phone is black after charging all night

Hello MHSHOPE,

Thank you for using Apple Support Communities. Sounds like your iPhone 12 mini isn’t powering on. It just displays a blank screen. If so, we’d like to do our best to help out or possibly point you in the right direction for help.

First, you want to make sure your device is charged. If it has no battery life, it will not power on. This resource can guide you through steps you can follow to get your iPhone charged: If your iPhone or iPod touch won't charge - Apple Support

If your device charges slowly or won't charge

1.) Check your charging cable and USB adapter for signs of damage, like breakage or bent prongs. Don't use damaged accessories.

2.) Use a wall power outlet and check for firm connections between your charging cable, USB wall adapter, and wall outlet or AC power cable, or try a different outlet. 

3.) Remove any debris from the charging port on the bottom of your device, then firmly plug your charging cable into your device. If the charging port is damaged, your device probably needs service.

We also noticed that you're coming from the following resource here: If your iPhone won't turn on or is frozen - Apple Support

This is a great resource to review for when your iPhone will not power on. If charging your device and the resource you came from don't help you get your iPhone powered on, we strongly recommend that you reach out to Apple Support for help. They might have to physically evaluate your device. Just in case, you can use the following link to reach them: Get Support - Apple Support

Thank you for using Apple Support Communities. Best of luck.