The mobile* version of Gems of War could benefit from several improvements, mostly with the user interface.
The most needed improvement, is letting devices use their own sleep and wake routines while Gems of War is active. Currently, a device is prevented from entering a sleep state while Gems of War is active. This leads to greatly increased battery consumption if you forget to switch out of the game before putting your phone away. It’s more annoying aspect (to me, at least), is that I’m used to waking my device with the fingerprint scanner as I pull it out, and that doesn’t happen with GoW. I have to swipe across the screen to see what’s going on. This app behavior would have been virtually unnoticable a few years ago, but it’s very intrusive on modern devices. There’s also the security aspect of a device staying unlocked when you expect it to lock itself shortly after you put it away (in your purse/pocket, on a belt clip, or whatever). This gameplay lends itself very well to short bursts, so the app needs to support quick and unintrusive sleep/wake operations.
Less important are the various UI behaviors and designs that are poorly suited to modern mobile devices. There are a lot of unnecessary prompts and animations that require tapping a button in the corner to skip past (e.g. chest opening animations, the daily news screens, etc.). Unlike a PC or console this isn’t as simple as tapping escape or hitting start: you have to first spot the relevant control on a cluttered screen then reach over with your one screen-touching finger.
Another UI design issue arises from the prevalence of curved screens in the market. These make tapping controls along the upper and lower edges of the screen (when in landscape mode) slightly trickier so any control likely to need a short flick should be located a certain distance in from the edge.
GoW is a lot of fun for a freemium game. There aren’t many games that have lasted so long in a very competitive market. It just needs a few minor tweaks to keep up with how the industry has changed in that time.