Personally I think it's a really neat minigame. For the most part, it's pretty simple although there's also the element of making your coins as valuable as possible, and getting items or GGs on the side.

They did a pretty bad job balancing the echos though.

Coin Count Echos are rather well-made for the most part. They give more quota the more coins you use but the more coins you use, the less you will have available later on. Interesting balance, but they suffer from one huge problem, and that is that a 1 in the center breaks your echo without you being able to do ANYTHING about that. When I challenged Varan, the 1s became my mortal enemy. 500 quota in just 30 turns, if there's a few 1s spread out too well you can just give up right there.

Multiplier Echos on the other hand are ridiculously good. They completely trivialize all challenge Sphere Break might've had. You can always make sure your chain never breaks, and as long as it doesn't, it will rise to absurd values to the point where you can get immense quota with just one core break. 600 quota in 30 turns? Easy, I finished with 750 in just 25 turns.