Uses the camera of your phone to simulate the Black hole being 1m (3.28ft) away from you. Black hole mass here is similar to the mass of the planets like Mars or Earth. You can change the mass with the pinch gesture or slider. Allows you also to save the full-resolution photo of the Black Hole. Uses the real field of view angles from your phone's camera.
Requires only access for the camera and the SD card (to save high-resolution photos), nothing more. You can revoke the SD card access - it will be still usable, although with limited functionality. Number of ads = 0.
It is still on progress, I yet have to test on different-vendor phones and improve the 15 different translations - right now nearly all of them are generated by on-line auto translators which is far from perfect.
Credit for the "Black holes in fiction" article on the wikipedia for an image on a Creative commons licence.
Opening of the picture folder from within the app, might require some File Explorer App in the system.
Requires 32-bit floating point precision on GPU to render preview correctly.