High-fidelity iPhone app interface mockup for a sleep tracking app, one portrait phone screen centered on a soft dark background. The home screen shows a large sleep score ring at the top, a nightly sleep-stage bar chart below with deep sleep, light sleep and REM segments, and a row of small cards for bedtime, wake time and sleep debt. A bottom tab bar holds Home, Trends, Sounds and Profile icons. Calm deep-navy and lavender palette, clean sans-serif typography, generous spacing, consistent rounded cards, all visible text short and readable, no real brand logos, no placeholder lorem text, no distorted icons.