/* ========================================
   CSS Variables (Design Tokens)
   ======================================== */
:root {
    /* Colors */
    --color-primary: #3b82f6;
    --color-primary-dark: #2563eb;
    --color-success: #10b981;
    --color-warning: #f59e0b;
    --color-caution: #f97316;
    --color-danger: #ef4444;

    /* Grays */
    --color-gray-50: #f9fafb;
    --color-gray-100: #f3f4f6;
    --color-gray-200: #e5e7eb;
    --color-gray-300: #d1d5db;
    --color-gray-400: #9ca3af;
    --color-gray-500: #6b7280;
    --color-gray-600: #4b5563;
    --color-gray-700: #374151;
    --color-gray-800: #1f2937;
    --color-gray-900: #111827;

    /* Semantic colors */
    --color-text: var(--color-gray-900);
    --color-text-muted: var(--color-gray-600);
    --color-background: #ffffff;
    --color-background-alt: var(--color-gray-50);
    --color-border: var(--color-gray-200);

    /* Spacing scale */
    --space-1: 4px;
    --space-2: 8px;
    --space-3: 12px;
    --space-4: 16px;
    --space-5: 20px;
    --space-6: 24px;
    --space-8: 32px;
    --space-10: 40px;
    --space-12: 48px;
    --space-16: 64px;
    --space-20: 80px;
    --space-24: 96px;

    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-mono: "JetBrains Mono", "Fira Code", "SF Mono", Monaco, Consolas, "Liberation Mono", "Courier New", monospace;

    /* Font sizes */
    --text-xs: 0.75rem;      /* 12px */
    --text-sm: 0.875rem;     /* 14px */
    --text-base: 1rem;       /* 16px */
    --text-lg: 1.125rem;     /* 18px */
    --text-xl: 1.25rem;      /* 20px */
    --text-2xl: 1.5rem;      /* 24px */
    --text-3xl: 1.875rem;    /* 30px */
    --text-4xl: 2.25rem;     /* 36px */
    --text-5xl: 3rem;        /* 48px */

    /* Font weights */
    --font-normal: 400;
    --font-medium: 500;
    --font-semibold: 600;
    --font-bold: 700;

    /* Line heights */
    --leading-tight: 1.25;
    --leading-normal: 1.5;
    --leading-relaxed: 1.75;

    /* Border radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-full: 9999px;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);

    /* Layout */
    --container-max-width: 1200px;
    --breakpoint-sm: 640px;
    --breakpoint-md: 768px;
    --breakpoint-lg: 1024px;

    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 250ms ease-in-out;
    --transition-slow: 350ms ease-in-out;
}

/* ========================================
   CSS Reset / Normalize
   ======================================== */

/* Box sizing */
*,
*::before,
*::after {
    box-sizing: border-box;
}

/* Reset margins and paddings */
* {
    margin: 0;
    padding: 0;
}

/* HTML & Body */
html {
    -webkit-text-size-adjust: 100%;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-sans);
    font-size: var(--text-base);
    line-height: var(--leading-normal);
    color: var(--color-text);
    background-color: var(--color-background);
    min-height: 100vh;
}

/* Lists */
ul,
ol {
    list-style: none;
}

/* Links */
a {
    color: var(--color-primary);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--color-primary-dark);
    text-decoration: underline;
}

a:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
    border-radius: var(--radius-sm);
}

/* Buttons */
button {
    font-family: inherit;
    font-size: inherit;
    line-height: inherit;
    cursor: pointer;
    border: none;
    background: none;
}

button:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* Forms */
input,
textarea,
select {
    font-family: inherit;
    font-size: inherit;
    line-height: inherit;
}

/* Images */
img,
picture,
video,
canvas,
svg {
    display: block;
    max-width: 100%;
}

/* ========================================
   Typography
   ======================================== */

h1, h2, h3, h4, h5, h6 {
    font-weight: var(--font-bold);
    line-height: var(--leading-tight);
    margin-bottom: var(--space-4);
    color: var(--color-text);
}

h1 {
    font-size: var(--text-4xl);
}

h2 {
    font-size: var(--text-3xl);
}

h3 {
    font-size: var(--text-2xl);
}

h4 {
    font-size: var(--text-xl);
}

h5 {
    font-size: var(--text-lg);
}

h6 {
    font-size: var(--text-base);
}

p {
    margin-bottom: var(--space-4);
}

p:last-child {
    margin-bottom: 0;
}

/* Code */
code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    background-color: var(--color-gray-100);
    padding: var(--space-1) var(--space-2);
    border-radius: var(--radius-sm);
    color: var(--color-gray-800);
}

pre {
    font-family: var(--font-mono);
    font-size: var(--text-sm);
    background-color: var(--color-gray-900);
    color: var(--color-gray-100);
    padding: var(--space-4);
    border-radius: var(--radius-md);
    overflow-x: auto;
    margin-bottom: var(--space-6);
}

pre code {
    background: none;
    padding: 0;
    color: inherit;
    font-size: inherit;
}

/* Strong & Em */
strong {
    font-weight: var(--font-bold);
}

em {
    font-style: italic;
}

/* ========================================
   Utility Classes
   ======================================== */

.container {
    width: 100%;
    max-width: var(--container-max-width);
    margin-left: auto;
    margin-right: auto;
    padding-left: var(--space-4);
    padding-right: var(--space-4);
}

@media (min-width: 768px) {
    .container {
        padding-left: var(--space-6);
        padding-right: var(--space-6);
    }
}

/* Visually hidden (for accessibility) */
.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

/* Screen reader only */
.sr-only {
    position: absolute;
    left: -10000px;
    width: 1px;
    height: 1px;
    overflow: hidden;
}