Feels like an idle game since paddling provides too little to actually bother paddling. I think this is also a problem with the difficulty curve - early levels don't need you to regen mana for the balls, while in later levels it won't matter since your ball will die before reaching the paddle back.
Shop is nice, I dig different ball ideas, though not all balls are made equal I guess - heal ball is kinda trash before the first merge, while earth ball is good from the get go. Predator ball is fine, fire ball needs item upgrades before it becomes viable - and even then it's still very reliant on RNG.
Music is nice, I like it quite a lot.
Good stuff, but needs more tweaking and polish.
Also - you can just not release the balls when the level starts and win every single round. Probably a bug.