Apple has set the Nano back on track with the thinnest, lightest design yet, and has features that are hard to ignore.

Design
Apple's most popular music player has undergone yet another extreme makeover. In contrast to last year's compacted design, the Nano has been stretched back to the candybar footprint of its first and second generations. That doesn't mean that specs have gone backwards, however. The size and resolution of the display is the same as the third-gen's version at two inches (5.1 centimetres) and 320x240 pixels, but it's been rotated 90 degrees to fit the form factor. The Nano is now a few hairs thinner at 6.2 millimetres, and almost 12 grams lighter at a feathery 37g. It's available in eight vibrant metallic colours in all three capacities — a refreshing change from previous generations which offered a limited colour range for each variety of player.

As with the new Touch, things have been smoothed out since last year. The Nano now sports an elliptical cross section, meaning the screen has a slightly curved glass overlay. This makes the display slightly more reflective than previous models, but it's not a big deal and shouldn't interfere with photo viewing or video watching.

Instead of sporting a reflective — and scratch-prone — back, the Nano is wrapped in one piece of brushed aluminium. It's a more practical design for those who chuck their players in a bag or pocket with a ring full of keys nestled up close.

The placement of the scrollwheel seems very low due to the height of the player and its vertical screen orientation. The combination of this and the thinness of the wheel can make your thumb feel a little squished and awkward when navigating through lists. On the plus side, the hold switch that got inexplicably relocated to the base of the third-gen player has been restored to its rightful location at the top left.

Features
The split-screen menu that debuted on last year's iPods was pretty-looking, but it also made the text feel cramped — and there was no way to turn the floating images off. For its fourth-gen Nano, Apple offers up a different version. Instead of being vertically bisected, the menu screen displays album covers and images in a strip at the bottom. If that's still too much for you, you can revert to a vanilla text menu by turning off the "Preview Panel" option in the main menu settings. The user friendliness continues with a new font size option, which enlarges all text in the menus.

Cover Flow browsing turned up in the last Nano release, but this time there's an accelerometer involved. Tilting the Nano 90 degrees brings on a parade of album covers organised by artist. Scroll through them speedily and the first letter of each is displayed beneath the whizzing images.

The accelerometer also allows for a rather gimmicky feature: shake to shuffle. As with Sony Ericsson's W910i phone, moving the Nano rapidly up and down causes a random track to surface from the depths of your audio library. As with the W910i, the attribute is cute but largely pointless.

Another software change is the addition of Genius, a playlist-creation feature introduced in iTunes 8. Choose the Genius option when a song is playing and the pixies in the circuit boards will assemble a list of 25 tunes that share the mood of the original. Genius works better on higher capacity Classics and Touches, where there are more songs to choose from, but it's relatively effective on the Nano as long as your tastes don't run to the very obscure.

As with the new Touch, the voice recording feature can't be used without investing AU$48 in Apple's new mic-equipped ear buds. This inclusion of accessory-dependent features can be viewed in two ways: either Apple is being a tease and forcing you to spend more money, or they're being considerate by keeping things simple and assuming that not everyone will want to record audio.

Performance
A perennial complaint about Apple music players has been that for a range that exhibits exemplary design and innovative interfaces, the same level of care is not shown in the sound quality — at least when heard through the bundled basic headphones. Though Steve Jobs acknowledged the grumbles and announced a new set of silicon-tipped ear buds at the iPod media event in September, the Nano ships with the same set of buds that accompanied last year's model. As a result, audio is akin to what we described in our last Nano review: a little humdrum and flat.

Video, on the other hand, looks fantastic. Footage is smooth, vibrant and immersive — well, as immersive as you can get on a 2-inch screen. Being able to view photos in landscape mode — they rotate automatically when you turn the player — cuts down on the "squinting at a postage stamp" factor.

The fourth-gen Nano is the friendliest one yet, with more customisation options, a smudge-free back and a wafer-thin yet sturdy construction. Those who dug its squarish predecessor may get a bit of a shock at the layout, but it's ultimately easier to use than the third-gen release.