INSIDE

Early flooded-room area (around checkpoint 15). After you make a hole in the floor, drop down and interact with the vent on the LEFT to enter a small hidden room with the orb.

Yellow-submarine / mind-control section (around checkpoint 30). Instead of going through the red door, head down; move a block to reveal a hidden tunnel near the mind-control-helmet area and reach the orb below.

Underground-city / decrepit-sign area (around checkpoint 16). Slide down the slanted roof, jump to the pipe and slide DOWN instead of up; take the ladder on the left down into the alley to the orb.

Hanging-bodies / testing-facility box room (around checkpoint 50). Carry the yellow box up and use it to push the red button that raises a secret platform; ride it up to the orb inside the large sphere.

Yellow-submarine / mind-control section (around checkpoint 30). Instead of going through the red door, head down; move a block to reveal a hidden tunnel near the mind-control-helmet area and reach the orb below. (This is a duplicate row of the other "Friends in Low Places" - one orb resolves both.)

Underground cave near the mind-control helmet (around checkpoint 34). Find the yellow cable, use your drone followers to pull the plank blocking the shaft, then descend the ladder into the cave to the orb.

First underwater-lake escape (around checkpoint 6). Dive and swim LEFT along the underwater cave into a room with a pillar; rock the pillar back and forth to bridge across to the orb - the earliest one.

Cornfield bunker (around checkpoint 7). In the crops, spam interact to find a hidden hatch; descend the ladder and head left toward the red light to the orb. (This is the same bunker used for the secret ending.)

Deep underwater past the rotor tunnel (around checkpoint 47). Dive down, open the large door in the left wall with the two red handles, then swim through the tunnel to the orb.

Basement office / elevator area (around checkpoint 54). Reach the basement elevator with your followers, then split them into two groups (one upper, one in the office) to work the elevator and reach the ceiling orb via the yellow rope.

Beach / shoreline in the submarine (around checkpoint 32). Steer the sub LEFT back toward the beach and ram the ladder-structure twice to destroy it, then climb up to the orb.

Pig barn (around checkpoint 9). After the jump, push the cart of dead pigs LEFT instead of right, climb on it, pull the plank from the barn side and use the revealed room / rope to reach the orb.

Water-girl chase (around checkpoint 44). Open the latch on the far right to draw the creature there (push the red button to send it right), then run left, dive and swim left into the secret area with the orb.

Rotating-platform / shadow puzzle (around checkpoint 48). Turn the wheel so the mechanism's shadow is directly overhead ("noon"), which opens a steel door; dive down and left and climb the middle ledge to the orb.

The alternate secret ending. Destroy all 13 orbs; the final one kills every light except the cornfield-bunker light - return to that bunker (the Field Research spot), enter the vault code (Up, Up, Right, Left, Right, Right, Right, Up, Up, Up, Right, Left, Left, Left), then in the final crawl space climb UP into the giant-orb chamber and interact to trigger the ending.