kingdom hearts 1.5 and 2.5

I loved the original kingdom hearts that came out when I was a kid, so knowing it was about to have a new game I wanted to get it again. I just bought it and now I can't help but wonder if I should take it back. I don't understand card based game play... why did they change the format so drastically. I'm going to give it a try but I feel like I just bout a game for 27$ and will have to return it tomorrow and only get 3$ for it....anxiety sucks. I hope I like it as much as I used to...