```js
// Button.stories.js

import type { Meta, StoryObj } from '@storybook/web-components';

const meta: Meta = {
  title: 'Button',
  component: 'demo-button',
  // 👇 Creates specific argTypes
  argTypes: {
    backgroundColor: { control: 'color' },
  },
  args: {
    // 👇 Now all Button stories will be primary.
    primary: true,
  },
};
export default meta;
```