From the trailers before the game released, I assumed Ball x Pit would be good. I didn't realize it would be among my favorite games of the year. This was nearly impossible to put down for me. The core loop seems pretty banal at first - drop your character into a scrolling, walled pit armed with damage-dealing balls against a never-ending cascade of enemies, capped off with a boss fight at the end.
When the "offer 4, pick 1" mechanic pops on level up, you get to see some of the special balls. Then you get your first evolved ball - and you realize there is much more than you're being presented with up front. Then you start unlocking some of the new characters and the possibilities seem dizzying. Some of the character abilities made me laugh out loud when I unlocked them.
My only real critique of the game comes from the town building minigame, which is fine but certainly not as strong as the core game. I enjoyed it more when trying to min/max my layout, which I am sure is the developer's intent.
It's rare for me to want to chase high scores and achievement hunt, but that's exactly what I did in Ball x Pit. Even having 100%'ed the game, this will remain installed on every device I own, and I surely will return to it on occasion.