CSS-in-JS with Styled Components

# CSS-in-JS with Styled Components for Google Antigravity

Master CSS-in-JS patterns using Styled Components in your Google Antigravity projects. This comprehensive guide covers component styling, theming, and performance optimization for modern React applications.

## Setting Up Styled Components

Configure Styled Components with proper TypeScript support:

```typescript
// src/styles/theme.ts
export const theme = {
  colors: {
    primary: "#6366f1",
    secondary: "#8b5cf6",
    background: "#0a0a0a",
    surface: "#1a1a1a",
    text: "#ffffff",
    textMuted: "#a1a1aa",
    success: "#22c55e",
    warning: "#f59e0b",
    error: "#ef4444",
  },
  spacing: {
    xs: "0.25rem",
    sm: "0.5rem",
    md: "1rem",
    lg: "1.5rem",
    xl: "2rem",
    xxl: "3rem",
  },
  borderRadius: {
    sm: "0.25rem",
    md: "0.5rem",
    lg: "1rem",
    full: "9999px",
  },
  shadows: {
    sm: "0 1px 2px rgba(0, 0, 0, 0.05)",
    md: "0 4px 6px rgba(0, 0, 0, 0.1)",
    lg: "0 10px 15px rgba(0, 0, 0, 0.2)",
  },
  transitions: {
    fast: "150ms ease",
    normal: "300ms ease",
    slow: "500ms ease",
  },
} as const;

export type Theme = typeof theme;
```

## Creating Styled Components

Build reusable styled components with props:

```typescript
// src/components/Button/Button.styled.ts
import styled, { css } from "styled-components";

interface ButtonProps {
  variant?: "primary" | "secondary" | "outline" | "ghost";
  size?: "sm" | "md" | "lg";
  fullWidth?: boolean;
  isLoading?: boolean;
}

const variants = {
  primary: css`
    background: linear-gradient(135deg, ${({ theme }) => theme.colors.primary}, ${({ theme }) => theme.colors.secondary});
    color: white;
    border: none;
    &:hover:not(:disabled) {
      transform: translateY(-2px);
      box-shadow: ${({ theme }) => theme.shadows.lg};
    }
  `,
  secondary: css`
    background: ${({ theme }) => theme.colors.surface};
    color: ${({ theme }) => theme.colors.text};
    border: 1px solid ${({ theme }) => theme.colors.primary};
  `,
  outline: css`
    background: transparent;
    color: ${({ theme }) => theme.colors.primary};
    border: 2px solid ${({ theme }) => theme.colors.primary};
  `,
  ghost: css`
    background: transparent;
    color: ${({ theme }) => theme.colors.text};
    border: none;
    &:hover {
      background: ${({ theme }) => theme.colors.surface};
    }
  `,
};

const sizes = {
  sm: css`
    padding: ${({ theme }) => theme.spacing.xs} ${({ theme }) => theme.spacing.sm};
    font-size: 0.875rem;
  `,
  md: css`
    padding: ${({ theme }) => theme.spacing.sm} ${({ theme }) => theme.spacing.md};
    font-size: 1rem;
  `,
  lg: css`
    padding: ${({ theme }) => theme.spacing.md} ${({ theme }) => theme.spacing.lg};
    font-size: 1.125rem;
  `,
};

export const StyledButton = styled.button<ButtonProps>`
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: ${({ theme }) => theme.spacing.sm};
  border-radius: ${({ theme }) => theme.borderRadius.md};
  font-weight: 600;
  cursor: pointer;
  transition: all ${({ theme }) => theme.transitions.fast};
  width: ${({ fullWidth }) => (fullWidth ? "100%" : "auto")};
  
  ${({ variant = "primary" }) => variants[variant]}
  ${({ size = "md" }) => sizes[size]}
  
  &:disabled {
    opacity: 0.5;
    cursor: not-allowed;
  }
  
  ${({ isLoading }) =>
    isLoading &&
    css`
      pointer-events: none;
      opacity: 0.7;
    `}
`;
```

## Global Styles and Theme Provider

Set up global styles with Antigravity theming:

```typescript
// src/styles/GlobalStyles.ts
import { createGlobalStyle } from "styled-components";

export const GlobalStyles = createGlobalStyle`
  *, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
  }
  
  html {
    font-size: 16px;
    scroll-behavior: smooth;
  }
  
  body {
    font-family: "Inter", -apple-system, sans-serif;
    background: ${({ theme }) => theme.colors.background};
    color: ${({ theme }) => theme.colors.text};
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
  }
  
  a {
    color: ${({ theme }) => theme.colors.primary};
    text-decoration: none;
    transition: color ${({ theme }) => theme.transitions.fast};
    
    &:hover {
      color: ${({ theme }) => theme.colors.secondary};
    }
  }
  
  ::selection {
    background: ${({ theme }) => theme.colors.primary};
    color: white;
  }
`;
```

## Advanced Patterns

Implement polymorphic components and composition:

```typescript
// src/components/Card/Card.styled.ts
import styled from "styled-components";

export const Card = styled.div`
  background: ${({ theme }) => theme.colors.surface};
  border-radius: ${({ theme }) => theme.borderRadius.lg};
  padding: ${({ theme }) => theme.spacing.lg};
  box-shadow: ${({ theme }) => theme.shadows.md};
  transition: all ${({ theme }) => theme.transitions.normal};
  
  &:hover {
    transform: translateY(-4px);
    box-shadow: ${({ theme }) => theme.shadows.lg};
  }
`;

export const CardHeader = styled.div`
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: ${({ theme }) => theme.spacing.md};
  padding-bottom: ${({ theme }) => theme.spacing.md};
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
`;

export const CardTitle = styled.h3`
  font-size: 1.25rem;
  font-weight: 600;
  background: linear-gradient(135deg, ${({ theme }) => theme.colors.primary}, ${({ theme }) => theme.colors.secondary});
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
`;
```

Google Antigravity leverages these patterns to generate consistent, maintainable styling code across your entire application.