/* ================================================
   Arattai.it.com – Main Stylesheet
   Design System: Deep space + electric accent palette
   ================================================ */

/* ---- CSS Variables ---- */
:root {
  /* LIGHT THEME (Default) */
  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --bg-card: #ffffff;
  --bg-card-hover: #f1f5f9;
  --bg-glass: rgba(0,0,0,0.03);
  --bg-glass-hover: rgba(0,0,0,0.06);

  --accent-primary: #7c5cfc;
  --accent: var(--accent-primary);
  --accent-rgb: 124, 92, 252;
  --accent-secondary: #0d9488;
  --accent-tertiary: #d97706;
  --accent-pink: #db2777;

  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #64748b;

  --border-subtle: rgba(0,0,0,0.08);
  --border-active: rgba(124,92,252,0.4);

  --gradient-hero: linear-gradient(135deg, #7c5cfc 0%, #0d9488 100%);
  --gradient-text: linear-gradient(90deg, #7c5cfc 0%, #0d9488 50%, #d97706 100%);
  --gradient-math: linear-gradient(135deg, #6366f1, #818cf8);
  --gradient-time: linear-gradient(135deg, #ec4899, #f9a8d4);
  --gradient-convert: linear-gradient(135deg, #8b5cf6, #c4b5fd);
  --gradient-utility: linear-gradient(135deg, #f59e0b, #fcd34d);
  --gradient-basic: linear-gradient(135deg, #7c5cfc, #a78bfa);
  --gradient-algebra: linear-gradient(135deg, #10b981, #6ee7b7);
  --gradient-geometry: linear-gradient(135deg, #06b6d4, #67e8f9);
  --gradient-trigonometry: linear-gradient(135deg, #e11d48, #fb7185);
  --gradient-calculus: linear-gradient(135deg, #7c3aed, #c4b5fd);

  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --radius-xl: 28px;
  --radius-full: 9999px;

  --shadow-sm: 0 2px 8px rgba(0,0,0,0.05);
  --shadow-md: 0 8px 30px rgba(0,0,0,0.08);
  --shadow-lg: 0 20px 60px rgba(0,0,0,0.12);
  --shadow-glow: 0 0 30px rgba(124,92,252,0.15);

  --nav-h: 70px;
  --transition: 0.3s cubic-bezier(0.4,0,0.2,1);
  --transition-fast: 0.15s ease;
  --transition-bounce: 0.4s cubic-bezier(0.34,1.56,0.64,1);
}

[data-theme='dark'] {
  --bg-primary: #07080f;
  --bg-secondary: #0d0f1c;
  --bg-card: #111424;
  --bg-card-hover: #161a30;
  --bg-glass: rgba(255,255,255,0.04);
  --bg-glass-hover: rgba(255,255,255,0.07);

  --accent-primary: #7c5cfc;
  --accent-secondary: #5eead4;
  --accent-tertiary: #f59e0b;
  --accent-pink: #ec4899;

  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #475569;

  --border-subtle: rgba(255,255,255,0.07);
  --border-active: rgba(124,92,252,0.4);

  --gradient-hero: linear-gradient(135deg, #7c5cfc 0%, #5eead4 100%);
  --gradient-text: linear-gradient(90deg, #a78bfa 0%, #5eead4 50%, #f59e0b 100%);

  --shadow-sm: 0 2px 8px rgba(0,0,0,0.3);
  --shadow-md: 0 8px 30px rgba(0,0,0,0.4);
  --shadow-lg: 0 20px 60px rgba(0,0,0,0.5);
  --shadow-glow: 0 0 30px rgba(124,92,252,0.25);
}

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

html { scroll-behavior: smooth; font-size: 16px; }

body {
  font-family: 'Plus Jakarta Sans', sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
}

a { text-decoration: none; color: inherit; }
img { max-width: 100%; display: block; }
button { cursor: pointer; font-family: inherit; }
ul { list-style: none; }

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

/* ================================================
   NAVBAR
   ================================================ */
.navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--nav-h);
  z-index: 10000;
  transition: var(--transition);
  padding: 0 1rem;
  background: var(--bg-secondary) !important;
  border-bottom: 1px solid var(--border-subtle);
  box-shadow: var(--shadow-md);
}

