public abstract class Sandbox.UI.BaseStyles

public virtual void Add(Sandbox.UI.BaseStyles bs)

Copy over only the styles that are set.

public void ApplyCascading(Sandbox.UI.BaseStyles parent)

public virtual sealed object Clone()

Perform a deep copy of this stylesheet

public virtual void Dirty()

Called when any CSS properties are changed.

public void FillDefaults()

public virtual void From(Sandbox.UI.BaseStyles bs)

Copy all styles from given style set.

public virtual void FromLerp(Sandbox.UI.BaseStyles from, Sandbox.UI.BaseStyles to, float delta)

Lerp every property in this stylesheet

public virtual void LerpProperty(string name, Sandbox.UI.BaseStyles from, Sandbox.UI.BaseStyles to, float delta)

Lerp a specific property by name

public virtual bool Set(string property, string value)

Copy all styles from given style set.

public void SetRect(Sandbox.Rect r, float scale = 1)

Set Left, Right, Width and Height based on this rect. Scale can be used to scale the rect (maybe you want to use Panel.ScaleFromScreen etc)

public System.Nullable`1<Sandbox.UI.Align> Sandbox.UI.BaseStyles.AlignContent { get; set; }

Represents the `align-content` CSS property.

public System.Nullable`1<Sandbox.UI.Align> Sandbox.UI.BaseStyles.AlignItems { get; set; }

Represents the `align-items` CSS property.

public System.Nullable`1<Sandbox.UI.Align> Sandbox.UI.BaseStyles.AlignSelf { get; set; }

Represents the `align-self` CSS property.

public System.Nullable`1<float> Sandbox.UI.BaseStyles.AnimationDelay { get; set; }

Represents the `animation-delay` CSS property.

public string Sandbox.UI.BaseStyles.AnimationDirection { get; set; }

Represents the `animation-direction` CSS property.

public System.Nullable`1<float> Sandbox.UI.BaseStyles.AnimationDuration { get; set; }

Represents the `animation-duration` CSS property.

public string Sandbox.UI.BaseStyles.AnimationFillMode { get; set; }

Represents the `animation-fill-mode` CSS property.

public System.Nullable`1<float> Sandbox.UI.BaseStyles.AnimationIterationCount { get; set; }

Represents the `animation-iteration-count` CSS property.

public string Sandbox.UI.BaseStyles.AnimationName { get; set; }

Represents the `animation-name` CSS property.

public string Sandbox.UI.BaseStyles.AnimationPlayState { get; set; }

Represents the `animation-play-state` CSS property.

public string Sandbox.UI.BaseStyles.AnimationTimingFunction { get; set; }

Represents the `animation-timing-function` CSS property.

public System.Nullable`1<float> Sandbox.UI.BaseStyles.AspectRatio { get; set; }

Represents the `aspect-ratio` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackdropFilterBlur { get; set; }

Represents the `backdrop-filter-blur` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackdropFilterBrightness { get; set; }

Represents the `backdrop-filter-brightness` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackdropFilterContrast { get; set; }

Represents the `backdrop-filter-contrast` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackdropFilterHueRotate { get; set; }

Represents the `backdrop-filter-hue-rotate` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackdropFilterInvert { get; set; }

Represents the `backdrop-filter-invert` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackdropFilterSaturate { get; set; }

Represents the `backdrop-filter-saturate` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackdropFilterSepia { get; set; }

Represents the `backdrop-filter-sepia` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackgroundAngle { get; set; }

Represents the `background-angle` CSS property.

public string Sandbox.UI.BaseStyles.BackgroundBlendMode { get; set; }

Represents the `background-blend-mode` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.BackgroundColor { get; set; }

Represents the `background-color` CSS property.

public Sandbox.Texture Sandbox.UI.BaseStyles.BackgroundImage { get; set; }

public System.Nullable`1<bool> Sandbox.UI.BaseStyles.BackgroundPlaybackPaused { get; set; }

Controls whether the background video is paused. Mirrors `animation-play-state`. Maps to the CSS property `background-playback-state: paused | running`.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackgroundPositionX { get; set; }

Represents the `background-position-x` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackgroundPositionY { get; set; }

Represents the `background-position-y` CSS property.

