Specify an Area in a View — Swift UI

I am creating a game that allow the user to tap on specific area like a green dot. When the user tap on the dot, no reaction is shown. But if the user tap on positions outside the dot, an alert pops up.

I know how alert works, but I don’t know how to specify an area (the green dot) so that I can output an alert.

Thanks for advance if anyone can give me some hints ;p

I haven't tested but why not using a ZStack?

struct ExampleView: View {
    @State private var showAlert = false

    var body: some View {
        ZStack {
            Color.white
                .frame(maxWidth: .infinity, maxHeight: .infinity)
                .ignoresSafeArea()
                .onTapGesture {
                    showAlert.toggle()
                }
            Circle()
                .foregroundColor(Color.green)
                .frame(width: 120, height: 120)
        }
        .alert("Message", isPresented: $showAlert) {
            Button("Ok", role: .cancel, action: { })
        }
    }
}

Or maybe using the idea of @jnpdx?

struct OtherExampleView: View {
    @State private var showAlert = false

    var body: some View {
        VStack {
            Circle()
                .foregroundColor(Color.green)
                .frame(width: 120, height: 120)
                .background {
                    Color.white
                        .frame(maxWidth: .infinity, maxHeight: .infinity)
                        .ignoresSafeArea()
                        .onTapGesture {
                            showAlert.toggle()
                        }
                }
        }
        .alert("Message", isPresented: $showAlert) {
            Button("Ok", role: .cancel, action: { })
        }
    }
}

I'll test these two options tomorrow.