I find the audio to be abysmal in-game, but in the menus it is fine because it's not a constant barrage of SMACK & CHING and nothing else. In that regard, please make the audio more dynamic. Music and stuff is fine but god damn, there's a reason I always have it muted.
If you can't find a way to make your energy regenerate while one is not connected, how about whenever you level up and assign statistic points, each "point" you put into the Energy attribute accumulates by at least 2? So 1 stat point = 2 energy points, or whatever you wish it to be. Because at the rate of energy use & the rate of energy increase, since so many people will level up their attack, HP, and defense attributes first, it's just not a plausible system.
Later into the game, like during the extra battles (especially the extremely hard levels, which I'm up against now), the game becomes a grind for points, which don't go a long way. I don't know why you'd make units less flexible in terms of their health and power than before, even considering the addition of equipment.
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