/* ============================================
   DESIGN SYSTEM — Ahmed Elkelany Portfolio
   Color tokens, typography, spacing, themes
   ============================================ */

/* Google Fonts */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;500;600&display=swap');

/* ---- CSS Custom Properties ---- */
:root {
  /* Spacing scale (4px base) */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;
  --space-32: 8rem;

  /* Border radius */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.12);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.15);
  --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.2);
  --shadow-xl: 0 16px 50px rgba(0, 0, 0, 0.25);

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;

  /* Font sizes */
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 1.875rem;
  --text-4xl: 2.25rem;
  --text-5xl: 3rem;
  --text-6xl: 3.75rem;
  --text-hero: clamp(2.5rem, 5vw, 4.5rem);

  /* Line heights */
  --leading-tight: 1.15;
  --leading-snug: 1.3;
  --leading-normal: 1.6;
  --leading-relaxed: 1.75;

  /* Font weights */
  --weight-light: 300;
  --weight-regular: 400;
  --weight-medium: 500;
  --weight-semibold: 600;
  --weight-bold: 700;
  --weight-extrabold: 800;

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 400ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-spring: 500ms cubic-bezier(0.34, 1.56, 0.64, 1);

  /* Z-index scale */
  --z-bg: -1;
  --z-base: 1;
  --z-nav: 100;
  --z-modal-backdrop: 200;
  --z-modal: 300;
  --z-entry: 400;
  --z-toast: 500;

  /* Container */
  --container-max: 1200px;
  --container-padding: var(--space-6);

  /* Glass blur */
  --glass-blur: 16px;
  --glass-blur-heavy: 24px;
}

/* ---- DARK THEME (Default) ---- */
[data-theme="dark"] {
  --bg-primary: #0a0e17;
  --bg-secondary: #111827;
  --bg-tertiary: #1e293b;
  --bg-card: rgba(17, 24, 39, 0.65);
  --bg-glass: rgba(17, 24, 39, 0.6);
  --bg-glass-hover: rgba(17, 24, 39, 0.75);
  --bg-glass-strong: rgba(17, 24, 39, 0.85);
  --bg-input: rgba(30, 41, 59, 0.5);

  --accent-primary: #3b82f6;
  --accent-primary-hover: #60a5fa;
  --accent-primary-glow: rgba(59, 130, 246, 0.25);
  --accent-secondary: #06b6d4;
  --accent-secondary-glow: rgba(6, 182, 212, 0.2);
  --accent-tertiary: #8b5cf6;
  --accent-tertiary-glow: rgba(139, 92, 246, 0.2);
  --accent-success: #10b981;
  --accent-warning: #f59e0b;

  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-tertiary: #64748b;
  --text-accent: #60a5fa;
  --text-inverse: #0f172a;

  --border-primary: rgba(148, 163, 184, 0.12);
  --border-hover: rgba(148, 163, 184, 0.25);
  --border-accent: rgba(59, 130, 246, 0.3);

  --glow-primary: rgba(59, 130, 246, 0.15);
  --glow-secondary: rgba(6, 182, 212, 0.1);

  --particle-color: rgba(148, 163, 184, 0.4);
  --grid-color: rgba(148, 163, 184, 0.04);
  --grid-color-strong: rgba(148, 163, 184, 0.08);

  --scrollbar-track: #111827;
  --scrollbar-thumb: #334155;

  color-scheme: dark;
}

/* ---- LIGHT THEME ---- */
[data-theme="light"] {
  --bg-primary: #f0f2f7;
  --bg-secondary: #ffffff;
  --bg-tertiary: #e8ecf3;
  --bg-card: rgba(255, 255, 255, 0.7);
  --bg-glass: rgba(255, 255, 255, 0.65);
  --bg-glass-hover: rgba(255, 255, 255, 0.8);
  --bg-glass-strong: rgba(255, 255, 255, 0.9);
  --bg-input: rgba(241, 245, 249, 0.8);

  --accent-primary: #2563eb;
  --accent-primary-hover: #3b82f6;
  --accent-primary-glow: rgba(37, 99, 235, 0.12);
  --accent-secondary: #0891b2;
  --accent-secondary-glow: rgba(8, 145, 178, 0.1);
  --accent-tertiary: #7c3aed;
  --accent-tertiary-glow: rgba(124, 58, 237, 0.1);
  --accent-success: #059669;
  --accent-warning: #d97706;

  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-tertiary: #94a3b8;
  --text-accent: #2563eb;
  --text-inverse: #f1f5f9;

  --border-primary: rgba(15, 23, 42, 0.08);
  --border-hover: rgba(15, 23, 42, 0.15);
  --border-accent: rgba(37, 99, 235, 0.2);

  --glow-primary: rgba(37, 99, 235, 0.08);
  --glow-secondary: rgba(8, 145, 178, 0.06);

  --particle-color: rgba(71, 85, 105, 0.25);
  --grid-color: rgba(15, 23, 42, 0.03);
  --grid-color-strong: rgba(15, 23, 42, 0.06);

  --scrollbar-track: #e2e8f0;
  --scrollbar-thumb: #94a3b8;

  color-scheme: light;
}

/* ---- GLOBAL RESETS ---- */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  scroll-padding-top: 80px;
}

body {
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  color: var(--text-primary);
  background-color: var(--bg-primary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
  transition: background-color var(--transition-slow), color var(--transition-slow);
}

/* Scrollbar styling */
::-webkit-scrollbar {
  width: 8px;
}
::-webkit-scrollbar-track {
  background: var(--scrollbar-track);
}
::-webkit-scrollbar-thumb {
  background: var(--scrollbar-thumb);
  border-radius: var(--radius-full);
}
::-webkit-scrollbar-thumb:hover {
  background: var(--accent-primary);
}

/* Selection */
::selection {
  background: var(--accent-primary);
  color: #fff;
}

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

/* Images */
img {
  max-width: 100%;
  height: auto;
  display: block;
}

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

/* Focus */
:focus-visible {
  outline: 2px solid var(--accent-primary);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* 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;
  }
}

/* ---- TYPOGRAPHY UTILITIES ---- */
.font-mono {
  font-family: var(--font-mono);
}

.text-gradient {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.text-gradient-alt {
  background: linear-gradient(135deg, var(--accent-secondary), var(--accent-tertiary));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

/* ---- CONTAINER ---- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-padding);
}

/* ---- SECTION BASE ---- */
.section {
  padding: var(--space-24) 0;
  position: relative;
}

.section-header {
  margin-bottom: var(--space-12);
  text-align: center;
}

.section-label {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: var(--weight-medium);
  color: var(--accent-primary);
  text-transform: uppercase;
  letter-spacing: 0.15em;
  margin-bottom: var(--space-3);
  display: block;
}

.section-title {
  font-size: clamp(1.75rem, 3vw, 2.5rem);
  font-weight: var(--weight-bold);
  color: var(--text-primary);
  line-height: var(--leading-tight);
}

.section-subtitle {
  font-size: var(--text-lg);
  color: var(--text-secondary);
  margin-top: var(--space-4);
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

/* ---- SCREEN READER ONLY ---- */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}