htc 626 screen went black!!!

[AC Question]

htc 626 started randomly turning into a blinking rainbow for a few days, the screened timed out today and when i tried to unlock it it stayed black. i cannot restart or turn off power, i can do NOTHING. i hear everything else working properly. im hoping the screen isnt done for good. i have only had the phone about 6 months, it was not dropped or mishandled in any way