diff --git a/.spi.yml b/.spi.yml
index 8ab4d49..82fa3bd 100644
--- a/.spi.yml
+++ b/.spi.yml
@@ -1,3 +1,4 @@
 version: 1
-external_links:
-    documentation: "https://david-swift.gitbook.io/adwaita"
\ No newline at end of file
+builder:
+  configs:
+    - documentation_targets: [Adwaita]
diff --git a/.swiftlint.yml b/.swiftlint.yml
index 062b47f..4a37d11 100644
--- a/.swiftlint.yml
+++ b/.swiftlint.yml
@@ -162,4 +162,5 @@ type_contents_order:
         - other_method
 
 excluded:
-    - Sources/Adwaita/View/Generated/
\ No newline at end of file
+    - Sources/Adwaita/View/Generated/
+    - Sources/Adwaita/Adwaita.docc/
diff --git a/Icons/Screenshot 2024-03-29 at 21.17.17.png b/Icons/Screenshot 2024-03-29 at 21.17.17.png
new file mode 100644
index 0000000..2570d8f
Binary files /dev/null and b/Icons/Screenshot 2024-03-29 at 21.17.17.png differ
diff --git a/Sources/Adwaita/Adwaita.docc/Adwaita.md b/Sources/Adwaita/Adwaita.docc/Adwaita.md
new file mode 100644
index 0000000..7be0585
--- /dev/null
+++ b/Sources/Adwaita/Adwaita.docc/Adwaita.md
@@ -0,0 +1,83 @@
+# ``Adwaita``
+
+_Adwaita for Swift_ is a framework for creating user interfaces for GNOME with an API similar to SwiftUI.
+
+## Overview
+
+Write user interfaces in a declarative way.
+
+As an example, the following code defines a _view_ (more information: ``View``).
+
+```swift
+struct Counter: View {
+
+    @State private var count = 0
+
+    var view: Body {
+        HStack {
+            Button(icon: .default(icon: .goPrevious)) {
+                count -= 1
+            }
+            Text("\(count)")
+                .style("title-1")
+                .frame(minWidth: 100)
+            Button(icon: .default(icon: .goNext)) {
+                count += 1
+            }
+        }
+    }
+
+}
+```
+
+A view can be implemented in different ways, the following screenshot showing an example.
+
+![Screenshot of the counter app](Counter.png)
+
+## Goals
+
+_Adwaita for Swift_'s main goal is to provide an easy-to-use interface for creating apps for the GNOME ecosystem.
+An article about the project's motivation is available on the [website of the Swift programming language](https://www.swift.org/blog/adwaita-swift/).
+
+## Installation
+
+### Dependencies
+
+#### Flatpak
+
+It is recommended to develop apps inside of a Flatpak.
+That way, you don't have to install Swift or any of the dependencies on your system, and you always have access to the latest versions.
+Take a look at the [template repository](https://github.com/AparokshaUI/AdwaitaTemplate).
+This works on Linux only.
+
+#### Directly on system
+
+You can also run your apps directly on the system.
+
+If you are using a Linux distribution, install `libadwaita-devel` or `libadwaita` (or something similar, based on the package manager) as well as `gtk4-devel`, `gtk4` or similar.
+
+On macOS, follow these steps:
+1. Install [Homebrew](https://brew.sh).
+2. Install Libadwaita (and thereby GTK 4):
+```
+brew install libadwaita
+```
+
+### Swift package
+1. Open your Swift package in GNOME Builder, Xcode, or any other IDE.
+2. Open the `Package.swift` file.
+3. Into the `Package` initializer, under `dependencies`, paste:
+```swift
+.package(url: "https://github.com/AparokshaUI/Adwaita", from: "0.1.0")   
+```
+
+## Template repository
+
+It is recommended to develop apps on Linux inside a Flatpak.
+Find more information in the [template repository](https://github.com/AparokshaUI/AdwaitaTemplate).
