The User Interface, or UI, is the mainstream appearance of the game engine.
The Old UIEdit
Combat Arms' first and original UI was a uniquely camouflaged browser that gave the game a very humbling atmosphere. Each part of the design was made to look very military-esque, and the encouraging BGM was an army march that made players feel excited. The Old UI focused heavily on imagery rather than words, and it was simple and easy to use. The Shop and Black Market used a basic format, with different tabs for each item category. Though it was slightly less organized and harder to navigate than the current one, the Old format allowed shopping to be exceedingly simple. The large images and clickable icons allowed players to easily view what they were purchasing before they bought it, and the pop-up statistics allowed for quick and easy weapon comparison. The clan page was built in a similar way, making it no less harder to navigate. The log-in, pre-server, channel, lobby, and game room formats were elegantly designed to be simple and effective.
The New UIEdit
Combat Arms' second and current UI is a "sleek", metallic interface that is supposed to make the game seem more high-tech and easier to use. The design is a dark grey, steel format that resembles a modern machine. The BGM was also changed to fit the new UI, featuring a new, more "exciting" tune. The New UI focuses heavily on words rather than images, making it very hard for a new user to navigate. The Shop and Black Market retain several details of the old format, including the re-implementation of the old dressing room and other weapon images. However, since these aspects were re-used, they do not fit well with the new format, often appearing glitchy and pixellated. The new Shops are designed to be much more organized and useful for shopping. Though it does make things more organized, it also makes it much harder to find things. Players must scroll through long lists of names (without pictures), click multiple tabs, and manually find what they're looking for. Clicking on an item allows the picture, statistics, and item description to appear, though it is small and unclear. Much of the text is "crammed" together, so some users have trouble finding stuff. In addition, the search browser in the top right is usually no more than a decorative item, since many items that are searched do not even exist in the Shop and Black Market, but instead belong in the MYST-N and Hi-Sec Cases. The Clan page follows a similar pattern, with the same square frame and functions. In addition, the Clan Shop also appears on the clan page. Though the log-in screen remains the same, the pre-server, channel, lobby, and game room formats are much different from before. The metallic design can sometimes seem "cheap", or "plastic." There are multiple buttons for multiple uses, such as the Options, the Start button, chat room, messenger, and advertisements, which can be overwhelming to the average player.
The New UI was heavily criticized on its initial release. Many players wanted the Old UI to be re-implemented in the game, and petitions and groups formed almost instanly, to no avail. With no response, Nexon refused to revert back to the old design, and instead chose to "compromise", by slightly editing the New UI to its current state. Still under critical scorn, players eventually calmed down and got over the new changes, partly since they were powerless to do anything. Nonetheless, players did and still continue to protest the changes, and many people have suggested that an engine repack should allow transition between the Old UI/BGM and the New UI/BGM.