Skins — where a Theme cannot reach

Method	Decides
`surface_box` · `floating_box` · `overlay_box`	Card and panel faces, floating surfaces, pills laid over the game or a map
`chip_box` · `chip_ink`	A chip's panel and the label colour that stays legible on it
`slot_box` · `slot_ink`	Quick-slot faces and their text
`disc_box`	The circle behind an avatar or badge
`alert_box` · `skeleton_box` · `segment_box`	Inline alerts, placeholders, segmented controls
`coach_ring_box`	The mark a coach tour puts around its target
`draw_joystick` · `draw_coach_pointer`	Things drawn directly — the joystick and its pointer
`divider_color` · `divider_thickness` · `section_box`	Dividers and section headings
`badge_box`	Quick-slot badges — quantity and time left
`progress_fill_box` · `notice_box` · `tint_notice`	Bar fills (outlined where a fill cannot reach 3:1 on its track) and snackbars

class_name MySkin extends GoSkin

func draw_joystick(canvas: CanvasItem, center: Vector2, knob: Vector2,
        radius: float, knob_radius: float, ink: Color, base: Color, active: bool) -> void:
    # The widget has already worked out the positions — only drawing happens here
    canvas.draw_circle(center, radius, Color(base, 0.4))
    canvas.draw_circle(knob, knob_radius, ink)

Shapes StyleBoxFlat cannot make

Class	What it draws
`GoStyleBoxCut`	Diagonally cut corners, one thickened accent edge, an outer glow
`GoStyleBoxBracket`	Corner marks only, leaving the content unenclosed
`GoStyleBoxMedieval`	A forged frame — rivets, corner engraving, a bevel highlight and iron, leather or parchment grain

All three serialise into a Theme resource like any other StyleBox — which is what lets a theme change shape.

Give padding through content_margin_*. Subclassing StyleBox in GDScript means _get_style_margin() is never called (measured on Godot 4.7). Fill the built-in fields or content will sit against the border.