Changing gears from conceptual design to a physical prototype brings challenges that you might not initially think about. With a card game specifically, you're essentially creating the entire game before you can playtest anything. That means that you're going to have to spend a lot of time writing things out on cardstock, or spend time on a formatting program to work on printing out the cards.
Today, Mik and I spent more time than we anticipated just trying to get the physical prototype in order. Having done all the work and everything laid out in spreadsheets made this process easier, but didn't remove all the gruntwork that stood between us and our first playthrough.
Not surprisingly, we're both anxious to start. We're at the point in design where nearly every conversation ends with something along the lines of "well, we won't be able to tell which is better until we play test it", and being at that point is really exciting. So far, we have decks completed for vanilla ADC, Support, and Tank characters, even with roughly cohesive deck themes (Raymund the Electronaut, Temper the Boilerman, and the Gentleman, respectively). With the last few minutes of development today, we printed out a slightly unfinished version of the campaign one/game one villain deck, the Spiderlings.
Recently, we've also been surprised at how much effort creating a unified and cohesive villain has been. Making heroes was relatively easy because its everything that we've wanted in a co-operative deck building game. The villain, however, has proved particularly challenging because it's essentially the entire game. We can't make the villain too easy or the game won't be fun, but if we make it too hard the game won't be winnable, which is even less fun. On top of that balance, we have to give the players interesting choices to reward them for optimizing their hero's abilities, but not restrict them to such a narrow set of plays that they have no choice in what to play. It's quite the line we have to walk.
For now, we're just anxious to start playtesting. We both expect a large amount of rule-changes after playing, and we're hoping that those rule changes won't have to include axing some of our favorite aspects of the game.
-Jake