+
+## Topics
+
+### Tutorials
+
+- <doc:Table-of-Contents>
diff --git a/Sources/Adwaita/Adwaita.docc/CreatingViews.md b/Sources/Adwaita/Adwaita.docc/CreatingViews.md
new file mode 100644
index 0000000..99feae8
--- /dev/null
+++ b/Sources/Adwaita/Adwaita.docc/CreatingViews.md
@@ -0,0 +1,156 @@
+# Creating views
+
+Views are the building blocks of your application. 
+A view can be as simple as the ``Text`` widget, or as complex as the whole content of a single window.
+
+## Add views to a window
+You can add views to a window:
+```swift
+import Adwaita
+
+@main
+struct HelloWorld: App {
+
+    let id = "io.github.david_swift.HelloWorld"
+    var app: GTUIApp!
+
+    var scene: Scene {
+        Window(id: "content") { _ in
+            // These are the views:
+            HeaderBar.empty()
+            Text("Hello, world!")
+                .padding()
+        }
+    }
+
+}
+```
+
+In this example, the widgets ``HeaderBar`` and ``Text`` are used.
+`padding` is a view modifier, a function that modifies a view, which adds some padding around the text.
+
+## Create custom views
+While directly adding widgets into the `Window`'s body might work for very simple apps,
+it can get messy very quickly.
+Create custom views by declaring types that conform to the ``View`` protocol:
+```swift
+// A custom view named "ContentView":
+struct ContentView: View {
+
+    var view: Body {
+        HeaderBar.empty()
+        Text("Hello, world!")
+            .padding()
+    }
+
+}
+```
+
+## Properties
+As every structure in Swift, custom views can have properties:
+```swift
+struct HelloView: View {
+
+    // The property "text":
+    var text: String
+    var view: Body {
+        Text("Hello, \(text)!")
+            .padding()
+    }
+
+}
+```
+This view can be called via `HelloView(text: "world")` in another view.
+
+## State
+Whenever you want to modify a property that is stored in the view's structure from within your view,
+wrap the property with the ``State`` property wrapper:
+```swift
+struct MyView: View {
+
+    // This property can be modified form within the view:
+    @State private var text = "world"
+    var view: Body {
+        Text("Hello, \(text)!")
+            .padding()
+        Button("Change Text") {
+            text = Bool.random() ? "world" : "John"
+        }
+        .padding(10, .horizontal.add(.bottom))
+    }
+
+}
+```
+In this example, the text property is set whenever you press the "Change Text" button.
+
+## Change the state in child views
+You can access state properties in child views in the same way as you would access any other property
+if the child view cannot modify the state (`HelloView` is defined above):
+```swift
+struct MyView: View {
+
+    @State private var text = "world"
+    var view: Body {
+        // "HelloView" can read the "text" property:
+        HelloView(text: text)
+        Button("Change Text") {
+            text = Bool.random() ? "world" : "John"
+        }
+        .padding(10, .horizontal.add(.bottom))
+    }
+
+}
+```
+
+If the child view should be able to modify the state, use the ``Binding`` property wrapper in the child view
+and pass the property with a dollar sign (`$`) to that view.
+```swift
+struct MyView: View {
+
+    @State private var text = "world"
+    var view: Body {
+        HelloView(text: text)
+        // Pass the editable text property to the child view:
+        ChangeTextView(text: $text)
+    }
+
+}
+
+struct ChangeTextView: View {
+
+    // Accept the editable text property:
+    @Binding var text: String
+    var view: Body {
+        Button("Change Text") {
+            // Binding properties can be used the same way as state properties:
+            text = Bool.random() ? "world" : "John"
+        }
+        .padding(10, .horizontal.add(.bottom))
+    }
+
+}
+```
+
+If you have a more complex type and want to pass a property of the type as a binding,
+you can simply access the property on the binding.
+
+```swift
+HelloView(text: $complexType.text)
+```
+
+Whenever you modify a state property (directly or indirectly through bindings),
+the user interface gets automatically updated to reflect that change.
