"Zen" is an overused word on the App Store. It appears, mostly wrongly, in the titles of a pinball game, a fighting game, numerous puzzle games, and even a war game. The word refers to an offshoot of Buddhism that emphasises the value of meditation - which means that Color Zen is using it wrongly too.

You can get through the first 20-stage chapter in a fairly meditative state, and you'll be able to return to that state from time to time as you cruise or fluke your way through the game's easier stages, but you'll need to concentrate pretty intensely when the going gets tough, and you won't feel remotely relaxed.

While it has a familiar minimalist aesthetic, Color Zen is unlike another other puzzle game you've ever played.

In each stage there are shapes of various colours, some of which you can move and some of which you can't, and around each stage is a coloured border.

When you bring two shapes of the same colour together it fills the screen, swallowing up any other matching shapes that are lying around. The aim of the game is to finally fill the screen so that it matches the border without leaving any other colours behind.

This is easy enough at first - you just note the colour of the border and make sure you bring those shapes together last. Even when there are nested shapes that seem to be dictating a certain approach, you almost always stumble across the solution on your first attempt without giving it any thought.

It's a gentle introduction to the mechanics of the game, and it may leave you wondering where the challenge is supposed to lie.

Colour me bewildered

Then, in quite an un-Zen-like fashion, the challenge shows up towards the end of each chapter and gets you in a figurative headlock, overcoming you with a reason-defying arrangement of nested shapes that you need to carefully unpick.

As you make your way through the hundred stages the game gradually introduces more elements - white shapes that turn the screen the colour of the shape they collide with; black shapes that disappear along with the shape you pushed against them; multiple shapes within shapes; shields that you activate by double-tapping them.

This means that you're increasingly unlikely to solve stages with ease or dumb luck, and it's here that the children will be separated from the grown-ups.

Who are the children? They're the players who relied on luck and experimentation, feeling vaguely amused by the bouncing shapes but largely unfulfilled because they knew, deep down, that they didn't always deserve their victories.

Who are the grown-ups? They're the players who were able to look at a bewildering array of shapes and colours and work out, not through luck or intuition or pattern-recognition but through sheer IQ test-blasting visuospatial brainpower, exactly what order they had to dispatch them in.

Before buying Color Zen you need to ask yourself whether you're a child or a grown-up.

Color Zen is certainly original, and it'll keep you playing for a long time assuming you're sufficiently interested in its central mechanic. But you'll have to be a gifted puzzle gamer to remain in a meditative state throughout.