Totally unresponsive? If so the only things you can do are reboot the phone, or boot into recovery and try clearing the system cache partition. Or a factory reset if nothing else works.
Or you could try booting into safe mode: it's unlikely, but if it works ok there it would tell you that one of your apps is the problem.
Though if none of that works and you have a usb otg adapter you could connect a mouse and control it that way (just to help fixing, not a permanent workaround of course!).
If you think an update was responsible then if there's a way of getting hold of the update and applying it manually that could also be tried (i.e. reinstall the update if you think there was a problem installing).
Just thinking aloud here - no diagnosis or cure, just a few things that occur to me.