+
+## Save state values between app launches
+It's possible to automatically save a value that conforms to `Codable` whenever it changes to a file.
+The value in the file is read when the view containing the state value appears for the first time (e.g. when the user launches the app).
+
+Use the following syntax, where `"text"` is a unique identifier.
+```swift
+@State("text") private var text = "world"
+```
+
+You can organize your content by specifying a custom folder path which will be appended to the XDG data home directory.
+```swift
+@State("text", folder: "io.github.david_swift.HelloWorld/my-view") private var text = "world"
+```
diff --git a/Sources/Adwaita/Adwaita.docc/HelloWorld.tutorial b/Sources/Adwaita/Adwaita.docc/HelloWorld.tutorial
new file mode 100644
index 0000000..c2ef268
--- /dev/null
+++ b/Sources/Adwaita/Adwaita.docc/HelloWorld.tutorial
@@ -0,0 +1,82 @@
+@Tutorial {
+
+    @Intro(title: "The template") {
+        This is a beginner tutorial. It shows how to create a simple "Hello, world!" app using ``Adwaita``.
+        While there are instructions for building on macOS, _Adwaita for Swift_ works best on Linux.
+    }
+    
+    @Section(title: "Installation") {
+        @ContentAndMedia {
+            Learn how to set up your Linux system or your Mac.
+        }
+        @Steps {
+            @Step {
+                **If you are on Linux,** install the [GNOME Builder IDE](https://flathub.org/apps/org.gnome.Builder).
+                @Image(source: "Builder.png", alt: "GNOME Builder in the GNOME Software app store.")
+            }
+            @Step {
+                **If you are on macOS,** install [Xcode](https://developer.apple.com/xcode/).
+                Open your terminal client and follow the [installation instructions for Homebrew](https://brew.sh).
+                Then, run `brew install libadwaita`.
+                @Image(source: "InstallLibadwaita.png", alt: "The macOS Terminal application.")
+            }
+        }
+    }
+    
+    @Section(title: "Clone the template repository") {
+        @ContentAndMedia {
+            The template repository provides a simple, working app that can be used as a starting point for your own app.
+            In this section, you'll create a simple "Hello, world!" app and run the app.
+        }
+        @Steps {
+            @Step {
+                Open your terminal client and navigate to a directory you want to create the package in (e.g. `~/Documents/`).
+                @Image(source: "ChangeDirectory.png", alt: "The GNOME Console app.")
+            }
+            @Step {
+                Clone the template repository into the `HelloWorld` directory using `git clone https://github.com/AparokshaUI/AdwaitaTemplate HelloWorld`.
+                
+                This creates a directory `HelloWorld` containing the content of the [Adwaita Template](https://github.com/AparokshaUI/AdwaitaTemplate).
+                @Image(source: "GitClone.png", alt: "The GNOME Console app.")
+            }
+            @Step {
+                **If you are on Linux,** use the `Select a Folder...` button in the welcome window of GNOME Builder to open the `HelloWorld` directory.
+                
+                It will start to install the dependencies automatically.
+                @Image(source: "OpenFolder.png", alt: "GNOME Builder's welcome view.")
+            }
+            @Step {
+                **If you are on macOS,** use the `Open Existing Project...` button in the welcome window of Xcode to open the `HelloWorld` directory.
+                @Image(source: "OpenXcode.png", alt: "Xcode's welcome view.")
+            }
+            @Step {
+                Select the `Package.swift` file in the sidebar.
+                
+                This file defines that this Swift _package_ contains an executable, and lists the dependencies required by the executable.
+                One can see that the Swift files that are part of the executable are located in the `Sources` folder.
+                @Code(name: "Package.swift", file: "Package.swift")
+            }
+            @Step {
+                Open the `io.github.AparokshaUI.AdwaitaTemplate.json` file.
