From the post:
In previous articles we’ve told you about the mechanics within the Shadowrun: Crossfire deck-building game. Things like how to defeat an enemy and how to help your teammates. This time, we’re taking it to the next level and talking about one feature that makes Crossfire really stand out. On the first day of working on this game I decided I wanted to make a cooperative deck-building game. It fit the 1-hour play experience we were aiming for, it would have the flexibility and variability of an RPG, and with players working together, it would feel like being on a small team fighting through the tough life of a runner. There was still one piece missing—a connection to your character between games. I wanted something to carry over with the player from one day to the next or to the next week. My solution was to add stickers (upgrades). Using an experience system, I thought I could add abilities to the players’ characters as a reward for playing several games, which makes the next game more enjoyable because you get a fun new toy to try out.