sleepy-launcher/ui/main.blp

using Gtk 4.0;
using Adw 1;

Adw.ApplicationWindow window {
    default-width: 900;
    default-height: 600;

    styles ["devel"]

    content: Gtk.Box {
        orientation: vertical;

        Adw.Leaflet leaflet {
            can-navigate-back: true;
            can-unfold: false;

            Gtk.Box {
                orientation: vertical;
                hexpand: true;

                name: "main";

                Adw.HeaderBar {
                    title-widget: Adw.WindowTitle {
                        title: "An Anime Game Launcher";
                    };
                }

                Adw.PreferencesPage {
                    Adw.PreferencesGroup {
                        Gtk.Image {
                            file: "assets/icon.png";
                            vexpand: true;
                            margin-top: 48;
                        }

                        Gtk.Label {
                            label: "An Anime Game Launcher";
                            margin-top: 32;

                            styles ["title-1"]
                        }
                    }

                    Adw.PreferencesGroup {
                        vexpand: true;
                        valign: center;

                        Gtk.Box {
                            halign: center;
                            margin-top: 64;
                            spacing: 8;

                            Adw.SplitButton launch_game {
                                label: "Launch";

                                hexpand: false;
                                width-request: 200;

                                styles ["suggested-action"]

                                popover: Gtk.Popover {
                                    Gtk.Button {
                                        label: "Launch in debug mode";
                                    }
                                };
                            }

                            Gtk.Button open_preferences {
                                icon-name: "preferences-system-symbolic";
                            }
                        }
                    }
                }
            }
        }
    };
}