+                
+                This file is relevant for Linux only.
+                It informs the GNOME Builder about the required dependencies of your app, and how to build and install your app.
+                It is called a [Flatpak manifest](https://docs.flatpak.org/en/latest/manifests.html).
+                @Code(name: "io.github.AparokshaUI.AdwaitaTemplate.json", file: "io.github.AparokshaUI.AdwaitaTemplate.json")
+            }
+            @Step {
+                The `Sources` folder contains the actual Swift code of your app.
+                Open the `AdwaitaTemplate.swift` file to see the definition of an app and its user interface.
+                @Code(name: "AdwaitaTemplate.swift", file: "AdwaitaTemplate.swift")
+            }
+            @Step {
+                Run the app using the play button in Xcode or GNOME Builder.
+                A window should open.
+                
+                On macOS, the window will look slightly different from the one in the screenshot. Note that libadwaita is built for Linux and therefore works best on Linux.
+                @Image(source: "AdwaitaTemplate.png", alt: "The result.")
+            }
+        }
+    }
+
+}
diff --git a/Sources/Adwaita/Adwaita.docc/KeyboardShortcuts.md b/Sources/Adwaita/Adwaita.docc/KeyboardShortcuts.md
new file mode 100644
index 0000000..3fdb11b
--- /dev/null
+++ b/Sources/Adwaita/Adwaita.docc/KeyboardShortcuts.md
@@ -0,0 +1,115 @@
+# Keyboard shortcuts
+
+Keyboard shortcuts can be attached to individual windows or whole applications.
+
+## About keyboard shortcuts
+Keyboard shortcuts are represented as a `String`.
+You can add a single character by adding itself to the string, e.g. `"n"`.
+The F keys are written as `"F1"`, `"F2"`, etc.
+For character keys, write the lowercase name instead of the symbol, such as `"minus"` instead of `"-"`.
+
+Add modifiers to the shortcut using the following string modifiers:
+- `.shift()`
+- `.ctrl()`
+- `.alt()`
+- `.meta()`
+- `.super()`
+- `.hyper()`
+
+As an example, the following syntax represents the `Ctrl + N` shortcut: `"n".ctrl()`.
+
+## Add shortcuts to a window
+Add a keyboard shortcut to an invividual window. It is only available in that window.
+```swift
+import Adwaita
+
+@main
+struct HelloWorld: App {
+
+    let id = "io.github.david_swift.HelloWorld"
+    var app: GTUIApp!
+
+    var scene: Scene {
+        Window(id: "content") { _ in
+            HeaderBar.empty()
+            Text("Hello, world!")
+                .padding()
+        }
+        // Add the shortcut "Ctrl + W" for closing the window
+        .keyboardShortcut("w".ctrl()) { window in
+            window.close()
+        }
+    }
+
+}
+```
+
+## Add shortcuts to an app
+Add a keyboard to an app so that the shortcut is available in every top-level window.
+```swift
+import Adwaita
+
+@main
+struct HelloWorld: App {
+
+    let id = "io.github.david_swift.HelloWorld"
+    var app: GTUIApp!
+
+    var scene: Scene {
+        Window(id: "content") { _ in
+            HeaderBar.empty()
+            Text("Hello, world!")
+                .padding()
+        }
+        // Add the shortcut "Ctrl + Q" for terminating the app
+        .appKeyboardShortcut("q".ctrl()) { app in
+            app.quit()
+        }
+    }
+
+}
+```
+
+## Create shortcuts from a menu
+The most elegant way for adding keyboard shortcuts is in many cases adding them via menus.
+Here is an example using a menu button:
+```swift
+struct TestView: View {
+
+    var app: GTUIApp
+
+    var view: Body {
+        Menu(icon: .default(icon: .openMenu), app: app) {
+            MenuButton("New Window", window: false) {
+                app.addWindow("main")
+            }
+            // Add a keyboard shortcut to the app.
