How can I tell if I've frotzed my mini-laptop?

I have a little 10” Asus, 3 years old, that I’ve been using regularly away from my desk. Two nights ago I plugged it in to charge while it was in sleep mode rather than shut off. Last night I couldn’t get it to come on at all, not even to display battery level.

What can I look for or how can I tell if I’ve done something terminal?

I wouldn’t have thought there was any harm in having it charging while technically not shut down, but that’s the only thing I did out of the ordinary.

Advice?