This theme require Android 7.1.1 ROM that fully support Substratum[OMS] and has installed the Substratum app (get it here https://play.google.com/store/apps/details?id=projekt.substratum)

Themed apps currently are:
- Android Framework
- Browser
- Calculator
- Camera
- Calendar AOSP
- CellBroadcast
- Chrome
- Contacts
- cLock
- DeskClock
- Dialer
- DocumentsUI / Files
- Development
- DU About
- Gallery
- Gmail
- Google App
- Google Contacts
- Google Clock
- Google Dialer
- Google Drive
- Google Hangout
- Google Keep
- Google Messenger
- Google Photos
- Google PlayStore
- Google PlayConsole
- Google Play Services
- Google Plus
- Google Wallpaper
- Inbox
- Instagram
- AOSP Keyboard
- Launcher3
- NavBars
- Settings
- Substratum
- SuperSU
- superuser
- SystemUI
- Telecom
- WhatsApp
and more to come.

Biohazard theme by pierx
Please use the Google+ community here https://goo.gl/BJHxg4 for bug report issue or suggestion.