You've probably heard of OnePlus. This small smartphone manufacturer from China was founded less than two years ago by a former vice-president of Oppo and set up shop in India late last year. The company uses an innovative invite-based system for distributing limited quantities of its devices while creating hype and a level of demand that far outstrips the supply. The marketing department of OnePlus is run by absolute geniuses.

Soon after launching this year's 'flagship killer', the OnePlus 2 (Review), the company launched a more budget-friendly model, the Rs. 16,999 OnePlus X. Our initial impressions of the device were that it is essentially a smaller OnePlus One (Review | Pictures). Is this all the 'little' OnePlus is about, or is there more to it? Find out in our review.

Look and feel
Initially (and unofficially) referred to as the OnePlus Mini, the X is smaller and easier to handle than either of the company's previous smartphones. Apart from the obvious difference in screen size that dictates the length and width, the OnePlus X is also considerably slimmer at 6.9mm. Combined with a metal frame, glass back and a slight curve in the glass front at its edges, the X is attractive and feels great to hold.

The device is available in two colours, Onyx and Ceramic. The latter is priced considerably higher at Rs. 22,999 and is expected to be a limited edition, although no availability details have been announced for India yet. Realistically, you're limited to the Onyx variant, which is just a fancy word for black. The metal frame of the device is grey, with a striped texture that further contributes to the attractive look of the OnePlus X.

The back of the OnePlus X is glass, and is surprisingly sturdy and resistant to damage. OnePlus has not specified if it is reinforced. The black material under the glass makes the back highly reflective, a look we rather like. The top-left corner has the camera and flash, while the OnePlus logo sits just inside the top-third. This minimalist look goes well with the reflective back.

The frame of the OnePlus X is metal, with a lined pattern that continues all around the device. The top has the 3.5mm socket and a secondary microphone, the left has the notifications slider, the bottom has the speaker grille and USB port, while the right side has the power and volume keys and the SIM tray. There are two visible grilles at the bottom, but only the one on the left actually houses a speaker. The right grille is designed that way only for design symmetry.

It's important to note that we had some issues with the power and volume keys within the first couple of hours of unpacking our review unit. The power key was bent out of position for no apparent reason, and forced the device to go into a reboot loop. While we were able to fix this quickly and the power key remained functional, it stayed bent for the remainder of our time with the phone. Additionally, on one occasion, the volume rocker also popped out of place till we pushed it back in. We aren't certain if these build issues could affect all stocks of this phone, or are specific to our review sample, but it's certainly something to be aware of if you plan to buy the OnePlus X.

The notifications slider is another feature we found interesting. This is a three-position switch which lets you choose how many notifications you wish to receive. The lowest position will allow all notifications through, the middle position will only enable priority notifications, while the top position blocks everything. While some users might like this functionality, we didn't really find it useful. The switch could have been used to control ringer profiles, such as loud, vibrate and mute, which would have been much more appealing. Unfortunately, the switch's functions are not customisable, so it's something we ignored during our time with the device.

The OnePlus X has a 5-inch full-HD Amoled screen which we absolutely loved. It's incredibly sharp, detailed and vibrant, as is to be expected. It's comfortable on the eyes and easy to view even from odd angles and under sunlight. Furthermore, the phone takes advantage of the Amoled technology to enable a low power 'duochrome' mode, which wakes the phone to show you the time and any notifications without lighting up the entire screen. This uses the proximity sensor and doesn't always work well. Also important to mention is the fact that the soft keys at the front are not backlit, but can be deactivated and replaced with on-screen soft keys through the Settings app.

The OnePlus X comes with a factory-fitted screen protector film. This could be a welcome addition, since many people will want to apply a screen protector anyway. Unfortunately, the protector doesn't cover the entire front of the device, leaving the curved edges exposed. This also takes away some of the tactile appeal of the curve. However, to most users, some protection is better than none.

Specifications and software
The OnePlus X runs on a 2.3GHz quad-core Qualcomm Snapdragon 801 SoC with an integrated Adreno 330 GPU. This chip was used in many of the popular flagship smartphones of 2014. Although it's not the most modern now, it's still a capable SoC that offers excellent performance and outdoes this year's Snapdragon 615 in most benchmarks. Although the use of a previous-generation processor on a late-2015 smartphone might come off as questionable, we were more than satisfied with the performance of the OnePlus X for its price.

Apart from the SoC, the OnePlus X also has 16GB of internal storage, dual-SIM connectivity, 3GB of RAM, and a non-removable 2525mAh battery. The SIM tray has slots for two nano-SIM cards which both support 4G connectivity, but the second slot is hybrid and will force you to choose between expandable storage (up to 128GB) and a second SIM. Charging and data transfers are done through a standard Micro-USB port, but this phone unfortunately does not support fast charging. NFC and wireless charging are not supported either.

While the OnePlus One initially came with Cyanogen OS, later versions switched to the company's own Oxygen OS. The OnePlus 2 and X have stuck to the new operating system, and version 2 of Oxygen OS is preinstalled. On powering up the device and connecting to the Internet, an update to Oxygen version 2.1.2 was immediately available for the OnePlus X. The current version is based on Android 5.1.1.

