The system's container. Paper for content on light pages, dark for cards sitting on an ink page, ink for hero/feature blocks (carries the radial glow), gradient for the one payoff moment per view.

```jsx
<Card variant="paper">Karte hell</Card>
<Card variant="ink"><Eyebrow tone="lilac">Feature</Eyebrow></Card>
<Card variant="gradient">Dein System</Card>
```

Never stack a gradient card inside a gradient surface; depth comes from the glow, not from shadows.