Oppo R1x runs on Android 4.4 KitKat, made unrecognizable by Oppo's proprietary Color OS v2.0.1. The Oppo's launcher customizations run very deep, they keep all Google apps and services, and even bring quite a few of its own - themes support, new lockscreen, homescreen, and settings menu among others.
For the traditionalists among you, there is a preinstalled theme called Jelly Bean, which replicates the stock Android Jelly Bean UI for you as close as possible.
The Color OS default lockscreen uses swipe gesture for unlocking, though it only works with an upward swipe. You can set up pattern, PIN or password unlock protection. There are shortcuts for the Phone and Messaging apps.
The lockscreen also has a handy hidden flashlight shortcut - with the screen awake, a press and hold of the Home button turns on the LED flash on the back of the device and stays on for as long as you hold the Home button.
As is customary with Chinese manufacturers the Oppo R1x doesn't have an app drawer, so all of your app shortcuts are available on the homescreen, and the apps above the dock are organized in a grid of 4x5. Naturally, you can group your apps in folders the way you like, and widgets are available as well.
Exclusive space is Oppo's custom homescreen page. Currently, there are two available - Photo and Music. Photo space takes up a whole homescreen and features a small live viewfinder so you can take shots straight from your homescreen plus a shortcut to the full camera app. Below you get a timeline with all your recent photos and you can share them very easily.
The second Exclusive space homescreen pane is Music. It features a cool, if slightly unintuitive design with a vinyl for changing the currently playing song and stopping/resuming playback. You can change songs, go directly to the music player or the Phone app.
The homescreen's contextual menu lists widgets, wallpapers, effects and themes. You drag widgets upwards to place them on the homescreen.
Oppo's Color OS supports themes, one of which changes the appearance and functionality of Color OS to match that of stock Android 4.3 Jelly Bean. There are plenty of themes available for free in the Oppo's Theme Store.
By default the notification area will show one row of quick toggles, a brightness slider and a shortcut for enabling auto brightness mode, the current notifications plus a shortcut to go into settings. If you do a drag gesture from the quick toggles row you get two more lines of toggles. There's also a Kill all apps button there.
A long press on a toggle will bring up its respective settings entry. By the way, you can access the notification area even if you slide down from any empty part of the homescreen (not just the top), which helps single-handed use a lot.
The task switcher is pretty close to the one in iOS. All your apps are shown in a horizontally-scrollable grid of thumbnails, which you either swipe up to close or tap to open. A Kill all button sits central on the bottom.
Finally, the Gesture & motion menu deserves our attention. For one you can swipe with three fingers across the screen to capture a screenshot or pinch with several fingers to launch the camera and more.
The Motion options are very useful, too - flipping the device will mute the ringer, raising the ringing Oppo R1x to your ear will automatically answer the call and more. The Motion menu also offers Air Gestures on the homescreen - you can swipe through the panes with waving your hand over the display.
One hand mode is available too, activated by an upward swipe from the bottom left or right corner. When done, this will minimize the UI into a more compact window, possible to use and operate with just one hand. It's a lot like Samsung's feature in the Note series, though without the option for resizing.