import SwiftUI

struct TapDemo: View {
  @State private var on = false
  var body: some View {
    VStack(spacing: 12) {
      Circle()
        .fill(on ? .green : .gray)
        .frame(width: 80, height: 80)
        .onTapGesture { on.toggle() }
      Text(on ? "On" : "Off")
    }
    .padding()
  }
}

                    

import SwiftUI

struct ContentView: View {
  var body: some View { TapDemo() }
}

                    

import SwiftUI

@main
struct MyApp: App {
  var body: some Scene {
    WindowGroup { ContentView() }
  }
}