.navbar.scrolled {
  background: var(--bg-secondary) !important;
  box-shadow: var(--shadow-lg);
}

.nav-container {
  max-width: 1280px;
  margin: 0 auto;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 2rem;
}

/* Logo */
.nav-logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  text-decoration: none;
  flex-shrink: 0;
}

.logo-icon {
  width: 38px; height: 38px;
  background: var(--gradient-hero);
  border-radius: var(--radius-sm);
  display: flex; align-items: center; justify-content: center;
  font-size: 1rem;
  color: #fff;
  box-shadow: 0 0 15px rgba(124,92,252,0.4);
}

.logo-text {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.03em;
}

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

/* Nav Links */
.nav-links {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.theme-toggle {
  background: transparent;
  border: none;
  color: var(--text-primary);
  font-size: 1.1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-full);
  margin-right: 0.5rem;
  transition: var(--transition-fast);
}

.theme-toggle:hover {
  background: var(--bg-glass);
  color: var(--accent-primary);
}

.nav-link {
  padding: 0.5rem 0.9rem;
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  border-radius: var(--radius-sm);
  transition: var(--transition-fast);
}

.nav-link:hover {
  color: var(--text-primary);
  background: var(--bg-glass);
}

/* Categories Dropdown */
.nav-dropdown {
  position: relative;
}

.dropdown-menu {
  position: absolute;
  top: 100%;
  left: 50%;
  transform: translateX(-50%) translateY(10px);
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  box-shadow: var(--shadow-lg);
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 2rem;
  opacity: 0;
  visibility: hidden;
  transition: var(--transition-fast);
  z-index: 1000;
  min-width: 440px;
}

.nav-dropdown:hover .dropdown-menu {
  opacity: 1;
  visibility: visible;
  transform: translateX(-50%) translateY(0);
}

.dropdown-group h4 {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
  padding-bottom: 0.25rem;
  border-bottom: 1px solid var(--border-subtle);
}

.dropdown-group a {
  display: block;
  padding: 0.4rem 0;
  color: var(--text-secondary);
  font-size: 0.85rem;
  text-decoration: none;
  font-weight: 500;
  transition: var(--transition-fast);
}

.dropdown-group a:hover {
  color: var(--accent-primary);
  transform: translateX(3px);
}

.nav-cta {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.5rem 1.2rem;
  background: var(--gradient-hero);
  color: #fff;
  font-size: 0.875rem;
  font-weight: 600;
  border-radius: var(--radius-full);
  margin-left: 0.5rem;
  transition: var(--transition);
  box-shadow: 0 0 20px rgba(124,92,252,0.35);
}

.nav-cta:hover {
  transform: translateY(-1px);
  box-shadow: 0 0 30px rgba(124,92,252,0.5);
}

/* Hamburger */
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  padding: 0.5rem;
  border-radius: var(--radius-sm);
  transition: var(--transition-fast);
}

.nav-toggle:hover { background: var(--bg-glass); }

.nav-toggle span {
  display: block;
  width: 22px; height: 2px;
  background: var(--text-secondary);
  border-radius: var(--radius-full);
  transition: var(--transition);
}

.nav-toggle.active span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle.active span:nth-child(2) { opacity: 0; transform: scaleX(0); }
.nav-toggle.active span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ================================================
   HERO SECTION
   ================================================ */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: calc(var(--nav-h) + 2rem) 1.5rem 5rem;
  overflow: hidden;
}

/* Animated BG */
.hero-bg {
  position: absolute;
  inset: 0;
  pointer-events: none;
}

.hero-blob {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.15;
  animation: blobFloat 8s ease-in-out infinite;
}

.blob-1 {
  width: 600px; height: 600px;
  background: var(--accent-primary);
  top: -200px; left: -150px;
  animation-delay: 0s;
}

.blob-2 {
  width: 500px; height: 500px;
  background: var(--accent-secondary);
  bottom: -100px; right: -100px;
  animation-delay: 3s;
}

.blob-3 {
  width: 350px; height: 350px;
  background: var(--accent-tertiary);
  top: 40%; left: 50%;
  animation-delay: 1.5s;
}

@keyframes blobFloat {
  0%, 100% { transform: translate(0,0) scale(1); }
  33% { transform: translate(30px,-20px) scale(1.05); }
  66% { transform: translate(-20px,15px) scale(0.95); }
}

