Phone appears undamaged... screen just won't light up..

[AC Question]

can see it if I hold a flashlight at an angle on screen, and can tap to change screens.

 

[B. Diddy]

Welcome to Android Central! Which phone? It sounds like the backlight has failed, if it's a standard LCD-type screen--you'll probably have to bring it to a repair shop to fix it.

You didn't install any 3rd party screen dimming apps, did you?