It took some thinking, but I’ve come up with an idea.

It’ll be a platform game where you play as a pair of cavers who need to get out of a cavern. Unfortunately, neither of them can see all the platforms (although both of them can stand on them). The idea is to move both of the cavers upwards so that you can use the vision of one to ‘fill in the blanks’ of the other. As I’m using the DS I’ll use each screen to display the vision of one of the cavers.

Not sure how well this’ll turn out, but here goes…