Thoroughly impressive...
Not much more to add that hasn't already been said. I will say to those who don't get what you have to do, here is a list of where the endings are:
*Credit is given to Petar4418 for the notes on page 10 of the reviews*
Portal Opening Guide:
1) Go through Starting Portal
2) Wait 1 min in Looming then go through Starting Portal
3) Go through ending Portal on other side of Looming
4) Triangle Building (Tally Beads)
5) Science Dome (Rings)
6) Dirt Piles (Bones)
7) Do the star puzzle #2 Star-Facing [NW-N] [NE-S] [SW-SE] [SE-NW]
8) Unearthing Messages (Must unearth all messages to see the portal)
9) Do the star puzzle #1 Star-Facing [NW-W] [NE-S] [SW-E] [SE-N]