How to detect when laptop power cable has been disconnected?

Question

For the umpteenth time my laptop just shut down in the middle of my game because my power cable had disconnected without me noticing it.

Now I want to write a little

Answer 1

To continue BQ's answer, there are power settings in Windows that can be changed when the power cord is removed. Since I sometimes work with it removed I didn't change the power settings on my machine, but when the battery approaches 15% the screen brightness is set to the lowest level, making it possible to work (and easily changeable with Fn-Home key) but very noticeable so that I plug the cable back in time.