/* ===================================================
   BASE.CSS — DESIGN TOKENS & CORE SYSTEM
   MD Saib Hossain Portfolio
   Supports Dark (default) and Light Mode via [data-theme]
   =================================================== */

/* ===== DARK THEME (DEFAULT) ===== */
:root,
[data-theme="dark"] {
  color-scheme: dark;

  /* Core Canvas */
  --bg: #090d16;
  --bg-secondary: #0f172a;
  --bg-tertiary: #1e293b;
  --bg-glass: rgba(15, 23, 42, 0.75);
  
  /* Glass Surfaces */
  --surface: rgba(18, 26, 47, 0.7);
  --surface-hover: rgba(30, 41, 69, 0.85);
  --surface-card: rgba(15, 23, 42, 0.65);
  --surface-active: rgba(45, 59, 95, 0.9);
  --surface-input: rgba(15, 23, 42, 0.8);

  /* Primary Brand & Accents */
  --primary: #6366f1;
  --primary-light: #818cf8;
  --primary-dark: #4338ca;
  --primary-glow: rgba(99, 102, 241, 0.35);

  --accent: #06b6d4;
  --accent-light: #22d3ee;
  --accent-dark: #0891b2;
  --accent-glow: rgba(6, 182, 212, 0.35);

  --accent-alt: #10b981;
  --accent-alt-glow: rgba(16, 185, 129, 0.3);

  /* Radiant Gradients */
  --gradient-main: linear-gradient(135deg, #6366f1 0%, #06b6d4 100%);
  --gradient-reverse: linear-gradient(135deg, #06b6d4 0%, #6366f1 100%);
  --gradient-card: linear-gradient(135deg, rgba(255, 255, 255, 0.04) 0%, rgba(255, 255, 255, 0.01) 100%);
  --gradient-glow: radial-gradient(circle, rgba(99, 102, 241, 0.15) 0%, transparent 70%);

  /* Typography */
  --text: #f1f5f9;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --text-faint: #64748b;
  --text-gradient: var(--gradient-main);

  /* Borders & Dividers */
  --border: rgba(255, 255, 255, 0.09);
  --border-light: rgba(255, 255, 255, 0.14);
  --border-hover: rgba(99, 102, 241, 0.45);
  --border-focus: #6366f1;

  /* Shadows & Glows */
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.25);
  --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.35);
  --shadow-lg: 0 20px 45px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 25px var(--primary-glow);

  /* UI Tokens */
  --nav-bg: rgba(9, 13, 22, 0.85);
  --nav-border: rgba(255, 255, 255, 0.08);
  --footer-bg: rgba(7, 10, 18, 0.95);
  --modal-overlay: rgba(3, 7, 18, 0.8);
  --scrollbar-thumb: rgba(99, 102, 241, 0.4);
  --scrollbar-track: #090d16;
  --badge-bg: rgba(99, 102, 241, 0.12);
  --badge-border: rgba(99, 102, 241, 0.25);
  --badge-text: #a5b4fc;
}

/* ===== LIGHT THEME ===== */
[data-theme="light"] {
  color-scheme: light;

  /* Core Canvas */
  --bg: #f8fafc;
  --bg-secondary: #f1f5f9;
  --bg-tertiary: #e2e8f0;
  --bg-glass: rgba(255, 255, 255, 0.88);

  /* Glass Surfaces */
  --surface: rgba(255, 255, 255, 0.9);
  --surface-hover: #f1f5f9;
  --surface-card: #ffffff;
  --surface-active: #e2e8f0;
  --surface-input: #ffffff;

  /* Primary Brand & Accents */
  --primary: #4f46e5;
  --primary-light: #4338ca;
  --primary-dark: #312e81;
  --primary-glow: rgba(79, 70, 229, 0.15);

  --accent: #0284c7;
  --accent-light: #0369a1;
  --accent-dark: #075985;
  --accent-glow: rgba(2, 132, 199, 0.15);

  --accent-alt: #059669;
  --accent-alt-glow: rgba(5, 150, 105, 0.15);

