VN Screen sizing

[Geckos]

So I've been wandering around the forums for a few days now. I'm extremely excited to have found a place that's all about visual novels!
I am working on my own at the moment, and I will likely upload a WIP forum of the game once it has a more solid form.

My question is:
How hard is it to create a game that can be a max of 1920 x 1080 res at full screen, but also be able to have a smaller res version for those who want to play in windowed mode? I notice that a lot of games just stick with a set resolution that is basically a square that takes up 2/3 of your computer screen. Any sort of info on this topic would be appreciated!

[KomiTsuku]

Somebody correct me if I am wrong, but I think the newer versions of Ren'py allows you to dynamically resize the screen in window mode on the user's end.