UI Overlays System

public abstract partial class FullscreenOverlay<T> : WaveOverlayContainer, INamedOverlayComponent
    where T : OverlayHeader
{
    // Icon, title, and description for toolbar
    public virtual IconUsage Icon { get; }
    public virtual LocalisableString Title { get; }
    public virtual LocalisableString Description { get; }
    
    // Header component
    public T Header { get; private set; }
    
    // Color scheme
    protected readonly OverlayColourProvider ColourProvider;
    protected virtual Color4 BackgroundColour => ColourProvider.Background5;
    
    protected abstract T CreateHeader();
}

public enum OverlayColourScheme
{
    Purple,  // Default, settings
    Blue,    // Beatmap listing
    Pink,    // Profile, social
    Green,   // Changelog
    Orange,  // News
    Red,     // Multiplayer
    Aquamarine, // Rankings
    Lime,    // Chat
    Yellow,  // Wiki
    Plum,    // Tournament
}

[Cached]
public partial class HUDOverlay : Container, IKeyBindingHandler<GlobalAction>
{
    // Core HUD elements
    public readonly ModDisplay ModDisplay;
    public readonly HoldForMenuButton HoldToQuit;
    public readonly PlayerSettingsOverlay PlayerSettingsOverlay;
    
    // Controllers for HUD components
    private readonly ClicksPerSecondController clicksPerSecondController;
    public readonly InputCountController InputCountController;
    private readonly JudgementCountController judgementCountController;
    
    // Visibility control
    public Bindable<bool> ShowHud { get; } = new BindableBool();
    public Bindable<bool> ShowHealthBar = new Bindable<bool>(true);
    
    // Layout containers for non-skinnable elements
    public readonly FillFlowContainer TopLeftElements;
    public readonly FillFlowContainer TopRightElements;
    public readonly FillFlowContainer BottomRightElements;
    
    // Skinnable component containers
    private readonly SkinnableContainer mainComponents;
    private readonly SkinnableContainer rulesetComponents;
}

public enum HUDVisibilityMode
{
    Never,            // Always hidden
    HideDuringGameplay, // Hidden during active play
    Always            // Always visible
}

public class HUDComponentsContainer : SkinnableContainer
{
    public HUDComponentsContainer(GlobalSkinnableContainers target = GlobalSkinnableContainers.MainHUDComponents)
        : base(new GlobalSkinnableContainerLookup(target))
    {
        RelativeSizeAxes = Axes.Both;
        AlwaysPresent = true;
    }
}

public partial class SettingsOverlay : SettingsPanel, INamedOverlayComponent
{
    protected override IEnumerable<SettingsSection> CreateSections()
    {
        return new List<SettingsSection>
        {
            new GeneralSection(),
            new SkinSection(),
            new InputSection(createSubPanel(new KeyBindingPanel())),
            new UserInterfaceSection(),
            new GameplaySection(),
            new RulesetSection(),
            new AudioSection(),
            new GraphicsSection(),
            new OnlineSection(),
            new MaintenanceSection(),
            new DebugSection()
        };
    }
}

SettingsPanel (WIDTH = 600px)
├── Sidebar (200px)
│   └── Section buttons
└── ContentContainer (400px)
    ├── SearchTextBox
    ├── Sections
    └── Footer

public partial class NotificationOverlay : OsuFocusedOverlayContainer
{
    // Post a new notification
    public void Post(Notification notification);
    
    // Clear all notifications
    public void Clear();
}

// Simple notification
notifications.Post(new SimpleNotification
{
    Text = "Beatmap imported successfully",
    Icon = FontAwesome.Solid.Check
});

// Progress notification
var progress = new ProgressNotification
{
    Text = "Downloading beatmap...",
    CompletionText = "Download complete!",
    State = ProgressNotificationState.Active
};
notifications.Post(progress);

// Update progress
progress.Progress = 0.5f;
progress.Text = "Downloading beatmap... 50%";

// Complete
progress.State = ProgressNotificationState.Completed;

public partial class DialogOverlay : OsuFocusedOverlayContainer, IDialogOverlay
{
    // Show a dialog
    public void Push(PopupDialog dialog);
    
    // Get current dialog
    public PopupDialog CurrentDialog { get; }
}

public partial class MusicController : Container
{
    // Current track
    public IBindable<WorkingBeatmap> CurrentTrack { get; }
    
    // Playback control
    public void Play();
    public void Pause();
    public void Next();
    public void Previous();
    
    // Track position
    public void SeekTo(double position);
}

public interface IOverlayManager
{
    // Get overlay instance
    IBindable<OverlayActivation> OverlayActivationMode { get; }
    
    // Show/hide overlays
    void ShowOverlay<T>() where T : IOverlay;
    void HideOverlay<T>() where T : IOverlay;
    
    // Toggle overlay
    void ToggleOverlay<T>() where T : IOverlay;
}

public enum OverlayActivation
{
    All,          // All overlays can be shown
    UserTriggered, // Only user-triggered overlays
    Disabled      // No overlays allowed (e.g., during gameplay)
}

public partial class MyCustomOverlay : OsuFocusedOverlayContainer
{
    [BackgroundDependencyLoader]
    private void load()
    {
        RelativeSizeAxes = Axes.Both;
        
        Children = new Drawable[]
        {
            new Box
            {
                RelativeSizeAxes = Axes.Both,
                Colour = Color4.Black.Opacity(0.8f)
            },
            new Container
            {
                RelativeSizeAxes = Axes.Both,
                Padding = new MarginPadding(50),
                Child = new FillFlowContainer
                {
                    AutoSizeAxes = Axes.Y,
                    RelativeSizeAxes = Axes.X,
                    Direction = FillDirection.Vertical,
                    Spacing = new Vector2(20),
                    Children = new Drawable[]
                    {
                        new SpriteText
                        {
                            Text = "My Custom Overlay",
                            Font = OsuFont.GetFont(size: 30, weight: FontWeight.Bold)
                        },
                        new OsuButton
                        {
                            Text = "Close",
                            Action = Hide
                        }
                    }
                }
            }
        };
    }
    
    protected override void PopIn()
    {
        this.FadeIn(300, Easing.OutQuint);
    }
    
    protected override void PopOut()
    {
        this.FadeOut(300, Easing.OutQuint);
    }
}

public partial class MyFullscreenOverlay : FullscreenOverlay<MyOverlayHeader>
{
    public MyFullscreenOverlay()
        : base(OverlayColourScheme.Blue)
    {
    }
    
    [BackgroundDependencyLoader]
    private void load()
    {
        Child = new Container
        {
            RelativeSizeAxes = Axes.Both,
            Padding = new MarginPadding { Top = 50 },
            Child = new ScrollContainer
            {
                RelativeSizeAxes = Axes.Both,
                Child = new FillFlowContainer
                {
                    AutoSizeAxes = Axes.Y,
                    RelativeSizeAxes = Axes.X,
                    Direction = FillDirection.Vertical,
                    // Add content here
                }
            }
        };
    }
    
    protected override MyOverlayHeader CreateHeader() => new MyOverlayHeader();
}

public partial class MyOverlayHeader : OverlayHeader
{
    protected override OverlayTitle CreateTitle() => new MyOverlayTitle();
}

public partial class MyOverlayTitle : OverlayTitle
{
    public MyOverlayTitle()
    {
        Title = "My Overlay";
        Description = "A custom overlay example";
        Icon = FontAwesome.Solid.Star;
    }
}