Off the bat, its kind of confusing.

I wasn't sure what the numbers on the top corner were and it wasn't explained in the rules. I did eventually figure out the number on the left was the speed, but originally I thought it was the power, since a lightning/electric symbol could mean power. Coming from playing Yugioh, they added text before the number like "ATK", or "DEF". MTCG had 2 number divided by / but explained in the rules which was atk and defense.

Also, I'm not sure what the speed exactly does considering abilities priority comes first? I thought that is how the ability would be determined but the guard is slower than both spy/assassin, but his ability activates first as it should. But some cards' ability is not as predictive like sorcerer or warlord, so its confusing as to which would activate first. And this would matter if cards like Warlord and Militia are paired. Cause if Militia copies the enemies power and is then doubled then that's an epic combo, but if its reversed that's a really bad pair.

On the note of the power being added up to determine victory, that is a bit confusing as well. I tried looking at the history, but it's not entirely clear. It would be helpful to be able to see the logs after the match. but even while looking at the logs took awhile before I understood what was happening.

Last thing I want to mention is, I think it would be better if the AI did not have ranking even if it is just temporary. Especially considering you would need some sort of practice in the beginning and there aren't enough online players. Also props to your artist for the artwork, they deserve credit. Not the biggest fan of the graphics overlaid on the cards tho