky19etk

I rate 8/10, simply a great game.

iO is a clever little game with simplistic and very addictive gameplay.
The goal is to get the ball into the portal. Sounds simple enough on paper, in reality its pretty tricky. You can change your size and that will determine your speed and the rate at which you gain speed, and this is essential part of the gameplay - figuring out the optimal size to achieve a task. There is no time limit on the levels ( all 150 of them !!), but medals are awarded, depending on your speed of completion - the faster, the better. About that, I would love to see a timer inside the level, but maybe that's just me.
The controls are fine, I used keyboard - either WASD or the arrows. The ability to rebind tjem would be a plus, but I didn't feel the need for it at all. The music is abstract and fitting, the sound effects are not that much, but still reasonable.
There is no level progression, you can start from whatever level (out of the 150) you want. There is a trial pack of levels, that plays the role of the tutorial and introduces you to the game mechanics. After that, there are still the occasional hints inside the first few levels, but the game does not hold your hand by any stretch of the imagination. After the first few straightforward levels, you'll need time to figure out the way to complete the level, and then actually execute your plan ;) It's enough to say, the game has a key to instantly reset the level - you will use it a LOT. The trial and error is the way to complete most of the levels for the first time. I really like the steam leaderboards and the ingame medals, as there is always a way to improve with these game mechanics ( it's not set in stone thing like a "jump" - you gradually change your size and speed, so optimal size and time to switch it, is hard to determine).
The only thing I dislike about the game is, that it has the nerve the actually spin up all my hard drives before starting - typical for a KISS release, and really annoying in my opinion.
With the pretty simplistic game graphics and mechanics, a level editor will be a really nice edition to the game at a later stage, allowing the community to go nuts, but for now, I think, trying to ace the 150 levels is more than enough.
The huge amount of levels, steam leaderboards, steam trading cards, addictive gameplay and that price tag ... all of it leads to my wholehearted recommendation of the game!

TL:DR you can check my overview video, where I complete the first level pack :
http://steamcommunity.com/sharedfiles/filedetails/?id=351747382

Imagine a game where the character is just a ball the whole time. A ball that isn't even bouncy and can't jump. Consider how difficult it is to implement any platforming that isn't simply clunky and awkward with such a limitation.
Now let's think about 99% of platformers. How very annoying and limited would they be if they didn't allow changing directions in midair? It is completely unrealistic, yet omnipresent.

I thought about these concepts a lot, and didn't believe it was possible to make a decent game with the mentioned limitations. And yet, here we have iO, and calling it decent would be a huge understatement.

So yes, the character is a ball that can roll clockwise and CCW. You don't simply "move right"; the movement happens because of friction. The ball can also shrink and grow (changing its mass) anytime. Arbitrarily changing mass and angular momentum are the only unrealistic things here; the rest is just physics.

And oh how fun pure physics can be...
As mentioned, rotating allows you to move using friction. The friction also applies to walls and ceilings, allowing you to do not-so-obvious things. Changing mass in mid-air while keeping the momentum lets you change the trajectory (launch yourself). The process of growing in size improves your grip, letting you speed up easier, or... climb some walls! Now, don't forget that you can only grow/shrink so much...
And of course, we also get the more typical features of a physics-based game: There are moving platforms. You can push and interact with things in other ways using friction. Portals: speedy things comes in, speedy thing comes out... but what if the thing can change mass?

The game is almost flawless (if you overlook occasional clipping through objects in rare cases, which doesn't affect the gameplay).
Graphics are very aesthetically pleasing. Won't talk about music, because I rolled with my own.

★★★★★★★★★☆

If you like challenging platform games like VVVVVV, Super Meat Boy, Monkey Ball or Spelunky, you'll love this game. Physics puzzling challenge in his best form!

I'm usually not that much of a platformer person, but I liked the artstyle and music so much that I thought I'd give it a go. And well, the levels are very diverse in what they offer, and I'm having a blast so far. Especially the portal levels are great fun. Getting gold times is quite hard, and the game can be quite difficult as well, but if you're up for a challenge it can be very a rewarding experience :).

Physics platformers, oh how I love breaking you.

Having tons of fun speedrunning this game - It has good physics - good strategies - mechanics/bugs/exploits to abuse - Leaderboards with me #1 on them... What more can I ask for <3

If you like solving puzzles - or have a competitive bone in your body defintely reccommend picking this up and challenging me. Goodluck.

https://www.youtube.com/watch?v=TUv2yjLAdEE

A real hidden gem on Steam this one.
A physics based puzzle platformer with a Tron about it, I will have many sleepless nights trying to get all the gold medal times on this game :(

+ 150+ Levels
+ Simple yet responsive controls
+ Simple yet effective graphic style, reminiscent of Tron.

- Rage inducing if you miss a medal by 0.01 of a second.

a very frustrating game, but in the fun way that makes you keep playing until you've finished the level or until your fingers bleed ;)

Very addictive game. Casual enough to pick up and play whenever you feel like it. Challenging enough to stay fun/rewarding.

Awesome puzzler / platformer! Good for quick sessions, completionists and those who love the puzzle / physics platformers!

This is a fun little game! Wide compatibility and easy to learn but hard to master. There are a lot of these momentum-based puzzle games but this one is easy to look at and the sizing vs momentum mechanic is something we haven't seen in a while! It also hase really abstract graphics and runs on any system (Me using a Macbook Pro 2014 myself, but my old 2008 Macbook takes it as well.)

Dexterity and puzzling combined in one game!
Think Trails Fusion in abstractform and add mind-boggling puzzlelevels.
Some just come naturally and some make you facepalm for hours.
Practice , rethink and master!

Btw, size does matter!

Crazy addictive, this game will keep me busy for hours farming all the gold medals untill my OCD is satisfied :P Good soundtrack too :)

Awesome game. Plays like a charm with very cool unique gameplay and original puzzle elements. Easy in the beginning, but gets harder later on, especially if you're going for gold.

Very nice puzzel game. Fast pasted and beatifull clean art.

An elegant puzze platformer with simple game mechanics at its core that show endless amount of ideas and creativity in its level design.

Very polished!

Awesome.

Addictive. But i need more levels!