Implementing a save feature scares me

[MediocreMetastasis]

This isn't a cry for help. I wanted to talk about how scary save features are. You can't just pause the game until the user wants to play the game again (Well I guess you can under extreme circumstances) so you have to find a way to save the current state to the hard drive. How do you do that? Save everything as a variable and write it to a text file.

For example, Half life 2 lets you save the game anywhere. Which means it needs to make the player's,enemies',all physic objects', projectile's position, rotation, velocity, torque, and ai state as well as ammo, current sound playing and it's current playback position all as variables just to write it to a text file.