+            .keyboardShortcut("n".ctrl())
+        }
+    }
+
+}
+```
+Add the keyboard shortcut to a single window by specifying the `window` parameter in the initializer of `Menu`,
+and removing `window: false` in the initializer of `MenuButton`.
+
+## Create shortcuts from a button
+It's possible to easily create a keyboard shortcut from a button.
+Use `appKeyboardShortcut` instead of `keyboardShortcut` for shortcuts on an application level.
+Note that the shortcut gets activated after presenting the view for the first time.
+```swift
+struct HelloView: View {
+
+    var window: GTUIWindow
+
+    var view: Body {
+        Button("New Item") {
+            print("New Item")
+        }
+        // Add a keyboard shortcut to the window "window".
+        .keyboardShortcut("n".ctrl().shift(), window: window)
+    }
+
+}
+```
+
diff --git a/Sources/Adwaita/Adwaita.docc/Resources/AdwaitaIcon.png b/Sources/Adwaita/Adwaita.docc/Resources/AdwaitaIcon.png
new file mode 100644
index 0000000..66edf05
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diff --git a/Sources/Adwaita/Adwaita.docc/Resources/AdwaitaTemplate.swift b/Sources/Adwaita/Adwaita.docc/Resources/AdwaitaTemplate.swift
new file mode 100644
index 0000000..823eff7
--- /dev/null
+++ b/Sources/Adwaita/Adwaita.docc/Resources/AdwaitaTemplate.swift
@@ -0,0 +1,23 @@
+// The Swift Programming Language
+// https://docs.swift.org/swift-book
+
+import Adwaita
+
+@main
+struct AdwaitaTemplate: App {
+
+    let id = "io.github.AparokshaUI.AdwaitaTemplate"
+    var app: GTUIApp!
+
+    var scene: Scene {
+        Window(id: "main") { window in
+            Text(Loc.helloWorld)
+                .padding()
+                .topToolbar {
+                    ToolbarView(app: app, window: window)
+                }
+        }
+        .defaultSize(width: 450, height: 300)
+    }
+
+}
diff --git a/Sources/Adwaita/Adwaita.docc/Resources/Counter.png b/Sources/Adwaita/Adwaita.docc/Resources/Counter.png
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index 0000000..06247b8
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diff --git a/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/AdwaitaTemplate.png b/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/AdwaitaTemplate.png
new file mode 100644
index 0000000..f1b19a2
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diff --git a/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/Builder.png b/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/Builder.png
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index 0000000..b8d0442
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diff --git a/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/ChangeDirectory.png b/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/ChangeDirectory.png
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index 0000000..952a56f
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diff --git a/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/GitClone.png b/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/GitClone.png
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index 0000000..a05d977
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diff --git a/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/InstallLibadwaita.png b/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/InstallLibadwaita.png
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index 0000000..313f3f6
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diff --git a/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/OpenFolder.png b/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/OpenFolder.png
new file mode 100644
index 0000000..2de90db
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diff --git a/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/OpenXcode.png b/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/OpenXcode.png
new file mode 100644
index 0000000..df02ffe
