Why won't my tablet open?

I had a friend over so I set my tablet to charge and left it for the rest of the day. That night, I saw it flashing the charging symbol that it always shows when you charge your tablet when its already shut down. I unplugged it and tried to open it but it wouldn't work and I'm panicking! Please, please, PLEASE tell me what I can do! Thanks!

Ps. I already tried to open it by pressing the power button, charging then trying to open, plug, unplug and pen. None of it worked!