Here is the full list of all 15 Looking Up I See Only A Ceiling achievements.
Unlock the Secret Ending.
Do only wrong actions during the breakfast mini-game three times in a row.
Find the authors of the game working in the Explore Mode.
Interact with ALL the points of interest in the Explore Mode.
Access the Explore Mode.
While looking for a way to enter the Bathroom, read all of your exams' notes.
Unlock both "Bad Ending" and "Good Ending".
Reach Checkpoint V-B.
Check the Bathroom’s shower before going up.
Talk 3 times to the man while he’s working before leaving his place.
Reach Checkpoint V-A.
Reach Checkpoint IV.
Reach Checkpoint III.
Reach Checkpoint II.
Reach Checkpoint I.