Oxygen OS itself is very similar to stock Android Lollipop in terms of look and feel, especially in the app drawer and notification and quick settings bar. There are a few additions on top of stock Android's typical features, such as a detailed app permissions screen which lets you tweak the permissions granted to specific apps, a 'dark mode' that changes the general look of the interface to darker colours, customisable colours for the notification light, and custom screen control gestures, among others. UI performance, too, is in line with what we're used to on stock Android.

The 'buttons' menu is something that Oxygen OS has taken inspiration from Cyanogen OS on, and adds some interesting customisation options. The non-backlit Android soft keys were quite bothersome, lacked proper markings and were hard to use, so we were quick to deactivate them and replace them with an on-screen navigation bar. Additionally, the Back and Recents buttons can have their positions swapped, based on your personal preferences. You can also choose to leave the off-screen home button active even when using on-screen keys. If you choose to use the capacitive keys, you can set up additional long-press and double-tap commands.

The Shelf feature, which can be accessed by swiping left from the primary home screen, is simply a weather forecast and list of frequently used apps and contacts. On the whole, it's a decent custom user interface that retains the best of stock Android but still adds enough to keep the system interesting and useful to users who want more control over their devices.

Camera
The OnePlus X has a 13-megapixel f/2.2 primary camera with single-tone flash, along with an 8-megapixel f/2.4 front camera. Both are capable of recording up to 1080p video in normal mode. The rear camera can additionally record slow-motion video at 120fps, but only at a resolution of 720p.

The camera app is designed to look like Google Camera, but has a few differences. There are buttons for quickly toggling the flash, self-timer and camera switcher, but accessing beauty, HDR and clear image mode is a two-step process. Video, panorama, time lapse and slow-motion modes also require some swiping to get to. Although Oxygen 2.1 brings a manual mode to the OnePlus 2, manual settings remain absent on the OnePlus X even after the update. You can, however, easily set the photo and video resolution.

The camera itself is quick to shoot, and is excellent in terms of colour and lighting reproduction. Shadows and sunlight interweave splendidly in outdoor shots, while indoor pictures bring out the best in both well-lit and low-light conditions. Unfortunately, that's where our praise for the camera ends. Looking at our sample shots closely, we found a glaring lack of detail in every shot we took.

Noise and grain are plentiful without even zooming in all the way, and it's impossible to distinctly make out any detail in pictures of subjects that are more than a few feet away. Even in close-ups, anything outside the focus area is utterly lacking in definition and clarity. The front camera has the same issues, and is as such only somewhat usable outdoors. Indoor shots are far too grainy and noisy to be considered any good.

Performance
Thanks to the capable Snapdragon 801 SoC under the hood and the efficient operating system and interface, the OnePlus X is a decent performer. It's helped along by the 3GB of RAM, and moving around the interface and through most apps is snappy. The device ran our test videos well, including the heavily encoded files, and ran our usual test games comfortably too. There were slight heating issues when playing Angry Birds 2 and Dead Trigger 2, which also caused some heavy battery drain.

The OnePlus X performed capably in most of our benchmark tests. It scored 24fps in GFXBench and maxed out in 3DMark Ice Storm Extreme, producing a score of 16,207 in Ice Storm Unlimited. AnTuTu returned a score of 40,773, while Quadrant produced a score of 24,013. All of these scores are in line with a lot of 2014's flagship devices, and are excellent considering this phone's Rs. 16,999 price tag.

The phone does well in terms of call quality and holding on to Wi-Fi and mobile networks as well. Sound volume from the single speaker is a bit weak, but the device does produce good audio when you connect a pair of headphones.

The X ran for 11 hours, 54 minutes in our video loop test, which is excellent for a 2525mAh battery. However, we found that in practical situations, the battery wasn't quite as capable. As previously stated, gaming and other intensive tasks would cause serious battery drain. The device will only last a full day on a complete charge if used carefully and conservatively. While calls and texting don't affect the battery too much, Web browsing and gaming tend to eat away at it much more than we've seen on other similarly specced devices.

Verdict
OnePlus has made serious waves in the smartphone industry since its rather dramatic arrival on the scene less than a year ago. It's offered products that have matched flagship specifications at prices that are much lower. Questions have been raised over the company's products from time to time, and the invite-only system for purchasing OnePlus phones, at least while they're still new, continues to annoy potential buyers. However, despite all of this, they can still capture everyone's attention.

Where does the OnePlus X stand in all of this? It's a decent mid-budget device that offers strong performance using a dated but powerful SoC and more than enough RAM. It also boasts of great looks, a premium feel, good software, and a superb screen. However, the quality of the build is somewhat questionable, and the camera is utterly lacking in detail and definition. Heat dissipation issues have a tendency to negatively affect battery life. If you do choose to go for the OnePlus X and manage to get your hands on an invite, this is a decently rounded phone which offers a good combination of performance, looks and software.