Quick answer: Construct 3 Anchor behavior leaving UI in stale positions after window resize? Layout Viewport size mode and per-object anchor edges both matter.

Resizing the browser window stretches the layout but the HUD anchored to corners doesn’t reposition.

Layout Viewport Mode

Project Properties → Viewport size. Letterbox scale resizes to fit; Letterbox integer keeps pixel ratio. Anchor reads layout size; mode dictates layout size.

Per-Object Anchor Edges

Each Anchor behavior instance has Left/Right/Top/Bottom edge settings. For top-right HUD: Right = Anchor, Top = Anchor; others = Window. Behavior reads window dimensions and reflows.

Mobile Orientation Change

On mobile, orientation flips trigger viewport resize. Anchor handles it if configured. Test in landscape and portrait per build.

Update on Project Setting Change

Changing project Viewport mode after authoring may invalidate cached anchor positions. Re-save each layout to refresh.

Verifying

HUD elements stay anchored across window resize and mobile rotation. Letterbox bars appear where appropriate.

“Anchor needs the right edges per object plus the right viewport mode globally.”

Test resize behavior on different aspect ratios — ultrawide vs vertical mobile each catches different anchor edge bugs.