  /* Radiant Gradients */
  --gradient-main: linear-gradient(135deg, #4f46e5 0%, #0284c7 100%);
  --gradient-reverse: linear-gradient(135deg, #0284c7 0%, #4f46e5 100%);
  --gradient-card: linear-gradient(135deg, rgba(79, 70, 229, 0.04) 0%, rgba(2, 132, 199, 0.02) 100%);
  --gradient-glow: radial-gradient(circle, rgba(79, 70, 229, 0.08) 0%, transparent 70%);

  /* Typography */
  --text: #0f172a;
  --text-secondary: #334155;
  --text-muted: #64748b;
  --text-faint: #94a3b8;
  --text-gradient: linear-gradient(135deg, #3730a3 0%, #0369a1 100%);

  /* Borders & Dividers */
  --border: rgba(15, 23, 42, 0.1);
  --border-light: rgba(15, 23, 42, 0.15);
  --border-hover: rgba(79, 70, 229, 0.5);
  --border-focus: #4f46e5;

  /* Shadows & Glows */
  --shadow-sm: 0 2px 8px rgba(15, 23, 42, 0.05);
  --shadow-md: 0 8px 24px rgba(15, 23, 42, 0.08);
  --shadow-lg: 0 20px 45px rgba(15, 23, 42, 0.12);
  --shadow-glow: 0 0 20px rgba(79, 70, 229, 0.15);

  /* UI Tokens */
  --nav-bg: rgba(255, 255, 255, 0.92);
  --nav-border: rgba(15, 23, 42, 0.08);
  --footer-bg: #f8fafc;
  --modal-overlay: rgba(15, 23, 42, 0.65);
  --scrollbar-thumb: rgba(79, 70, 229, 0.35);
  --scrollbar-track: #f1f5f9;
  --badge-bg: rgba(79, 70, 229, 0.09);
  --badge-border: rgba(79, 70, 229, 0.25);
  --badge-text: #3730a3;
}

/* ===== DIMENSIONS & RADII ===== */
:root {
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  --container-max: 1200px;
  --container-padding: 2rem;

  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-smooth: 0.45s cubic-bezier(0.16, 1, 0.3, 1);

  --font-sans: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-heading: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono: 'SF Mono', 'Fira Code', 'Roboto Mono', monospace;
}

@media (max-width: 768px) {
  :root {
    --container-padding: 1.25rem;
  }
}

@media (max-width: 480px) {
  :root {
    --container-padding: 1rem;
  }
}

/* ===== CSS RESET & GLOBAL STYLES ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  background-color: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  line-height: 1.65;
  overflow-x: hidden;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background-color var(--transition-normal), color var(--transition-normal);
}

main {
  flex: 1 0 auto;
}

/* ===== ACCESSIBILITY & FOCUS ===== */
.skip-link {
  position: absolute;
  top: -100px;
  left: 1rem;
  padding: 0.75rem 1.5rem;
  background: var(--primary);
  color: #ffffff;
  z-index: 10000;
  border-radius: var(--radius-md);
  font-weight: 600;
  text-decoration: none;
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: 1rem;
}

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

/* ===== TYPOGRAPHY DEFAULTS ===== */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  color: var(--text);
  line-height: 1.25;
  font-weight: 700;
  letter-spacing: -0.02em;
}

p {
  color: var(--text-secondary);
  line-height: 1.7;
}

a {
  color: inherit;
  text-decoration: none;
  transition: color var(--transition-fast), transform var(--transition-fast);
}

img, svg, picture {
  max-width: 100%;
  height: auto;
  display: block;
}

/* ===== SELECTION & SCROLLBAR ===== */
::selection {
  background: var(--primary);
  color: #ffffff;
}

/* Standard scrollbar-color */
html {
  scrollbar-color: var(--scrollbar-thumb) var(--scrollbar-track);
  scrollbar-width: thin;
}

/* WebKit scrollbar fallback */
@supports not (scrollbar-color: auto) {
  ::-webkit-scrollbar {
    width: 8px;
    height: 8px;
  }

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

  ::-webkit-scrollbar-thumb {
    background: var(--scrollbar-thumb);
    border-radius: 4px;
  }

  ::-webkit-scrollbar-thumb:hover {
    background: var(--primary);
  }
}

/* ===== REDUCED MOTION ===== */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}