/* ==========================================================================
   TechBlog — Design System Foundation (index.css)
   ==========================================================================
   This file establishes the design tokens, CSS reset, base typography,
   theme support, and utility classes used across the entire application.
   ========================================================================== */

/* --------------------------------------------------------------------------
   Google Fonts
   -------------------------------------------------------------------------- */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=JetBrains+Mono:wght@400&display=swap');

/* --------------------------------------------------------------------------
   CSS Custom Properties — Design Tokens
   -------------------------------------------------------------------------- */
:root {
  /* — Colors: Backgrounds — */
  --color-bg-primary: #0a0f1e;
  --color-bg-secondary: #111827;
  --color-bg-card: rgba(255, 255, 255, 0.05);
  --color-bg-card-hover: rgba(255, 255, 255, 0.08);
  --color-bg-elevated: rgba(255, 255, 255, 0.07);
  --color-bg-input: rgba(255, 255, 255, 0.06);
  --color-bg-code: rgba(255, 255, 255, 0.08);
  --color-bg-overlay: rgba(10, 15, 30, 0.8);

  /* — Colors: Text — */
  --color-text-primary: #e2e8f0;
  --color-text-secondary: #94a3b8;
  --color-text-tertiary: #64748b;
  --color-text-inverse: #0f172a;
  --color-text-link: #3b82f6;

  /* — Colors: Accent — */
  --color-accent-primary: #3b82f6;
  --color-accent-secondary: #06b6d4;
  --color-accent-tertiary: #8b5cf6;
  --color-accent-success: #22c55e;
  --color-accent-warning: #f59e0b;
  --color-accent-danger: #ef4444;

  /* — Colors: Borders — */
  --color-border: rgba(255, 255, 255, 0.08);
  --color-border-hover: rgba(255, 255, 255, 0.15);
  --color-border-focus: var(--color-accent-primary);

  /* — Gradients — */
  --gradient-primary: linear-gradient(135deg, #3b82f6, #8b5cf6);
  --gradient-secondary: linear-gradient(135deg, #06b6d4, #3b82f6);
  --gradient-accent: linear-gradient(135deg, #8b5cf6, #ec4899);
  --gradient-hero: linear-gradient(180deg, rgba(10, 15, 30, 0) 0%, rgba(10, 15, 30, 0.85) 100%);
  --gradient-text: linear-gradient(135deg, #3b82f6, #8b5cf6);
  --gradient-border: linear-gradient(135deg, #3b82f6, #8b5cf6, #06b6d4);

  /* — Spacing Scale — */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 24px;
  --space-6: 32px;
  --space-7: 48px;
  --space-8: 64px;

  /* — Font Families — */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', 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-regular: 400;
  --font-medium: 500;
  --font-semibold: 600;
  --font-bold: 700;

  /* — Line Heights — */
  --leading-tight: 1.25;
  --leading-snug: 1.375;
  --leading-normal: 1.5;
  --leading-relaxed: 1.625;
  --leading-loose: 2;

  /* — Border Radius — */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;
  --radius-2xl: 24px;
  --radius-full: 9999px;

  /* — Shadows — */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -4px rgba(0, 0, 0, 0.3);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.5), 0 8px 10px -6px rgba(0, 0, 0, 0.4);
  --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.6);
  --shadow-glow-blue: 0 0 20px rgba(59, 130, 246, 0.3);
  --shadow-glow-purple: 0 0 20px rgba(139, 92, 246, 0.3);
  --shadow-glow-cyan: 0 0 20px rgba(6, 182, 212, 0.3);

  /* — Transitions — */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 350ms ease;
  --transition-spring: 500ms cubic-bezier(0.34, 1.56, 0.64, 1);

  /* — Z-Index Scale — */
  --z-base: 1;
  --z-dropdown: 100;
  --z-sticky: 500;
  --z-navbar: 1000;
  --z-modal: 2000;
  --z-tooltip: 3000;

  /* — Backdrop Filters — */
  --blur-sm: blur(4px);
  --blur-md: blur(12px);
  --blur-lg: blur(24px);
}

/* --------------------------------------------------------------------------
   Light Theme Overrides
   -------------------------------------------------------------------------- */
[data-theme="light"] {
  --color-bg-primary: #f8fafc;
  --color-bg-secondary: #f1f5f9;
  --color-bg-card: rgba(255, 255, 255, 0.8);
  --color-bg-card-hover: rgba(255, 255, 255, 0.95);
  --color-bg-elevated: rgba(255, 255, 255, 0.9);
  --color-bg-input: rgba(0, 0, 0, 0.04);
  --color-bg-code: rgba(0, 0, 0, 0.05);
  --color-bg-overlay: rgba(248, 250, 252, 0.8);

  --color-text-primary: #0f172a;
  --color-text-secondary: #475569;
  --color-text-tertiary: #94a3b8;
  --color-text-inverse: #f8fafc;
  --color-text-link: #2563eb;

