Kristjan Korela designed and implemented for his thesis a pretty lengthy horror-adventure game Spookytown. The game world has fantastically designed architecture and characters. The game world is a mix of coziness and spookiness. Everything seems cute and welcoming until a giant pumpkin monster starts chasing you through an underground tunnel. In total there are several hours of gameplay here. The thesis describes, along with the inspiration, implementation, and playtesting, the environment and puzzle designs for the four chapters of Spookytown. So, to avoid spoilers you might want to play the game before reading the thesis itself.
Poster
Thesis