It's a distillation of all the tactical depth in nu-XCom, but without any of the RNG or weird abstract line-of-sight rules or other infuriating abstraction.
It takes place in procedurally generated 2d sidescrolling levels that your troops navigate with 2 action points, and they automatically crouch behind cover. The twist is when firing your gun there's no dice roll, instead you aim the gun manually like in Bust-a-Move plus some built-in wobble.
This makes all the difference in the world. You can tell at a glance visually whether crouching behind that overturned oil can will provide you any cover from the sniper on the catwalk above. If you miss, it's because you screwed up your aim, not the RNG saying, "fuck you." They even have an entirely pointless but OCD-compulsive mechanic where near-miss attempted headshots knock the enemy's hat off their head, which you can pick up and wear.
Each of the characters as they level up are clearly based on each of the class archetypes from nuXCom. And the new game+ lets you start with all the characters you unlocked over the course of the campaign so you can start over at level 1 with whatever crazy class combination you desire.
Unless you're allergic to the concept of steampunk robot space cowboys, I can't think of a single flaw in this game.