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diff --git a/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/Package.swift b/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/Package.swift
new file mode 100644
index 0000000..5b0f9d9
--- /dev/null
+++ b/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/Package.swift
@@ -0,0 +1,31 @@
+// swift-tools-version: 5.8
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "Adwaita Template",
+    platforms: [
+        .macOS(.v13)
+    ],
+    dependencies: [
+        .package(url: "https://github.com/AparokshaUI/Adwaita", from: "0.2.0"),
+        .package(url: "https://github.com/AparokshaUI/Localized", from: "0.2.0")
+    ],
+    targets: [
+        .executableTarget(
+            name: "AdwaitaTemplate",
+            dependencies: [
+                .product(name: "Adwaita", package: "Adwaita"),
+                .product(name: "Localized", package: "Localized")
+            ],
+            path: "Sources",
+            resources: [
+                .process("Localized.yml")
+            ],
+            plugins: [
+                .plugin(name: "GenerateLocalized", package: "Localized")
+            ]
+        )
+    ]
+)
diff --git a/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/io.github.AparokshaUI.AdwaitaTemplate.json b/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/io.github.AparokshaUI.AdwaitaTemplate.json
new file mode 100644
index 0000000..6ee9059
--- /dev/null
+++ b/Sources/Adwaita/Adwaita.docc/Resources/HelloWorld/io.github.AparokshaUI.AdwaitaTemplate.json
@@ -0,0 +1,52 @@
+{
+  "app-id": "io.github.AparokshaUI.AdwaitaTemplate",
+  "runtime": "org.gnome.Platform",
+  "runtime-version": "46",
+  "sdk": "org.gnome.Sdk",
+  "sdk-extensions": [
+    "org.freedesktop.Sdk.Extension.swift5"
+  ],
+  "command": "AdwaitaTemplate",
+  "finish-args": [
+    "--share=ipc",
+    "--socket=fallback-x11",
+    "--device=dri",
+    "--socket=wayland"
+  ],
+  "build-options": {
+    "append-path": "/usr/lib/sdk/swift5/bin",
+    "prepend-ld-library-path": "/usr/lib/sdk/swift5/lib"
+  },
+  "cleanup": [
+    "/include",
+    "/lib/pkgconfig",
+    "/man",
+    "/share/doc",
+    "/share/gtk-doc",
+    "/share/man",
+    "/share/pkgconfig",
+    "*.la",
+    "*.a"
+  ],
+  "modules": [
+    {
+      "name": "AdwaitaTemplate",
+      "builddir": true,
+      "buildsystem": "simple",
+      "sources": [
+        {
+          "type": "dir",
+          "path": "."
+        }
+      ],
+      "build-commands": [
+        "swift build -c release --static-swift-stdlib",
+        "install -Dm755 .build/release/AdwaitaTemplate /app/bin/AdwaitaTemplate",
+        "install -Dm644 data/io.github.AparokshaUI.AdwaitaTemplate.metainfo.xml $DESTDIR/app/share/metainfo/io.github.AparokshaUI.AdwaitaTemplate.metainfo.xml",
+        "install -Dm644 data/io.github.AparokshaUI.AdwaitaTemplate.desktop $DESTDIR/app/share/applications/io.github.AparokshaUI.AdwaitaTemplate.desktop",
+        "install -Dm644 data/icons/io.github.AparokshaUI.AdwaitaTemplate.svg $DESTDIR/app/share/icons/hicolor/scalable/apps/io.github.AparokshaUI.AdwaitaTemplate.svg",
+        "install -Dm644 data/icons/io.github.AparokshaUI.AdwaitaTemplate-symbolic.svg $DESTDIR/app/share/icons/hicolor/symbolic/apps/io.github.AparokshaUI.AdwaitaTemplate-symbolic.svg"
+      ]
+    }
+  ]
+}
diff --git a/Sources/Adwaita/Adwaita.docc/Table of Contents.tutorial b/Sources/Adwaita/Adwaita.docc/Table of Contents.tutorial
new file mode 100644
index 0000000..a645450
--- /dev/null
+++ b/Sources/Adwaita/Adwaita.docc/Table of Contents.tutorial	
@@ -0,0 +1,13 @@
+@Tutorials(name: "Develop Apps for GNOME") {
+
+    @Intro(title: "Develop Apps for GNOME") {
+        Learn the basics of _Adwaita for Swift_ to create beautiful apps for the GNOME desktop.
+    }
+
+    @Chapter(name: "Adwaita for Swift essentials") {
+        Get to know the most important principles of the _Adwaita for Swift_ framework.
+        @TutorialReference(tutorial: "doc:HelloWorld")
+        @Image(source: "AdwaitaIcon.png", alt: "The Adwaita for Swift icon.")
