Just upgraded my iPad Mini software and now it is stuck in a reboot and won't come on. Please help!

Hello.

I just noticed that a software update was available. I think it was iOS7. Did not really take note of what it was. But now my iPad Mini won't come on. it is stuck in a reboot and has been that way for at least an hour. Just tried to attach a picture of the screen without success.

If it was a phone, I'd have taken out the battery and just reinserted it but I can't do that with the iPad.

What can I do??? Please help!!!

Thank you.