Little SwiftUI animation to fill the screen with red circle from the center of the screen

Explosion.swift

//
//  ContentView.swift
//  ExplosionView
//
//  Created by Paul Wood on 9/2/19.
//  Copyright © 2019 Paul Wood. All rights reserved.
//

import SwiftUI

struct ContentView: View {
  
  @State var willExplode = false
  
  struct ExplosionCircle: View {
    
    let proxy: GeometryProxy
    @Binding var willExplode: Bool
    
    var maximumTranslation: CGFloat {
      let centerPoint = CGPoint(x: proxy.size.width/2, y: proxy.size.height/2)
      let h = sqrt( centerPoint.y * centerPoint.y + centerPoint.x + centerPoint.x)
      let minimum = min(proxy.size.width, proxy.size.height)
      return h / minimum
    }

    var body: some View {
      Circle()
        .foregroundColor(Color.red)
        .scaleEffect(self.willExplode ? maximumTranslation : 0.0)
        .animation(.easeInOut(duration: 1.0))
        .aspectRatio(1, contentMode: .fill)
        .onAppear{
          self.willExplode  = true
        }
    }
  }
  
  var body: some View {
    GeometryReader { proxy in
      ExplosionCircle(proxy: proxy,
                      willExplode: self.$willExplode)
    }.edgesIgnoringSafeArea(.all)
  }
}

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