/* Grid overlay */
.hero-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.03) 1px, transparent 1px);
  background-size: 50px 50px;
  mask-image: radial-gradient(ellipse 80% 60% at 50% 50%, black 40%, transparent 100%);
}

.hero-container {
  position: relative;
  max-width: 800px;
  width: 100%;
  text-align: center;
  z-index: 2;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 1.1rem;
  background: rgba(124,92,252,0.15);
  border: 1px solid rgba(124,92,252,0.3);
  border-radius: var(--radius-full);
  font-size: 0.8rem;
  font-weight: 600;
  color: #a78bfa;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  margin-bottom: 1.5rem;
  animation: fadeInDown 0.7s ease both;
}

.hero-badge i { color: var(--accent-tertiary); font-size: 0.75rem; }

.hero-title {
  font-family: 'Space Grotesk', sans-serif;
  font-size: clamp(2.5rem, 6vw, 4.2rem);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.03em;
  margin-bottom: 1.25rem;
  animation: fadeInDown 0.7s ease 0.1s both;
}

.hero-subtitle {
  font-size: clamp(1rem, 2vw, 1.15rem);
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 2.5rem;
  line-height: 1.7;
  animation: fadeInDown 0.7s ease 0.2s both;
}

/* Hero Search */
.hero-search {
  position: relative;
  max-width: 560px;
  margin: 0 auto 3rem;
  animation: fadeInUp 0.7s ease 0.3s both;
}

.search-wrap {
  display: flex;
  align-items: center;
  gap: 0;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-full);
  padding: 0.4rem 0.4rem 0.4rem 1.2rem;
  transition: var(--transition);
  box-shadow: var(--shadow-md);
}

.search-wrap:focus-within {
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px rgba(124,92,252,0.15), var(--shadow-md);
}

.search-icon {
  color: var(--text-muted);
  font-size: 0.9rem;
  flex-shrink: 0;
  margin-right: 0.6rem;
}

.search-wrap input {
  flex: 1;
  background: none;
  border: none;
  outline: none;
  color: var(--text-primary);
  font-size: 0.95rem;
  font-family: inherit;
  min-width: 0;
}

.search-wrap input::placeholder { color: var(--text-muted); }

.search-btn {
  flex-shrink: 0;
  padding: 0.55rem 1.4rem;
  background: var(--gradient-hero);
  color: #fff;
  font-size: 0.875rem;
  font-weight: 600;
  border: none;
  border-radius: var(--radius-full);
  transition: var(--transition);
  white-space: nowrap;
}

.search-btn:hover { opacity: 0.9; transform: scale(1.02); }

/* Search Suggestions */
.search-suggestions {
  position: absolute;
  top: calc(100% + 8px);
  left: 0; right: 0;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
  z-index: 100;
  display: none;
}

.search-suggestions.show { display: block; }

.suggestion-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 1rem;
  cursor: pointer;
  transition: var(--transition-fast);
  font-size: 0.9rem;
}

.suggestion-item:hover { background: var(--bg-glass-hover); }
.suggestion-item i { color: var(--accent-primary); width: 16px; text-align: center; }

/* Hero Stats */
.hero-stats {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 2rem;
  animation: fadeInUp 0.7s ease 0.4s both;
}

.stat-item {
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.stat-num {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 2rem;
  font-weight: 800;
  background: var(--gradient-text);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1;
}

.stat-plus {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 1.5rem;
  font-weight: 800;
  background: var(--gradient-text);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.stat-label {
  font-size: 0.78rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-top: 0.2rem;
  font-weight: 500;
}

.stat-divider {
  width: 1px; height: 40px;
  background: var(--border-subtle);
}

/* Floating Cards */
.floating-cards {
  position: absolute;
  inset: 0;
  pointer-events: none;
  z-index: 1;
}

.float-card {
  position: absolute;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.6rem 1rem;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-secondary);
  box-shadow: var(--shadow-md);
  animation: floatCard 4s ease-in-out infinite;
  backdrop-filter: blur(10px);
}