public System.Nullable`1<Sandbox.UI.BackgroundRepeat> Sandbox.UI.BaseStyles.BackgroundRepeat { get; set; }

Represents the `background-repeat` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackgroundSizeX { get; set; }

Represents the `background-size-x` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BackgroundSizeY { get; set; }

Represents the `background-size-y` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.BackgroundTint { get; set; }

Represents the `background-tint` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.BorderBottomColor { get; set; }

Represents the `border-bottom-color` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderBottomLeftRadius { get; set; }

Represents the `border-bottom-left-radius` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderBottomRightRadius { get; set; }

Represents the `border-bottom-right-radius` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderBottomWidth { get; set; }

Represents the `border-bottom-width` CSS property.

public System.Nullable`1<Sandbox.UI.BorderImageFill> Sandbox.UI.BaseStyles.BorderImageFill { get; set; }

Represents the `border-image-fill` CSS property.

public System.Nullable`1<Sandbox.UI.BorderImageRepeat> Sandbox.UI.BaseStyles.BorderImageRepeat { get; set; }

Represents the `border-image-repeat` CSS property.

public Sandbox.Texture Sandbox.UI.BaseStyles.BorderImageSource { get; set; }

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.BorderImageTint { get; set; }

Represents the `border-image-tint` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderImageWidthBottom { get; set; }

Represents the `border-image-width-bottom` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderImageWidthLeft { get; set; }

Represents the `border-image-width-left` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderImageWidthRight { get; set; }

Represents the `border-image-width-right` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderImageWidthTop { get; set; }

Represents the `border-image-width-top` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.BorderLeftColor { get; set; }

Represents the `border-left-color` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderLeftWidth { get; set; }

Represents the `border-left-width` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.BorderRightColor { get; set; }

Represents the `border-right-color` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderRightWidth { get; set; }

Represents the `border-right-width` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.BorderTopColor { get; set; }

Represents the `border-top-color` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderTopLeftRadius { get; set; }

Represents the `border-top-left-radius` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderTopRightRadius { get; set; }

Represents the `border-top-right-radius` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.BorderTopWidth { get; set; }

Represents the `border-top-width` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.Bottom { get; set; }

Represents the `bottom` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.CaretColor { get; set; }

Represents the `caret-color` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.ColumnGap { get; set; }

Represents the `column-gap` CSS property.

public string Sandbox.UI.BaseStyles.Content { get; set; }

Represents the `content` CSS property.

public string Sandbox.UI.BaseStyles.Cursor { get; set; }

Represents the `cursor` CSS property.

public System.Nullable`1<Sandbox.UI.DisplayMode> Sandbox.UI.BaseStyles.Display { get; set; }

Represents the `display` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.FilterBlur { get; set; }

Represents the `filter-blur` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.FilterBorderColor { get; set; }

Represents the `filter-border-color` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.FilterBorderWidth { get; set; }

Represents the `filter-border-width` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.FilterBrightness { get; set; }

Represents the `filter-brightness` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.FilterContrast { get; set; }

Represents the `filter-contrast` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.FilterHueRotate { get; set; }

Represents the `filter-hue-rotate` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.FilterInvert { get; set; }

Represents the `filter-invert` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.FilterSaturate { get; set; }

Represents the `filter-saturate` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.FilterSepia { get; set; }

Represents the `filter-sepia` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.FilterTint { get; set; }

Represents the `filter-tint` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.FlexBasis { get; set; }

Represents the `flex-basis` CSS property.

public System.Nullable`1<Sandbox.UI.FlexDirection> Sandbox.UI.BaseStyles.FlexDirection { get; set; }

Represents the `flex-direction` CSS property.

public System.Nullable`1<float> Sandbox.UI.BaseStyles.FlexGrow { get; set; }

Represents the `flex-grow` CSS property.

public System.Nullable`1<float> Sandbox.UI.BaseStyles.FlexShrink { get; set; }

Represents the `flex-shrink` CSS property.

public System.Nullable`1<Sandbox.UI.Wrap> Sandbox.UI.BaseStyles.FlexWrap { get; set; }

Represents the `flex-wrap` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.FontColor { get; set; }

Represents the `font-color` CSS property.

