PowerToys/src/modules/launcher/PowerLauncher/App.xaml

<Application
    x:Class="PowerLauncher.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:ui="http://schemas.lepo.co/wpfui/2022/xaml"
    ShutdownMode="OnMainWindowClose"
    Startup="OnStartup">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ui:ThemesDictionary Theme="Dark" />
                <ui:ControlsDictionary />
                <ResourceDictionary Source="pack://application:,,,/Styles/Styles.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>