Black screen during update, now nothing after reboot

I was trying to update my iMac to the latest software update, and after a moment the screen went completely dark. I waited for a while and nothing. I thought maybe the iMac shut off after the update, so I tried pressing the power button, and that actually powered it off (I assume that interrupted the update). I have a microphone with a power light that I plugged in so I could tell if my iMac was powered “on” or not, but nothing is happening on screen. I tried a few keyboard commands after turning the computer back on (shift, Command L, Command Option P R, Command R) and still no results. I assume the software update didn’t finish and now I’m not really sure what to do.