At the time, their website was only in Swedish and Danish so I found a travel agent in Minnesota to book it for me the first time I crossed. I crossed a few years later with some friends and we just booked it when we got there. There are several small amusement parks in northwestern Denmark and a really good one (Liesberg) in Goteborg, Sweden. That's why I've been there a couple of times.

I do remember that both allowed cars. The first time I went I didn't have a car in Goteborg, but got one in Frederikshavn. The 2nd time we started in Brussels and we had the car for 3 weeks, so we left our luggage in the car in our car on both ferries.