.float-card i { font-size: 1rem; }

.fc-1 { top: 20%; left: 5%; animation-delay: 0s; }
.fc-1 i { color: #f59e0b; }
.fc-2 { top: 35%; right: 3%; animation-delay: 1s; }
.fc-2 i { color: #ec4899; }
.fc-3 { bottom: 30%; left: 3%; animation-delay: 2s; }
.fc-3 i { color: #22c55e; }
.fc-4 { bottom: 22%; right: 5%; animation-delay: 0.5s; }
.fc-4 i { color: #ef4444; }

@keyframes floatCard {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

/* ================================================
   MARQUEE STRIP
   ================================================ */
.marquee-strip {
  background: linear-gradient(135deg, rgba(124,92,252,0.12), rgba(94,234,212,0.08));
  border-top: 1px solid var(--border-subtle);
  border-bottom: 1px solid var(--border-subtle);
  padding: 0.9rem 0;
  overflow: hidden;
  white-space: nowrap;
}

.marquee-track {
  display: inline-flex;
  gap: 2.5rem;
  animation: marqueeScroll 35s linear infinite;
}

.marquee-track span {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--text-secondary);
  font-size: 0.83rem;
  font-weight: 500;
  flex-shrink: 0;
}

.marquee-track span i { color: var(--accent-primary); font-size: 0.75rem; }

@keyframes marqueeScroll {
  0% { transform: translateX(0); }
  100% { transform: translateX(-50%); }
}

/* ================================================
   SHARED SECTION STYLES
   ================================================ */
.section-container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 5rem 1.5rem;
}

.section-header {
  text-align: center;
  margin-bottom: 3.5rem;
}

.section-tag {
  display: inline-block;
  padding: 0.35rem 1rem;
  background: rgba(124,92,252,0.12);
  border: 1px solid rgba(124,92,252,0.25);
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  font-weight: 700;
  color: #a78bfa;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 1rem;
}

.section-title {
  font-family: 'Space Grotesk', sans-serif;
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 0.75rem;
  line-height: 1.2;
}

.section-subtitle {
  font-size: 1.05rem;
  color: var(--text-secondary);
  max-width: 560px;
  margin: 0 auto;
  line-height: 1.7;
}

/* ================================================
   CATEGORY CARDS
   ================================================ */
.categories-section {
  background: var(--bg-secondary);
}

.categories-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 1.5rem;
}

.category-card {
  position: relative;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: 1.75rem 1.5rem;
  overflow: hidden;
  transition: var(--transition);
  cursor: pointer;
}

.category-card:hover {
  transform: translateY(-6px);
  border-color: var(--border-active);
  box-shadow: var(--shadow-glow);
  background: var(--bg-card-hover);
}

/* Category glow layer */
.cat-glow {
  position: absolute;
  top: -80px; left: -80px;
  width: 200px; height: 200px;
  border-radius: 50%;
  filter: blur(60px);
  opacity: 0;
  transition: var(--transition);
  pointer-events: none;
}

.category-card:hover .cat-glow { opacity: 0.12; }

.cat-math .cat-glow { background: #6366f1; }
.cat-time .cat-glow { background: #ec4899; }
.cat-convert .cat-glow { background: #8b5cf6; }
.cat-utility .cat-glow { background: #f59e0b; }
.cat-basic .cat-glow { background: #7c5cfc; }
.cat-algebra .cat-glow { background: #10b981; }
.cat-geometry .cat-glow { background: #06b6d4; }
.cat-trigonometry .cat-glow { background: #e11d48; }
.cat-calculus .cat-glow { background: #7c3aed; }

.cat-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  margin-bottom: 1rem;
}

.cat-icon-wrap {
  margin-bottom: 0.25rem;
}

.cat-icon {
  width: 52px; height: 52px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.35rem;
  color: #fff;
  box-shadow: var(--shadow-sm);
}

.cat-math .cat-icon { background: var(--gradient-math); }
.cat-time .cat-icon { background: var(--gradient-time); }
.cat-convert .cat-icon { background: var(--gradient-convert); }
.cat-utility .cat-icon { background: var(--gradient-utility); }
.cat-basic .cat-icon { background: var(--gradient-basic); }
.cat-algebra .cat-icon { background: var(--gradient-algebra); }
.cat-geometry .cat-icon { background: var(--gradient-geometry); }
.cat-trigonometry .cat-icon { background: var(--gradient-trigonometry); }
.cat-calculus .cat-icon { background: var(--gradient-calculus); }

