game-ui-ux

SKILL.md

Game UI/UX

Build HUDs and menus that stay correct on a phone, an ultrawide monitor, and a TV across a
gamepad and a mouse. This skill owns the engine-neutral UI architecture — responsive layout,
scaling, focus navigation, screen flow, and how UI talks to game state — and defers the
concrete widget API to the engine UI skill.

When to use

Use when building a HUD (health/ammo/score), a menu (main/pause/settings), an inventory or
shop screen, or any overlay, and you want it to scale and navigate correctly.

Use to fix UI that breaks at other resolutions/aspect ratios, ignores notches/safe areas,
can't be used with a controller, or is wired to game state by per-frame polling.

Use to structure screen flow (title → game → pause → settings) as a stack, not flag soup.

When not to use: for the engine's concrete UI nodes/components and styling, use
godot-ui-control or Unity UI (UGUI/UI Toolkit). For visual punch (button pop, damage
numbers, shake) use game-feel. For branching conversation UI use dialogue-systems. For
translating UI strings, that is localization (see references/ and input-systems for
rebinding screens). For card/board layout specifics, the card-game genre composes this skill.

Core workflow

Pick a layout model: anchors + containers, never absolute pixels. Anchor elements to
edges/corners/center and let containers (rows, columns, grids) flow children. Absolute
(x, y) positions break at the first new resolution.

Choose a scaling strategy for the whole UI: a reference resolution that scales to fit
(most games), plus a policy for extra width/height on other aspect ratios (letterbox,
expand, or anchor HUD corners outward).

Respect the safe area. Inset critical UI from screen edges so notches, rounded corners,
and TV overscan don't clip it.

Make every screen keyboard/gamepad navigable. Set an initial focused control per screen,
define focus order/neighbors, and show a clear focus highlight. Mouse and focus must coexist.

Model screens as a stack. Push (pause over game), pop (resume), with input + visibility
handed to the top screen. This makes overlays and "back" trivial.

Drive the HUD from events, not polling. The HUD subscribes to health_changed,
score_changed, etc. and updates only when they fire — it does not read game state every
frame.

Verify across screens and devices. Resize the window, switch aspect ratios, unplug the
mouse and navigate by gamepad only, and confirm focus, scaling, and safe-area insets. Report
what you actually observed at which resolutions.

Patterns

1. Anchors + containers, not absolute coordinates

# Godot 4.7. Anchor a HUD label to the TOP-LEFT; let a container flow a row of hearts.
func _ready() -> void:
    $Score.set_anchors_preset(Control.PRESET_TOP_LEFT)   # sticks to the corner at any size
    # An HBoxContainer auto-lays-out children left-to-right; never position hearts by hand.
    for i in lives:
        $Hearts.add_child(make_heart())                   # HBoxContainer spaces them for you
# Unity 6.3 LTS uGUI: set RectTransform anchors to the corner; use a HorizontalLayoutGroup.
# RIGHT: anchors + layout groups. WRONG: rect.anchoredPosition = new Vector2(640, 360) (1080p-only).

2. Scale to a reference resolution (one UI, many screens)

# Godot 4.7 — Project Settings > Display > Window > Stretch:
#   Mode = "canvas_items", Aspect = "expand", reference size e.g. 1920x1080.
#   UI scales to the window; "expand" reveals extra space you anchor HUD corners into.
# Unity 6.3 LTS — Canvas > CanvasScaler:
#   UI Scale Mode = "Scale With Screen Size", Reference Resolution = 1920x1080,
#   Match = 0.5 (blend width/height) — pick 1.0 if your HUD is height-critical.

3. Safe-area inset for notches / overscan

# Godot 4.7. Inset a margin container to the OS-reported safe rect (phones, TVs).
func _apply_safe_area() -> void:
    var safe: Rect2i = DisplayServer.get_display_safe_area()
    var win := DisplayServer.window_get_size()
    $Margin.add_theme_constant_override("margin_left", safe.position.x)
    $Margin.add_theme_constant_override("margin_top",  safe.position.y)
    $Margin.add_theme_constant_override("margin_right", win.x - safe.end.x)
    $Margin.add_theme_constant_override("margin_bottom", win.y - safe.end.y)
# Unity 6.3 LTS: read Screen.safeArea (Rect in pixels) and set a panel's anchorMin/anchorMax to
# safeArea.position / (position+size) normalized by Screen.width/height.

4. Gamepad/keyboard focus (UI is unusable on a controller without it)

# Godot 4.7. Give each screen a default focus and wire neighbors so a stick/d-pad walks it.
func _on_screen_shown() -> void:
    $PlayButton.grab_focus()                               # always focus SOMETHING on open
$PlayButton.focus_neighbor_bottom = $SettingsButton.get_path()
$SettingsButton.focus_neighbor_top = $PlayButton.get_path()
# Unity 6.3 LTS: EventSystem.SetSelectedGameObject(playButton) on enable; set each Selectable's
# Navigation (Explicit or Automatic). RIGHT: a control is focused on open. WRONG: nothing
# selected → the gamepad does nothing and the player is stuck.

5. Event-driven HUD (decouple UI from game logic)

# RIGHT: HUD reacts to a signal; it updates only when health actually changes.
func _ready() -> void:
    player.health_changed.connect(_on_health_changed)     # emitted by gameplay
func _on_health_changed(current: int, max: int) -> void:
    $HealthBar.value = float(current) / max
# WRONG: func _process(dt): $HealthBar.value = player.hp / player.max_hp  # polls every frame,
# couples UI to the player's internals, and runs work even when nothing changed.

Pitfalls

Absolute pixel positions / a single design resolution. Looks right on your monitor, broken
everywhere else. Anchor to edges/center and flow with containers.

No aspect-ratio policy. 16:9-only layouts crop or letterbox badly on ultrawide and phones.
Decide expand vs letterbox and anchor HUD to corners that move outward.

Ignoring the safe area. HUD under a notch or lost to TV overscan. Inset critical elements.

No initial focus / no focus neighbors. The game is unplayable on a gamepad; players land
on a menu with nothing selected. Always focus one control and define navigation.

Polling game state in _process/Update. Couples UI to internals and wastes work. Push
updates via signals/events.

Tiny fixed font sizes. Unreadable on a TV-at-distance or a small phone. Scale text with the
UI and offer a text-size option.

Menu flow as boolean flags (isPaused, inSettings, …) becomes unmanageable. Use a
screen stack with push/pop.

Hardcoded English strings baked into layout. Translations overflow buttons. Externalize
strings and let containers size to content (see references/).

Mouse-only or focus-only. Support both; switching input device should not strand the user.

References

For stretch/scale modes per engine, the safe-area math, a complete focus-navigation and
screen-stack pattern, diegetic vs non-diegetic UI, accessibility (text size, contrast,
colorblind-safe state), and localization-ready layout, read references/layout-and-flow.md.

Related skills

godot-ui-control, Unity UI (UGUI/UI Toolkit) — the concrete widgets, themes, and styling.

game-feel — button pops, transitions, and HUD juice that ride on top of this layout.

dialogue-systems — conversation/choice UI that lives inside this UI shell.

input-systems — device switching, rebinding screens, and accessible controls.

rpg, card-game, tower-defense, visual-novel — UI-heavy genres that compose this skill.