Here is the full list of all 29 GYLT achievements.
Escape from the Arcade without being detected by Exposure
Shock an Enemy
Use the Planks to Remain Dry
Escape with Both Sally and Emily
Get all the Diaries
Freeze one Enemy of Each Type
Free all the Inhabitants
Try to Play other of Tequilaworks Game
Defeat an Enemy with the Flashlight Beam
Escape with Emily
End the Game without Killing Anyone (without bosses)
Escape with Sally
Escape from Helplessness
Reach the Final Mine
Defeat Violence
Hoop a can
Reach the Basketball Court
Freeze an Enemy and Push Him
Access the Art Building
Defeat Exposure
Kill an enemy with a Stealth Attack
Get into the Theater
Defeat Violence in the Laboratory Without Being Hit
Blind Three Enemies at the Same Time
See the weirdness in the school
Remove the battery from the Arcade core
Get outside of the school courtyard
Hit an enemy with a can
Enter the school looking for Emily