The game balance for adventure mode is... odd. In some of the earlier chapters you can beat gold while getting ROFLstomped by bronze later on. The difficulty jumps up quickly in some chapters without warning.

The 12 hour cooldown on the arena chest means you are probably not going to be able to do it twice a day. An 11 and a half hour cooldown would at least let you attempt to get in 3 wins in the remaining half an hour.

In the Research lab, you don't get a preview of what will be created, you have to go back and forth between the combo screens. It would be nice if there was a preview before you start the research.

I have run into several issues in battle:
Sometime a card is destroyed by survives at 0HP, and then I am forced to reload, and the battle isn't continued, it is just counted as an automatic loss.
Sometimes in battle, especially with multitouch on a touch screen, a card somehow magically gets a copy stuck in the display. This continues on during each fight until reload (as in, the card even shows up in new fights), though the card isn't interactable, it's at the top layer blocking the view.

Almost all, if not all, of the high end characters are Futas, while this is comedic, I would not be surprised if some people quit the game after seeing it.

When you finally fully defeat someone in adventure mode, there is a % chance when beating them that you will get viagra. For example, the first Polly has a 50% chance. (Not sure if this is consistent as I am F2P and she's the only one I've fully cleared) I have experience far, far less than 50%. 4/17 wins so far has rewarded Viagra, I'd ask them to look at this.

At least early game, cards being recycled into energy is comically bad, as you get to several points where you cannot beat any of the adventure mode fights. With the fights eventually capping out and still being able to be fought, this might balance out eventually.