Given this SwiftUI code snippet, what will happen when the button toggles isExpanded?

Given this SwiftUI code snippet, what will happen when the button toggles isExpanded?

struct ContentView: View {
  @Namespace var ns
  @State var isExpanded = false
  var body: some View {
    VStack {
      if isExpanded {
        RoundedRectangle(cornerRadius: 25)
          .matchedGeometryEffect(id: "shape", in: ns)
          .frame(width: 300, height: 300)
      } else {
        RoundedRectangle(cornerRadius: 25)
          .matchedGeometryEffect(id: "shape", in: ns)
          .frame(width: 100, height: 100)
      }
      Button("Toggle") { isExpanded.toggle() }
    }
  }
}