Ok, here's the general idea of what I want to do.

After a certain time, I would like the computer to nag me to go to sleep. Maybe every five minutes or so. But I don't want the messages to pop up if the screen is locked, because I leave it like that all night.

Ideally I would like to be able to do more things like shut down running instances the web browser, or lock my user session if I ignore the notices for too long. But I'm happy with just popup messages if that's all I can do.

So, how much of this is possible and where do I start? I'm not too well versed with task scheduler, and I'm assuming I'll use that to at least start whatever script I have to put together.