  --color-border: rgba(0, 0, 0, 0.08);
  --color-border-hover: rgba(0, 0, 0, 0.15);

  --gradient-hero: linear-gradient(180deg, rgba(248, 250, 252, 0) 0%, rgba(248, 250, 252, 0.85) 100%);

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.08), 0 2px 4px -2px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.06);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.08);
  --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.15);
  --shadow-glow-blue: 0 0 20px rgba(59, 130, 246, 0.15);
  --shadow-glow-purple: 0 0 20px rgba(139, 92, 246, 0.15);
  --shadow-glow-cyan: 0 0 20px rgba(6, 182, 212, 0.15);
}

/* --------------------------------------------------------------------------
   Modern CSS Reset
   -------------------------------------------------------------------------- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
  -moz-text-size-adjust: 100%;
  text-size-adjust: 100%;
  font-size: 16px;
  line-height: var(--leading-normal);
  tab-size: 4;
}

body {
  font-family: var(--font-sans);
  font-size: var(--text-base);
  font-weight: var(--font-regular);
  line-height: var(--leading-normal);
  color: var(--color-text-primary);
  background-color: var(--color-bg-primary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  min-height: 100vh;
  overflow-x: hidden;
}

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

input,
button,
textarea,
select {
  font: inherit;
  color: inherit;
}

a {
  color: inherit;
  text-decoration: none;
}

ul,
ol {
  list-style: none;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-sans);
  font-weight: var(--font-bold);
  line-height: var(--leading-tight);
  overflow-wrap: break-word;
}

p {
  overflow-wrap: break-word;
}

button {
  cursor: pointer;
  background: none;
  border: none;
}

table {
  border-collapse: collapse;
  border-spacing: 0;
}

/* --------------------------------------------------------------------------
   Selection Styling
   -------------------------------------------------------------------------- */
::selection {
  background-color: rgba(59, 130, 246, 0.3);
  color: var(--color-text-primary);
}

::-moz-selection {
  background-color: rgba(59, 130, 246, 0.3);
  color: var(--color-text-primary);
}

/* --------------------------------------------------------------------------
   Scrollbar Styling
   -------------------------------------------------------------------------- */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--color-bg-primary);
}

::-webkit-scrollbar-thumb {
  background: var(--color-border);
  border-radius: var(--radius-full);
  border: 2px solid var(--color-bg-primary);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--color-text-tertiary);
}

/* Firefox scrollbar */
* {
  scrollbar-width: thin;
  scrollbar-color: var(--color-border) var(--color-bg-primary);
}

/* --------------------------------------------------------------------------
   Focus Visible — Accessible Focus Rings
   -------------------------------------------------------------------------- */
:focus-visible {
  outline: 2px solid var(--color-accent-primary);
  outline-offset: 2px;
}

:focus:not(:focus-visible) {
  outline: none;
}

/* --------------------------------------------------------------------------
   Utility Classes — Text Colors
   -------------------------------------------------------------------------- */
.text-primary   { color: var(--color-text-primary); }
.text-secondary { color: var(--color-text-secondary); }
.text-tertiary  { color: var(--color-text-tertiary); }
.text-accent    { color: var(--color-accent-primary); }
.text-cyan      { color: var(--color-accent-secondary); }
.text-purple    { color: var(--color-accent-tertiary); }
.text-success   { color: var(--color-accent-success); }
.text-warning   { color: var(--color-accent-warning); }
.text-danger    { color: var(--color-accent-danger); }

.text-gradient {
  background: var(--gradient-text);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

/* --------------------------------------------------------------------------
   Utility Classes — Backgrounds
   -------------------------------------------------------------------------- */
.bg-primary   { background-color: var(--color-bg-primary); }
.bg-secondary { background-color: var(--color-bg-secondary); }
.bg-card      { background-color: var(--color-bg-card); }
.bg-elevated  { background-color: var(--color-bg-elevated); }
.bg-gradient  { background: var(--gradient-primary); }

/* --------------------------------------------------------------------------
   Utility Classes — Typography
   -------------------------------------------------------------------------- */
.font-sans { font-family: var(--font-sans); }
.font-mono { font-family: var(--font-mono); }

.text-xs   { font-size: var(--text-xs); }
.text-sm   { font-size: var(--text-sm); }
.text-base { font-size: var(--text-base); }
.text-lg   { font-size: var(--text-lg); }
.text-xl   { font-size: var(--text-xl); }
.text-2xl  { font-size: var(--text-2xl); }
.text-3xl  { font-size: var(--text-3xl); }
.text-4xl  { font-size: var(--text-4xl); }
.text-5xl  { font-size: var(--text-5xl); }

.font-regular  { font-weight: var(--font-regular); }
.font-medium   { font-weight: var(--font-medium); }
.font-semibold { font-weight: var(--font-semibold); }
.font-bold     { font-weight: var(--font-bold); }

