Gradients

In review

Gradients in Nockerl are purposeful, not decorative. They appear in a few specific, codified places and never as a generic background wash. Every one is a static fill, never a colored glow, never tweened between two fills. All stops are color tokens, so a gradient re-themes light/dark by construction and carries no hardcoded hex.

Where gradients are allowed

There are exactly four sanctioned gradients. Each is a fixed recipe (angle + token stops), mirrored across web, Android, and Swift.

1. The accent fill: a two-stop vertical cyan

The primary fill that runs the whole accent ladder. A top-down (180deg) cyan gradient whose lighter top stop reads as a catch-light, exactly like a surface lit from above:

background: linear-gradient(180deg, var(--color-accent-primary-hi), var(--color-accent-primary));

Stop	Token	Dark	Light
top (catch-light)	--color-accent-primary-hi	#2EC9E4	#2BA0BD
bottom (brand)	--color-accent-primary	#0CC0DF (cyan-500)	#0891B2 (cyan-700)

The bottom stop is the brand anchor; -hi is a lighter cyan defined solely as “the lit-from-above top of a primary fill gradient.” This one recipe is shared verbatim by the primary Button, and the filled/ON states of Switch, Checkbox, RadioGroup, SegmentedControl, Stepper, and the ProgressTrack bar. One fill, one place to change it. It always ships with a top surface-highlight inset and a neutral drop shadow (see the elevation law), never a colored glow.

2. The elevated-surface sheen: surface2 → surface1

Floating surfaces (menus, popovers, and other lifted panels) fill with a subtle top-down lightening from the next surface tone down to the card tone, which reads as a gentle sheen on a raised panel:

background: linear-gradient(180deg, var(--color-card-surface2), var(--color-card-surface1));

Stop	Token	Dark
top	--color-card-surface2	#333942
bottom	--color-card-surface1	#2C313A

The base card is a flat fill, not a gradient

A resting Surface / Card fills with a flat --color-card-surface1: lift comes from the shadow + top catch-light, not a gradient. The surface2 → surface1 gradient is reserved for floating surfaces (Menu, Popover), where it out-specifies the flat .nk-surface fill to give a raised panel its extra sheen.

3. The ground top-light: a dark-only radial wash

The dark app ground is lit from above by a single large, off-center radial that fades to the near-black canvas. It is a page-level light, not a brand color:

background:
  radial-gradient(1100px 600px at 82% -8%, #12161b, transparent 60%),
  var(--color-canvas);

Applied to body in the dark theme only; in the light theme --color-canvas resolves to a flat neutral ground and no wash is painted. The wash itself is a barely-lighter neutral (#12161b over the dark --color-canvas, #0A0B0D), again a catch-light read, not an emission.

4. The faceted field: the Nockerl signature backdrop

The low-poly faceted field is the Nockerl signature surface: a jittered triangle mesh (the Nockerl mark is a triangle) whose facet luminance drifts in a slow diagonal tone-wave so the field is “active, not busy.” It is not a CSS gradient. It is a token-colored <canvas> that paints a flat ground, then re-tints each facet per frame. It has one codified look: no intensity / density / speed knobs and no variants.

It lives in one primitive, FacetedBackground (site/src/components/primitives/FacetedBackground.tsx), which is the web mirror of the two shipped native implementations, the canonical truth being Android:

• Android (canonical): chat/ui/ChatFeedBackground.kt (Compose Canvas)
• Voice (Swift port): UI/FacetBackground.swift (SwiftUI Canvas)

Every visual parameter is a frozen constant pulled 1:1 from those native sources. Editing the look means editing these in lock-step everywhere. There is deliberately no runtime control, so the field looks identical on every platform by construction:

Constant	Value	Native name	Role
CELL_PX	128	FACET_CELL_SIZE (128.dp; Swift port 130)	mesh cell size
JITTER_FRACTION	0.34	n/a	point stray as a fraction of the cell
STATIC_JITTER	0.022	STATIC_FACET_JITTER	baked per-facet tonal grain
AMPLITUDE	0.05	WAVE_AMPLITUDE	peak tone-wave luminance swing
PERIOD_MS	18000	WAVE_PERIOD_MILLIS	one full diagonal wave cycle (~18s)
EDGE_WIDTH	0.75	n/a	facet hairline width (device px)
EDGE_ALPHA	0.05	EDGE_ALPHA	barely-there facet hairline

Color is token-only: the canvas reads the live computed --color-chat-bg (facet base, #181B20 dark) and --color-canvas-edge (hairline, #2A2D33 dark) via getComputedStyle, so a token edit re-tints the whole field and it themes light/dark. The mesh is built from a deterministic hash (jitter01) so it never re-rolls or shimmers, and each cell’s diagonal alternates by (col+row) parity so the field never looks like a striped lattice.

How it animates without breaking the static-fill law: the fill is never tweened. Each frame the canvas re-tints existing facets by a cheap per-channel luminance add (AMPLITUDE · sin(phase + facet.diagonalPos · 2π) plus the facet’s baked staticDelta), which is hue-preserving, so facets stay neutral. This is the same trick as Compose drawPath / SwiftUI Canvas: paint, don’t interpolate a Brush.

The static-fill law

All four gradients obey design law 7 (motion):

• Gradients are static fills. Feedback never tweens between two gradients: a gradient swap can’t interpolate in CSS or Compose Brush; it hard-cuts and flashes. State feedback rides on brightness, transform, and shadow over the top. (The primary Button, for example, keeps its fill fixed and animates filter: brightness() + translateY + a neutral shadow on hover/active.)
• A gradient is never a colored glow. Depth stays a neutral shadow + top catch-light, never a colored gradient standing in for emission. The accent fill’s lighter top stop and the surfaces’ surface-highlight inset are catch-lights, not neon.
• The faceted field re-tints, it does not tween. Its motion is a per-frame luminance shift on fixed geometry, a static field that breathes, not an animated gradient.

Warning

A colored glow or neon emission is not how Nockerl signals state or depth. See Design laws and Elevation & depth.

Not gradients

For contrast, these are not part of the gradient system and should not be reached for as one:

• Resting cards / panels are flat --color-card-surface1; lift is shadow + catch-light.
• Soft accent fills (secondary/toggle-pressed buttons, selection washes) use a single translucent --color-accent-primary-soft (cyan at ~16%), a flat tint, not a gradient.
• Edge fades (e.g. scroll-overflow masks on Tabs) are a color-to-transparent fade used purely to hint clipped content, not a decorative wash.