.cat-badge {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  background: var(--bg-glass);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-full);
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--text-muted);
  letter-spacing: 0.05em;
}

.cat-title {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  letter-spacing: -0.02em;
}

.cat-desc {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 1.25rem;
}

.cat-tools {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin-bottom: 1.25rem;
}

.tool-chip {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.3rem 0.7rem;
  background: var(--bg-glass);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-full);
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--text-secondary);
  transition: var(--transition-fast);
}

.tool-chip:hover {
  background: rgba(124,92,252,0.12);
  border-color: rgba(124,92,252,0.3);
  color: var(--text-primary);
}

.tool-chip i { font-size: 0.65rem; color: var(--accent-primary); }

.cat-cta {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--accent-primary);
  transition: var(--transition-fast);
}

.cat-cta i { font-size: 0.75rem; transition: var(--transition-bounce); }
.cat-cta:hover { color: #a78bfa; }
.cat-cta:hover i { transform: translateX(4px); }

/* ================================================
   TOOLS GRID SECTION
   ================================================ */
.tools-section {
  background: var(--bg-primary);
}

/* Filter Tabs */
.filter-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: center;
  margin-bottom: 2.5rem;
}

.filter-btn {
  padding: 0.5rem 1.2rem;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-full);
  color: var(--text-secondary);
  font-size: 0.85rem;
  font-weight: 600;
  transition: var(--transition-fast);
}

.filter-btn:hover {
  background: var(--bg-glass-hover);
  color: var(--text-primary);
}

.filter-btn.active {
  background: var(--accent-primary);
  border-color: var(--accent-primary);
  color: #fff;
  box-shadow: 0 0 20px rgba(124,92,252,0.35);
}

/* Tools Grid */
.tools-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 1.25rem;
}

.tool-card {
  transition: var(--transition);
}

.tool-card.hidden { display: none; }

.tool-card-inner {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  transition: var(--transition);
  height: 100%;
  position: relative;
  overflow: hidden;
  cursor: pointer;
}

.tool-card-inner:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-active);
  transform: translateY(-5px);
  box-shadow: var(--shadow-md);
}

.tool-card-inner::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: var(--gradient-hero);
  transform: scaleX(0);
  transform-origin: left;
  transition: var(--transition);
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
}

.tool-card:hover .tool-card-inner {
  border-color: var(--border-active);
  background: var(--bg-card-hover);
  transform: translateY(-4px);
  box-shadow: var(--shadow-md), 0 0 20px rgba(124,92,252,0.12);
}

.tool-card:hover .tool-card-inner::before { transform: scaleX(1); }

.tool-icon-wrap {
  width: 48px; height: 48px;
  flex-shrink: 0;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, var(--c1), var(--c2));
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  color: #fff;
  box-shadow: 0 4px 12px rgba(0,0,0,0.3);
  transition: var(--transition-bounce);
}

.tool-card:hover .tool-icon-wrap {
  transform: scale(1.08) rotate(-4deg);
}

.tool-info { flex: 1; min-width: 0; }

.tool-category-tag {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-full);
  font-size: 0.68rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 0.4rem;
}

.math-tag { background: rgba(99,102,241,0.15); color: #818cf8; }
.time-tag { background: rgba(236,72,153,0.15); color: #f9a8d4; }
.convert-tag { background: rgba(139,92,246,0.15); color: #c4b5fd; }
.utility-tag { background: rgba(245,158,11,0.15); color: #fcd34d; }
.basic-tag { background: rgba(124,92,252,0.15); color: #a78bfa; }
.algebra-tag { background: rgba(16,185,129,0.15); color: #34d399; }
.geometry-tag { background: rgba(6,182,212,0.15); color: #22d3ee; }

.tool-name {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 0.35rem;
  letter-spacing: -0.02em;
}

.tool-desc {
  font-size: 0.82rem;
  color: var(--text-secondary);
  line-height: 1.55;
  margin-bottom: 0.75rem;
}

.tool-features {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
}

.tool-features span {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  font-size: 0.72rem;
  color: var(--text-muted);
}

.tool-features span i {
  color: var(--accent-secondary);
  font-size: 0.65rem;
}

