1- in the area with glowing platforms
1-when you get to a room with a huge light cross on the wall in front of you, its on the right
2-after going through the first "black floor"(its the floor that kills you when you fall into it) its in the right corner of the room
3- In the big room with lots of pillars, on the left up high
4-In the room where you have to perform a leap of faith, it's above the big assassin symbol, just under the roof.
1-Big room with the block-blocking areas, up high
2-After the room where red walls almost crush you, you'll have to use the jump block to jump through the gap. Instead, use 2 triangle blocks to get higher, and then use the jump block to get to the item located up high on a walkway above you
3-Right after number 2. Use 2 triangle blocks to get higher, then use the jump block to get to the collectible located up high across the gap
1- After the 5th forcefield(?) it's up high on a catwalk.
2-After the big room with lots of memories on walls, you'll come to a room with lasers. Immediately after entering that room, turn left and look above you. The collectible is floating in the air.
3-Right after you go through the first yellow lasers is this memory, it's on the left up high.
4-After dropping down through the hole you made by pressing a button, you'll find yourself in a room with an image of a firefighter on the right wall. In front of you is a passage. Go through it, and the collectible will be on the right, above you.
1-When you get to the deadly black floor again, you'll be able left & right, the way to the left is blocked by a forcefield, so go to the right.Don't go up, instead turn around and you'll see the collectible in front of you.
2-After having a flashback of a portal, you'll enter the room with a hole & lasers in the floor.Go straight and to the right. The collectible is located behind the pillar.
3-After dropping down the hole, its on the opposite end of the room from the button.
4-After the hole with yellow lasers, you'll need to press a button guarded by more yellow lasers. The collectible is directly above the button.
1- On the river of Styx. Instead of following the path to the left, go right and get the collectible from a platform.
2-When you get to the "park" section with trees, it's up high on the right wall.
3-After going up a shaft with flying black blocks, it's floating in mid-air above the black floor.
4-Soon after the previous one, after going up a shaft with red lasers. When you get to solid ground, it will be on a ledge above you.