How to hard reboot the Nexus 7 (2013) when touchscreen is dysfunctional? I am using the Nexus 7 (2013) with the latest standard firmware from Google and today I encountered a weird problem.

When I turn the device on, the display lights up and all. I can also put it to sleep again. However, the touch screen does not work. Tilting the device also causes the automatic change from portrait to landscape mode and vice versa.

Holding down the power button brings up the "shutdown menu", but since the touchscreen isn't working, I cannot tell it to shut down. For the moment I am left to discharge the battery (it's also not sleeping automatically anymore, so it's faster) until it shuts down by itself gracefully or dies.

Any way of doing a hardware reset?

Connecting via USB doesn't help, because I have USB debugging disabled by default.
I'm not 100% sure about the Nexus 7, but with my Nexus 4, you can hold the Power button for a very long time (Something like 20 seconds) and it will hard-shutdown. This should help facilitate a hard reset and let you get into Fastboot or Recovery mode if you need to.