Besides being a grab at people's desire for more Kingdom Hearts, KHXU isn't much in terms of a game. It's full of free to play mechanics that I dislike - mainly fusing stuff and getting random items in exchange for the premium currency - but I've gotta say that the kingdom hearts feel is there. With some retooling this could've been a 'real' game that I would've cared about as an entry in the KH franchise, but besides being a grab for fan attention, it's a bit disappointing.
After booting the game for the first time you are treated to a download process that takes forever. I get it, you make your apps smaller and you download the extra content - I know this is not only KHXU's problem - but that was kinda dumb. Then you create your character's appearance - no choice between three items in this game - and select an 'union', a loosely affiliated group of players that work 'together' towards... something? Objectives? I'm not sure. I also dislike how the game kicks you back to the home screen if you play it on a different day, I know it's because they want you to go through daily bonuses and stuff like that, but it's annoying. There's an energy timer gating how much you can theoretically play, but I never had a problem with it - because I never played enough in one sitting for it to be an issue.
You move around by tapping on the screen and your character walks that way, you get materials and other items from chests laying around maps, alongside munny, hp and special attack orbs. You initiate combat by bumping into an enemy, battles work like this: You have a few medals socketted in your keyblade and you can use them by tapping on a single enemy for a single-target attack, swiping the screen to attack all enemies or by dragging the medal for a special attack, if you have enough special meter to do so. After you've used all of your medals - plus one you select at the beginning of each map based on your 'friends', or whoever they are - enemies get a turn. Defeating enemies in one turn give you bonuses and most maps have an optional quest that asks you to defeat them all in one turn.
There's plenty wrong with the battle system and that breaks most of the game for me. It's quite impossible to gauge properly how strong enemies are and if you're going to be able to defeat them, even the rarest medals I got from spending premium currency didn't seem to be doing more damage than my cheap ones - even when fully leveled. There's a rock-paper-scissor system that is discouraged by your keyblades boosting certain type of medals - so you'll more-or-less always have something weak against an enemy - and they can kill you very quickly. Many bosses or optional enemies I've faced would kill me in two rounds and even if you do get HP orbs from hitting them, the recovery is mediocre.
There's plenty more stuff to talk about for KHXU; You can level-up your keyblades using materials found on maps and gained from quests; You can level medals by fusing other medals into them, then evolve them using rare medals; There are a bunch of 'avatar boards' where you spend avatar tokens to power up your character and buy a bunch of useless cosmetic gear along the way. There are raids where you're supposed to team up with friends to defeat a huge boss but you'll mostly die and defeat them in a weakened state on the second try. KHXU is a weird thing, it's trying to be a 'real' KH game but at the same time it plays nothing like one and the story didn't seem that important either. If you're a die-hard KH fan like myself you might want to give this a shot, but otherwise there's not much of value here.