system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] Does a werewolf transform automatically on nights of the full moon, or do they physically have to have moonlight touch them to transform?

In the book and movie, Lupin doesn’t transform until they are outside and the moonlight hits him. This implies he doesn’t transform until contact is physically made. Doesn’t this mean if someone doesn’t want to transform, they could just build a windowless room in their house, like a basement? Or if they have no recourse but to transform on nights that where full moons occur, why doesn’t Lupin transform when nightfalls while they’re still in the shrieking shack?
gpt
From what we see of Lupin, it might be a matter of observing the moon, seeing as he did not transform until he gazed upon it. Or at least, seeing the moon accelerates the process.

Otherwise, the Shrieking Shack would not exist, seeing as Lupin could just hole himself up in a sealed-off room for the night, and have a clock to tell the time. (Unless he wasn't aware of that aspect, being effectively a primary/high school student). Thinking about it, that might be part of why he is absent at certain times of the month, since he seals himself in a windowless room, and avoids interaction, just in case.