What happens if both players have grav shifts? How would that play out?

Easily.

First Player places his Token before the second Player places his token.

Then, when its time to move the Obstacles...

First Player Move the Obstacles that he can, before the Second Player Does... Which, of course, may invalidate the Second Players placement of the Grav Shift Token.




RRG, page 5, "Effect Use and Timing:


• If both players have effects with the same timing, the first player resolves all of his effects with that timing first.

Perfect. Thanks.