Hello, you'll want to follow Apple's "Getting Processed Device-Motion Data" linked here: https://developer.apple.com/documentation/coremotion/getting_processed_device-motion_dataand pay special attention to this specific line in the above documentatation:self.motion.startDeviceMotionUpdates(using: .xMagneticNorthZVertical)The reference to .xMagneticNorthZVertical is one way that the iPhone can set its reference axis,see the helpful picture linked here for how the iPhone uses x, y, and z planes of rotation: https://developer.apple.com/documentation/coremotion/getting_raw_gyroscope_eventsAs you ask above, the z-axis when using .xMagneticNorthZVertical woulld actually be if you had your iPhone laying flat on a table and started spinning it like the hands of a clockWhat I think you may need in this case is the y value to sense the tilt (using .xMagneticNorthZVertical)I recommend printing out x, y, and z values in the console log and test this out (if you haven't already) and see how the .xMagneticNorthZVertical reference axis affects the values that print in the console log-- it took me a while to figure out how the iPhone recognizes which way its oriented too! Hope this helps

Dear poya, can't thank you enough!!! This works perfectly, don't know how I passed up this minor mistake so many times but I'm so thankful you pointed it out. Appreciate the help!

Hello, and thank you for your response, this helped me figure out what was going wrong.As you suggested, changing to system background color does indeed work correctly (with light appearance showing as white and dark appearance showing as black)However I found that I needed to click the checkmark for "High Contrast" in the assets folder when creating my custom light/dark background color asset- this fixed my specific problem and allowed the light appearance launchsreen for my app to appear the custom green, and the dark appearance to appear as the black.I updated the original post!