I’ve done some paper prototyping in the past but I forgot how fun it is. Recently I organized a tabletop game design competition and made a pretty sweet cooperative card game called Cryodream with Ryan Bujnowicz and Alex Ryan. The story is you are on a ship in cryogenic sleep heading towards a far away planet to colonize and every so many years one person wakes up to check if everything is operating fine. Before going back to cryogenic sleep you choose who will wake up next. Each member of the crew has a different job, for example, a mechanic can build and fix things while a diplomat is good at running away from hostiles. Over the course of the game you go through six different environments which have a special event (eg. a virus infection or being hit by asteroids) and probabilities of encountering hostiles, friendlies or nothing. If you acquire a second engine you can look at the next two environment cards and choose where to go as a branching mechanic.
It was quite hard to create and balance this game in about 8 hours and it ended up being too easy. The battle mechanics notably need work since there is rarely an instance where you’re in danger of dying. The environment mechanics worked quite well although I feel they could be expanded upon. One idea that we dropped during development was a grid based movement system inside the spaceship where proximity between generators and items that require power matters. I really liked this idea so perhaps it will make its way back into the game.
In short if you haven’t tried paper prototyping it is simply awesome. The developers of Shadow Complex discuss how they used it in a recent interview, which I highly recommend reading.