ContentView.swift

import SwiftUI

struct ContentView: View 
{
    @State var angle: CGFloat = 0

    let colors: [Color] = [ .red, .orange, .yellow, .green, .blue, .purple ]
    let columns = [ GridItem(.adaptive(minimum: 140), alignment: .leading) ]
    let animation = Animation.linear(duration: 10).repeatForever(autoreverses: false)

    var body: some View 
    {
        RoundedRectangle(cornerRadius: 25.0, style: .continuous)
        .fill(Color.red)
        .frame(width: 200, height: 200, alignment: .center)
        .shadow(color: .black, radius: 10, x: (angle) * 10, y: (angle) * 10)
        .onAppear 
        {
            withAnimation(animation)
            {
                angle = CGFloat.pi * 2
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider 
{
    static var previews: some View 
    {
        Group 
        {
            ContentView()
        }
    }
}