iOS UI Design principles
There are three primary principles to follow while designing an app for iOS.
Clarity. Throughout the system, text is legible at every size, icons are precise and lucid, adornments are subtle and appropriate, and a sharpened focus on functionality motivates the design. Negative space, color, fonts, graphics, and interface elements subtly highlight important content and convey interactivity.
Deference. Fluid motion and a crisp, beautiful interface help people understand and interact with content while never competing with it. Content typically fills the entire screen, while translucency and blurring often hint at more. Minimal use of bezels, gradients, and drop shadows keep the interface light and airy, while ensuring that content is paramount.
Depth. Distinct visual layers and realistic motion convey hierarchy, impart vitality, and facilitate understanding. Touch and discoverability heighten delight and enable access to functionality and additional content without losing context. Transitions provide a sense of depth as you navigate through content.
Three primary principles applied on Instagram app for iOS
Text and font size is easy to read and consistent.
Visualization is clean, Icons and navigation is user friendly
Image is bigger and centred.
Distinct visual layers and realistic motion convey hierarchy
While designing an app the communication between user and the app should be clean. Focus on clarity, text should be clear, the font including the font size and colour should be visible. The content should be aligned and centred properly. Navigation should be life like experience, layers should be separate, informative and functional to help user be oriented.