Here is the full list of all 43 TRI: Of Friendship and Madness achievements.
Play through the tutorial mission.
Play through the first four Chapters.
Play through Chapter 5 to 8.
Play through Chapter 9 to 11.
Play through Chapter 12 and 13.
Play through Chapter 14 and 15.
Complete TRI.
Create 1,000 triangles.
Find all hidden idols in one level.
Find all hidden idols in three levels.
Find all hidden idols in seven levels.
Find all hidden idols in 14 levels.
Laser yourself to death ten times.
Fall into deadly acid pits ten times.
Reflected one single light ray 50 times.
Beat "Overcoming Limitations" without collecting the TRI artifact.
Create the biggest triangle possible.
Find one of the two super secret idols in "The Odd Gods' Entrance".
Find one of the two super secret idols in "Tower of Nowhere".
Find one of the two super secret idols in "Three Sides to Everything".
Find one of the three super secret idols in "Overcoming Limitations".
Find one of the two super secret idols in "The Foxes' Playground".
Find one of the two super secret idols in "Unwilling Walls".
Find the super secret idol in "Wings in the Void".
Find one of the two super secret idols in "Glimpse of Light".
Find one of the two super secret idols in "Interrupting and Bending".
Find one of the two super secret idols in "Red Means Dangerous".
Find the super secret idol in "Out of the Box".
Find the super secret idol in "Going Astray".
Find one of the two super secret idols in "Prisons".
Find one of the two super secret idols in "Out of Space and Time".