public string Sandbox.UI.BaseStyles.FontFamily { get; set; }

Represents the `font-family` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.FontSize { get; set; }

Represents the `font-size` CSS property.

public System.Nullable`1<Sandbox.UI.FontSmooth> Sandbox.UI.BaseStyles.FontSmooth { get; set; }

Represents the `font-smooth` CSS property.

public System.Nullable`1<Sandbox.UI.FontStyle> Sandbox.UI.BaseStyles.FontStyle { get; set; }

Represents the `font-style` CSS property.

public System.Nullable`1<Sandbox.UI.FontVariantNumeric> Sandbox.UI.BaseStyles.FontVariantNumeric { get; set; }

Represents the `font-variant-numeric` CSS property.

public System.Nullable`1<int> Sandbox.UI.BaseStyles.FontWeight { get; set; }

Represents the `font-weight` CSS property.

public bool Sandbox.UI.BaseStyles.HasAnimation { get; set; }

Whether there is an active CSS animation.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.Height { get; set; }

Represents the `height` CSS property.

public System.Nullable`1<Sandbox.UI.ImageRendering> Sandbox.UI.BaseStyles.ImageRendering { get; set; }

Represents the `image-rendering` CSS property.

public System.Nullable`1<Sandbox.UI.Justify> Sandbox.UI.BaseStyles.JustifyContent { get; set; }

Represents the `justify-content` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.Left { get; set; }

Represents the `left` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.LetterSpacing { get; set; }

Represents the `letter-spacing` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.LineHeight { get; set; }

Represents the `line-height` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MarginBottom { get; set; }

Represents the `margin-bottom` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MarginLeft { get; set; }

Represents the `margin-left` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MarginRight { get; set; }

Represents the `margin-right` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MarginTop { get; set; }

Represents the `margin-top` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MaskAngle { get; set; }

Represents the `mask-angle` CSS property.

public Sandbox.Texture Sandbox.UI.BaseStyles.MaskImage { get; set; }

public System.Nullable`1<Sandbox.UI.MaskMode> Sandbox.UI.BaseStyles.MaskMode { get; set; }

Represents the `mask-mode` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MaskPositionX { get; set; }

Represents the `mask-position-x` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MaskPositionY { get; set; }

Represents the `mask-position-y` CSS property.

public System.Nullable`1<Sandbox.UI.BackgroundRepeat> Sandbox.UI.BaseStyles.MaskRepeat { get; set; }

Represents the `mask-repeat` CSS property.

public System.Nullable`1<Sandbox.UI.MaskScope> Sandbox.UI.BaseStyles.MaskScope { get; set; }

Represents the `mask-scope` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MaskSizeX { get; set; }

Represents the `mask-size-x` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MaskSizeY { get; set; }

Represents the `mask-size-y` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MaxHeight { get; set; }

Represents the `max-height` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MaxWidth { get; set; }

Represents the `max-width` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MinHeight { get; set; }

Represents the `min-height` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.MinWidth { get; set; }

Represents the `min-width` CSS property.

public string Sandbox.UI.BaseStyles.MixBlendMode { get; set; }

Represents the `mix-blend-mode` CSS property.

public System.Nullable`1<Sandbox.UI.ObjectFit> Sandbox.UI.BaseStyles.ObjectFit { get; set; }

Represents the `object-fit` CSS property.

public System.Nullable`1<float> Sandbox.UI.BaseStyles.Opacity { get; set; }

Represents the `opacity` CSS property.

public System.Nullable`1<int> Sandbox.UI.BaseStyles.Order { get; set; }

Represents the `order` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.OutlineColor { get; set; }

Represents the `outline-color` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.OutlineOffset { get; set; }

Represents the `outline-offset` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.OutlineWidth { get; set; }

Represents the `outline-width` CSS property.

public System.Nullable`1<Sandbox.UI.OverflowMode> Sandbox.UI.BaseStyles.Overflow { get; set; }

Represents the `overflow` CSS property.

public System.Nullable`1<Sandbox.UI.OverflowMode> Sandbox.UI.BaseStyles.OverflowX { get; set; }

Represents the `overflow-x` CSS property.

public System.Nullable`1<Sandbox.UI.OverflowMode> Sandbox.UI.BaseStyles.OverflowY { get; set; }

