Idle Shadows is your typical idle game with some flaws. The game plays in vertical mode which I already hate. The main problem with the UI is that everything is just crammed onto the main battle menu. When you want to upgrade your characters skills or anything you just click on the tab and a very small section opens up under the battle screen. You need to scroll to see all the different stats and determine which you want to upgrade. I would rather see this added as a full screen experience to see everything better. The menus need some serious work.
It does have a button on the right that can expand it slightly, but it really doesn't help much. The audio was decent but nothing amazing. It at least has some background music. The game has lots of different ways to spend money to speed up progress. The game also lets you watch ads to get time limited buffs to your character. This is all pretty typical when it comes to these idle games. Many features are locked at the beginning, and you will see a lock icon over it. This is a nice feature so new players don't get overwhelmed with content. However, there is no indication of when you can unlock these features.
Overall, it's a decent idle game but I have seen better. If you like the vertical aspect, then it is worth a try. Otherwise, I would say find another idle game because better ones are out there. I would give this a score of 5/10 I think it's about an average game at best.