@jscottk, I just got this from my friend:
When he didn't turn on the Rift before running the game, he only got 1440x900 as the maximum resolution. So it looks like you have to make sure to turn on the Rift before clicking the game because you'll have no 1920x1080 option otherwise.
And also thanks! The green alien hand with mesmerizing moving bubbles is my favorite part of the app :)