s&box

State<T> + Track<T>( initial ) on both GooPanel and Cell. Auto-dirtying state for mutation outside event handlers (timers, network, polls): writing a different Value marks the owner dirty, no manual Rebuild()
Each.Of( items, builder ) / Each.Of( items, keyOf, builder ) plus a Children.Add overload for it: keyed list building inline in a Children = { ... } initializer instead of a separate AddRange call
Children.Add( in T? child ): nullable-child overload, the conditional-child idiom that replaces AddIf
Layout.Stack() and Layout.Layer( child ) with overloads for Container, Sector, Arc, and Polygon
Hud.ScrollArea, Hud.DismissScrim, Hud.FillRect: factories for the three most common test case patterns (bounded-height scroll triple, invisible dismiss click-catcher, absolute left-anchored fill bar)
Controls.Slider optional palette params: trackColor, fillColor, thumbColor
Viewport.CenterOn( world, screenPoint ): pin a world position to a given screen point
Perf: opt-in live pipeline profiler (Perf.Enabled, Report(), Reset())

Cell.Mount no longer allocates when seed and configure are both null.
Variant application is gated on raw inputs: identical variant inputs skip the StringBuilder and rgba string work, so per-frame style writes on variant-carrying panels no longer pay a CSS build per pass

Removed Children.AddIf( condition, child ). Replace with the new nullable Add: children.Add( cond ? child : null )

Native reactive UI particles via Hud.Particles / ParticleField
GPU SDF arbitrary-polygon shapes (points-texture packing), plus a stable-identity AddRange overload for keyed lists Position/offsets, PointerEvents and BorderRadius exposed on Scene, Svg and Web panels
Controls.Popover(open, trigger, content, anchor, onDismiss, gap, key) helper for controlled anchored popover (Top / Bottom / Left / Right / BelowStart) with click-away light-dismiss - adjacent to the engine's Sandbox.UI.Popup and BasePopup

Unified the shape surface onto GPU SDF: Sector, Arc and Polygon all render via SDF. Included ui_shape.shader for this functionality
All shapes gained HoverBackgroundColor + TransitionMs, with outline-accurate true mouse enter/leave gating across every Stateful panel
Style resolution is now last-declared-wins (was first-wins)

Please make sure if you are using this, update your code: Controls.DisabledOpacity moved to Container.DisabledOpacity

ShaderEffect refactor: construct from a shader path with an indexer uniform bag.
Uniforms accept per-frame functions and a built-in clock:
Hud.Overlay() - full-screen HUD root column layout, pointer-through (does not swallow game input)
Hud.Fill() - absolute layer, pointer-through; the standard Hud for shader effects
Hud.Scrim(color) - edge-pinned tinted backdrop for modals. PointerEvents left to the caller so it can toggle on open/close
Hud.Wallpaper(texture, path) - background image layer by texture or by path
Hud.Anchored(anchor, content, padding) - pins content to a screen corner or edge center, pointer-through
Hud.Spacer() - flex-grow gap that pushes siblings apart
Hud.Divider(color) - 1px full-width horizontal rule. low-alpha white by default.
Controls.Button(...) ready-made button and Children.AddIf(condition, child)
Container.Disabled forces pointer-off and dims, per node, applied after state variants.
Container.SwallowClick stops a click from bubbling
PointerDrag frame-polled move/resize helper, UI-scale correct via Current(panel)
PaddingX/Y
MarginX/Y
BorderTopRadius
BorderBottomRadius
BorderLeftRadius
BorderRightRadius
All 9 animation dampers gain Tick(dt).
KeyTracker.Pressed(name) rising-edge query.
Text.Style takes a TextStyle bundle for one-shot font blocks.
Cell.Mount<TCell>(key, seed, configure): seed runs once at first mount, configure every rebuild.
Image gains a positioning subset and defaults BackgroundRepeat to NoRepeat, stopping ObjectFit.Contain tiling

ShaderEffect materials are created on the main thread (fixes a render-thread crash)
Disabled styling is applied after state variants so it wins over hover/active.
Theme motion tokens (MotionFast/Base/Slow) are ints, removed casts.

Fixed pointer events for children being null instead of none, preventing pop-ups from appearing when mousing over the text itself
Fixed stylesheet bleed reconciliation
Fixed nullable warnings and suppressed some noisy CS warnings

Cleaning the repo of examples -- will author examples a different way (~6MB to ~500kb)