.text-center { text-align: center; }
.text-left   { text-align: left; }
.text-right  { text-align: right; }

.uppercase   { text-transform: uppercase; }
.capitalize  { text-transform: capitalize; }
.truncate {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.line-clamp-2 {
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.line-clamp-3 {
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

/* --------------------------------------------------------------------------
   Utility Classes — Flexbox
   -------------------------------------------------------------------------- */
.flex        { display: flex; }
.inline-flex { display: inline-flex; }

.flex-row    { flex-direction: row; }
.flex-col    { flex-direction: column; }
.flex-wrap   { flex-wrap: wrap; }

.items-start   { align-items: flex-start; }
.items-center  { align-items: center; }
.items-end     { align-items: flex-end; }
.items-stretch { align-items: stretch; }

.justify-start   { justify-content: flex-start; }
.justify-center  { justify-content: center; }
.justify-end     { justify-content: flex-end; }
.justify-between { justify-content: space-between; }
.justify-around  { justify-content: space-around; }

.flex-1    { flex: 1 1 0%; }
.flex-auto { flex: 1 1 auto; }
.flex-none { flex: none; }

.gap-1 { gap: var(--space-1); }
.gap-2 { gap: var(--space-2); }
.gap-3 { gap: var(--space-3); }
.gap-4 { gap: var(--space-4); }
.gap-5 { gap: var(--space-5); }
.gap-6 { gap: var(--space-6); }
.gap-7 { gap: var(--space-7); }
.gap-8 { gap: var(--space-8); }

/* --------------------------------------------------------------------------
   Utility Classes — Grid Helpers
   -------------------------------------------------------------------------- */
.grid { display: grid; }

.grid-cols-1 { grid-template-columns: repeat(1, 1fr); }
.grid-cols-2 { grid-template-columns: repeat(2, 1fr); }
.grid-cols-3 { grid-template-columns: repeat(3, 1fr); }
.grid-cols-4 { grid-template-columns: repeat(4, 1fr); }

.col-span-2 { grid-column: span 2; }
.col-span-3 { grid-column: span 3; }
.col-span-full { grid-column: 1 / -1; }

/* --------------------------------------------------------------------------
   Utility Classes — Spacing
   -------------------------------------------------------------------------- */
.m-0  { margin: 0; }
.mt-1 { margin-top: var(--space-1); }
.mt-2 { margin-top: var(--space-2); }
.mt-3 { margin-top: var(--space-3); }
.mt-4 { margin-top: var(--space-4); }
.mt-5 { margin-top: var(--space-5); }
.mt-6 { margin-top: var(--space-6); }
.mt-7 { margin-top: var(--space-7); }
.mt-8 { margin-top: var(--space-8); }

.mb-1 { margin-bottom: var(--space-1); }
.mb-2 { margin-bottom: var(--space-2); }
.mb-3 { margin-bottom: var(--space-3); }
.mb-4 { margin-bottom: var(--space-4); }
.mb-5 { margin-bottom: var(--space-5); }
.mb-6 { margin-bottom: var(--space-6); }
.mb-7 { margin-bottom: var(--space-7); }
.mb-8 { margin-bottom: var(--space-8); }

.p-1 { padding: var(--space-1); }
.p-2 { padding: var(--space-2); }
.p-3 { padding: var(--space-3); }
.p-4 { padding: var(--space-4); }
.p-5 { padding: var(--space-5); }
.p-6 { padding: var(--space-6); }
.p-7 { padding: var(--space-7); }
.p-8 { padding: var(--space-8); }

/* --------------------------------------------------------------------------
   Utility Classes — Misc
   -------------------------------------------------------------------------- */
.rounded-sm   { border-radius: var(--radius-sm); }
.rounded-md   { border-radius: var(--radius-md); }
.rounded-lg   { border-radius: var(--radius-lg); }
.rounded-xl   { border-radius: var(--radius-xl); }
.rounded-2xl  { border-radius: var(--radius-2xl); }
.rounded-full { border-radius: var(--radius-full); }

.shadow-sm  { box-shadow: var(--shadow-sm); }
.shadow-md  { box-shadow: var(--shadow-md); }
.shadow-lg  { box-shadow: var(--shadow-lg); }
.shadow-xl  { box-shadow: var(--shadow-xl); }
.shadow-2xl { box-shadow: var(--shadow-2xl); }

.relative { position: relative; }
.absolute { position: absolute; }
.fixed    { position: fixed; }
.sticky   { position: sticky; }

.overflow-hidden { overflow: hidden; }
.overflow-auto   { overflow: auto; }

.w-full { width: 100%; }
.h-full { height: 100%; }

.opacity-0   { opacity: 0; }
.opacity-50  { opacity: 0.5; }
.opacity-100 { opacity: 1; }

.pointer-events-none { pointer-events: none; }

.transition-fast { transition: all var(--transition-fast); }
.transition-base { transition: all var(--transition-base); }
.transition-slow { transition: all var(--transition-slow); }