+    }
+
+}
diff --git a/Sources/Adwaita/Adwaita.docc/Windows.md b/Sources/Adwaita/Adwaita.docc/Windows.md
new file mode 100644
index 0000000..186fdb1
--- /dev/null
+++ b/Sources/Adwaita/Adwaita.docc/Windows.md
@@ -0,0 +1,137 @@
+# Windows
+
+Windows in _Adwaita_ are not actually single windows in the user interface,
+but rather instructions on how to create one type of window.
+
+## The simplest case
+A single window app is an app having exactly one window, and when this window is closed, the app terminates.
+We can add multiple windows to an app as well. 
+Whenever the last one disappears, the app terminates.
+```swift
+@main
+struct HelloWorld: App {
+
+    let id = "io.github.david_swift.HelloWorld"
+    var app: GTUIApp!
+
+    var scene: Scene {
+        Window(id: "content") { _ in
+            HeaderBar.empty()
+            Text("Hello, world!")
+                .padding()
+        }
+        // Add a second window:
+        Window(id: "window-2") { _ in
+            HeaderBar.empty()
+            Text("Window 2")
+                .padding()
+        }
+    }
+
+}
+```
+
+## Showing windows
+Every app contains the property `app`. 
+You can use this property for running functions that affect the whole app, e.g. quitting the app.
+Another use case is showing a window:
+```swift
+@main
+struct HelloWorld: App {
+
+    let id = "io.github.david_swift.HelloWorld"
+    var app: GTUIApp!
+
+    var scene: Scene {
+        Window(id: "content") { _ in
+            HeaderBar.empty()
+            Text("Hello, world!")
+                .padding()
+        }
+        Window(id: "control") { _ in
+            HeaderBar.empty()
+            Button("Show Window") {
+                // Show the window with the identifier "content":
+                app.showWindow("content")
+            }
+            .padding()
+        }
+    }
+
+}
+```
+"Showing" a window means creating an instance of the window type if there isn't one,
+or focusing the window that already exists of that type otherwise.
+It should be used for opening windows that cannot be presented more than once
+and for moving a window that is already open into the foreground.
+
+## Adding windows
+You can call the `addWindow(_:parent:)` function instead of `showWindow(_:)`
+if you want to add and focus another instance of a window type:
+```swift
+@main
+struct HelloWorld: App {
+
+    let id = "io.github.david_swift.HelloWorld"
+    var app: GTUIApp!
+
+    var scene: Scene {
+        Window(id: "content") { _ in
+            HeaderBar.empty()
+            Text("Hello, world!")
+                .padding()
+        }
+        Window(id: "control") { _ in
+            HeaderBar.empty()
+            Button("Add Window") {
+                // Add a new instance of the "content" window type
+                app.addWindow("content")
+            }
+            .padding()
+        }
+    }
+
+}
+```
+It can be used to add an overlay window to a certain instance of a window type
+by specifying the `parent` parameter, e.g. in the example above:
+```swift
+Window(id: "control") { window in
+    HeaderBar.empty()
+    Button("Add Child Window") {
+        // Add the new instance as a child window of this window
+        app.addWindow("content", parent: window)
+    }
+    .padding()
+}
+```
+
+## Customizing the initial number of windows
+By default, every window type of the app's scene appears once when the app starts.
+It's possible to customize how many windows are being presented at the app's startup:
+```swift
+@main
+struct HelloWorld: App {
+
+    let id = "io.github.david_swift.HelloWorld"
+    var app: GTUIApp!
+
+    var scene: Scene {
+        // Open no window of the "content" type
+        Window(id: "content", open: 0) { _ in
+            HeaderBar.empty()
+            Text("Hello, world!")
+                .padding()
+        }
+        // Open two windows of the "control" type
+        Window(id: "control", open: 2) { _ in
+            HeaderBar.empty()
+            Button("Show Window") {
+                app.addWindow("content")
+            }
+            .padding()
+        }
+    }
+
+}
+```