Go Write!

"Characters acting on the situation," that's a good way of putting it. And probably one reason I'm finding the experience helpful - I think it's more difficult for me to plot for acting in addition to reacting. My game has become more character-focused as we've developed them, but that process has also been unusual for me in the extent to which my development of the character has been prompted by plot events, rather than the other way around. And unusual tends to lead to good things in writing.