iOS 13 and Swift 5.1
Color Hunt : choose your favorite color https://colorhunt.co/
Pixel Information about iOS devices https://www.paintcodeapp.com/news/ultimate-guide-to-iphone-resolutions
App Icon Generators https://appicon.co/#image-sets
What is pixel in assets 1x 2x 3x 1x is one point pixel 2x is four point pixel (2 time large) 3x is nine point pixel (3 times large)
Example : 100x100px 200x200px 300x300px
Create assets like icon, posts etc https://www.canva.com/