Represents the `overflow-y` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.PaddingBottom { get; set; }

Represents the `padding-bottom` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.PaddingLeft { get; set; }

Represents the `padding-left` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.PaddingRight { get; set; }

Represents the `padding-right` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.PaddingTop { get; set; }

Represents the `padding-top` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.PerspectiveOriginX { get; set; }

Represents the `perspective-origin-x` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.PerspectiveOriginY { get; set; }

Represents the `perspective-origin-y` CSS property.

public System.Nullable`1<Sandbox.UI.PointerEvents> Sandbox.UI.BaseStyles.PointerEvents { get; set; }

Represents the `pointer-events` CSS property.

public System.Nullable`1<Sandbox.UI.PositionMode> Sandbox.UI.BaseStyles.Position { get; set; }

Represents the `position` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.Right { get; set; }

Represents the `right` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.RowGap { get; set; }

Represents the `row-gap` CSS property.

public string Sandbox.UI.BaseStyles.SoundIn { get; set; }

Represents the `sound-in` CSS property.

public string Sandbox.UI.BaseStyles.SoundOut { get; set; }

Represents the `sound-out` CSS property.

public System.Nullable`1<Sandbox.UI.TextAlign> Sandbox.UI.BaseStyles.TextAlign { get; set; }

Represents the `text-align` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.TextBackgroundAngle { get; set; }

Represents the `text-background-angle` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.TextDecorationColor { get; set; }

Represents the `text-decoration-color` CSS property.

public System.Nullable`1<Sandbox.UI.TextDecoration> Sandbox.UI.BaseStyles.TextDecorationLine { get; set; }

Represents the `text-decoration-line` CSS property.

public System.Nullable`1<Sandbox.UI.TextSkipInk> Sandbox.UI.BaseStyles.TextDecorationSkipInk { get; set; }

Represents the `text-decoration-skip-ink` CSS property.

public System.Nullable`1<Sandbox.UI.TextDecorationStyle> Sandbox.UI.BaseStyles.TextDecorationStyle { get; set; }

Represents the `text-decoration-style` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.TextDecorationThickness { get; set; }

Represents the `text-decoration-thickness` CSS property.

public System.Nullable`1<Sandbox.Rendering.FilterMode> Sandbox.UI.BaseStyles.TextFilter { get; set; }

Represents the `text-filter` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.TextLineThroughOffset { get; set; }

Represents the `text-line-through-offset` CSS property.

public System.Nullable`1<Sandbox.UI.TextOverflow> Sandbox.UI.BaseStyles.TextOverflow { get; set; }

Represents the `text-overflow` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.TextOverlineOffset { get; set; }

Represents the `text-overline-offset` CSS property.

public System.Nullable`1<Color> Sandbox.UI.BaseStyles.TextStrokeColor { get; set; }

Represents the `text-stroke-color` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.TextStrokeWidth { get; set; }

Represents the `text-stroke-width` CSS property.

public System.Nullable`1<Sandbox.UI.TextTransform> Sandbox.UI.BaseStyles.TextTransform { get; set; }

Represents the `text-transform` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.TextUnderlineOffset { get; set; }

Represents the `text-underline-offset` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.Top { get; set; }

Represents the `top` CSS property.

public System.Nullable`1<Sandbox.UI.PanelTransform> Sandbox.UI.BaseStyles.Transform { get; set; }

Represents the `transform` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.TransformOriginX { get; set; }

Represents the `transform-origin-x` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.TransformOriginY { get; set; }

Represents the `transform-origin-y` CSS property.

public System.Nullable`1<Sandbox.UI.WhiteSpace> Sandbox.UI.BaseStyles.WhiteSpace { get; set; }

Represents the `white-space` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.Width { get; set; }

Represents the `width` CSS property.

public System.Nullable`1<Sandbox.UI.WordBreak> Sandbox.UI.BaseStyles.WordBreak { get; set; }

Represents the `word-break` CSS property.

public System.Nullable`1<Sandbox.UI.Length> Sandbox.UI.BaseStyles.WordSpacing { get; set; }

Represents the `word-spacing` CSS property.

public System.Nullable`1<int> Sandbox.UI.BaseStyles.ZIndex { get; set; }

Represents the `z-index` CSS property.