diff --git a/Icons/Demo.png b/Icons/Demo.png
index 32f8e1c..77ac2c2 100644
Binary files a/Icons/Demo.png and b/Icons/Demo.png differ
diff --git a/README.md b/README.md
index 430953e..2c631c1 100644
--- a/README.md
+++ b/README.md
@@ -135,7 +135,8 @@ If you want to use _Adwaita_ in a project, but there are widgets missing, open a
 | Syntax                          | Description                                                                             |
 | ------------------------------- | --------------------------------------------------------------------------------------- |
 | `keyboardShortcut(_:action:)`   | Create a keyboard shortcut available in one window.                                     |
-| `closeShortcut()`               | Create a keyboard shortcut for closing the window with "Ctrl + w". 
+| `closeShortcut()`               | Create a keyboard shortcut for closing the window with "Ctrl + w".                      |
+| `overlay(windows:)`             | Add windows that attach to a window of this type when being presented.                  |
 
 ### Menu Widgets
 | Name                 | Description                                                       | Widget                 |
diff --git a/user-manual/Basics/CreatingViews.md b/user-manual/Basics/CreatingViews.md
index 2210017..84b2a66 100644
--- a/user-manual/Basics/CreatingViews.md
+++ b/user-manual/Basics/CreatingViews.md
@@ -11,7 +11,7 @@ import Adwaita
 @main
 struct HelloWorld: App {
 
-    let id = "io.github.david-swift.HelloWorld"
+    let id = "io.github.david_swift.HelloWorld"
     var app: GTUIApp!
 
     var scene: Scene {
diff --git a/user-manual/Basics/HelloWorld.md b/user-manual/Basics/HelloWorld.md
index 69dfa46..2bf54ba 100644
--- a/user-manual/Basics/HelloWorld.md
+++ b/user-manual/Basics/HelloWorld.md
@@ -28,7 +28,7 @@ import Adwaita
 @main
 struct HelloWorld: App {
 
-    let id = "io.github.david-swift.HelloWorld"
+    let id = "io.github.david_swift.HelloWorld"
     var app: GTUIApp!
 
     var scene: Scene {
@@ -53,7 +53,7 @@ import Adwaita
 @main
 struct HelloWorld: App {
 
-    let id = "io.github.david-swift.HelloWorld"
+    let id = "io.github.david_swift.HelloWorld"
     var app: GTUIApp!
 
     var scene: Scene {
diff --git a/user-manual/Basics/KeyboardShortcuts.md b/user-manual/Basics/KeyboardShortcuts.md
index c92bfca..c9fe87e 100644
--- a/user-manual/Basics/KeyboardShortcuts.md
+++ b/user-manual/Basics/KeyboardShortcuts.md
@@ -26,7 +26,7 @@ import Adwaita
 @main
 struct HelloWorld: App {
 
-    let id = "io.github.david-swift.HelloWorld"
+    let id = "io.github.david_swift.HelloWorld"
     var app: GTUIApp!
 
     var scene: Scene {
@@ -52,7 +52,7 @@ import Adwaita
 @main
 struct HelloWorld: App {
 
-    let id = "io.github.david-swift.HelloWorld"
+    let id = "io.github.david_swift.HelloWorld"
     var app: GTUIApp!
 
     var scene: Scene {
diff --git a/user-manual/Basics/Windows.md b/user-manual/Basics/Windows.md
index 0c6c362..b1be6b1 100644
--- a/user-manual/Basics/Windows.md
+++ b/user-manual/Basics/Windows.md
@@ -14,7 +14,7 @@ Whenever the last one disappears, the app terminates.
 @main
 struct HelloWorld: App {
 
-    let id = "io.github.david-swift.HelloWorld"
+    let id = "io.github.david_swift.HelloWorld"
     var app: GTUIApp!
 
     var scene: Scene {
@@ -42,7 +42,7 @@ Another use case is showing a window:
 @main
 struct HelloWorld: App {
 
-    let id = "io.github.david-swift.HelloWorld"
+    let id = "io.github.david_swift.HelloWorld"
     var app: GTUIApp!
 
     var scene: Scene {
@@ -75,7 +75,7 @@ if you want to add and focus another instance of a window type:
 @main
 struct HelloWorld: App {
 
-    let id = "io.github.david-swift.HelloWorld"
+    let id = "io.github.david_swift.HelloWorld"
     var app: GTUIApp!
 
     var scene: Scene {
@@ -104,7 +104,7 @@ It's possible to customize how many windows are being presented at the app's sta
 @main
 struct HelloWorld: App {
 
-    let id = "io.github.david-swift.HelloWorld"
+    let id = "io.github.david_swift.HelloWorld"
     var app: GTUIApp!
 
     var scene: Scene {
@@ -127,4 +127,29 @@ struct HelloWorld: App {
 }
 ```
 
+## Add Modal Windows
+Modal windows are windows that attach to another window.
+Currently, it makes only sense to attach modal windows to windows that don't exist more than once.
+```swift
+@main
+struct HelloWorld: App {
+
+    let id = "io.github.david_swift.HelloWorld"
+    var app: GTUIApp!
+
+    var scene: Scene {
+        Window(id: "content") { _ in
+            // ...
+        }
+        // Add modal windows
+        .overlay {
+            Window(id: "overlay") { _ in
+                // ...
+            }
+        }
+    }
+
+}
+```
+
 [image-1]: ../../Icons/TwoWindows.png