.tool-launch-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.5rem 0.9rem;
  background: rgba(124,92,252,0.12);
  border: 1px solid rgba(124,92,252,0.2);
  border-radius: var(--radius-sm);
  font-size: 0.78rem;
  font-weight: 700;
  color: #a78bfa;
  white-space: nowrap;
  flex-shrink: 0;
  align-self: center;
  transition: var(--transition-fast);
}

.tool-launch-btn:hover {
  background: rgba(124,92,252,0.2);
  color: #fff;
}

.tool-launch-btn i { font-size: 0.7rem; }

/* No results */
.no-results {
  text-align: center;
  padding: 4rem 2rem;
  color: var(--text-secondary);
}

.no-results i {
  font-size: 3rem;
  color: var(--text-muted);
  margin-bottom: 1rem;
}

.no-results h3 {
  font-size: 1.3rem;
  margin-bottom: 0.5rem;
  color: var(--text-primary);
}

.reset-btn {
  margin-top: 1rem;
  padding: 0.6rem 1.5rem;
  background: var(--accent-primary);
  color: #fff;
  border: none;
  border-radius: var(--radius-full);
  font-size: 0.9rem;
  font-weight: 600;
  transition: var(--transition-fast);
}

.reset-btn:hover { opacity: 0.9; }

/* ================================================
   FEATURES SECTION
   ================================================ */
.features-section {
  background: var(--bg-secondary);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 2rem 1.5rem;
  text-align: center;
  transition: var(--transition);
}

.feature-card:hover {
  transform: translateY(-4px);
  border-color: var(--border-active);
  box-shadow: var(--shadow-glow);
}

.feature-icon {
  width: 58px; height: 58px;
  background: linear-gradient(135deg, rgba(124,92,252,0.2), rgba(94,234,212,0.1));
  border: 1px solid rgba(124,92,252,0.2);
  border-radius: var(--radius-md);
  display: flex; align-items: center; justify-content: center;
  font-size: 1.3rem;
  color: var(--accent-primary);
  margin: 0 auto 1.25rem;
  transition: var(--transition-bounce);
}

.feature-card:hover .feature-icon {
  transform: scale(1.1);
  background: linear-gradient(135deg, rgba(124,92,252,0.3), rgba(94,234,212,0.15));
}

.feature-card h4 {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.feature-card p {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.65;
}

/* ================================================
   CTA SECTION
   ================================================ */
.cta-section {
  position: relative;
  overflow: hidden;
  padding: 5rem 1.5rem;
  text-align: center;
  background: var(--bg-primary);
}

.cta-bg {
  position: absolute;
  inset: 0;
  pointer-events: none;
}

.cta-blob {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.12;
}

.b1 {
  width: 500px; height: 500px;
  background: var(--accent-primary);
  top: -150px; left: -100px;
}

.b2 {
  width: 400px; height: 400px;
  background: var(--accent-secondary);
  bottom: -100px; right: -80px;
}

.cta-container {
  position: relative;
  max-width: 600px;
  margin: 0 auto;
  z-index: 2;
}

.cta-icon-ring {
  width: 70px; height: 70px;
  background: var(--gradient-hero);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.6rem;
  color: #fff;
  margin: 0 auto 1.5rem;
  box-shadow: 0 0 40px rgba(124,92,252,0.45);
  animation: pulse 2.5s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% { box-shadow: 0 0 40px rgba(124,92,252,0.45); }
  50% { box-shadow: 0 0 70px rgba(124,92,252,0.65); }
}

.cta-container h2 {
  font-family: 'Space Grotesk', sans-serif;
  font-size: clamp(1.8rem, 4vw, 2.5rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 1rem;
}

.cta-container p {
  font-size: 1.05rem;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 2rem;
}

.cta-buttons {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

.cta-primary-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.8rem 2rem;
  background: var(--gradient-hero);
  color: #fff;
  font-weight: 700;
  border-radius: var(--radius-full);
  font-size: 0.95rem;
  transition: var(--transition);
  box-shadow: 0 0 30px rgba(124,92,252,0.4);
}

.cta-primary-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 0 45px rgba(124,92,252,0.55);
}

.cta-secondary-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.8rem 2rem;
  background: var(--bg-card);
  color: var(--text-primary);
  font-weight: 700;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-full);
  font-size: 0.95rem;
  transition: var(--transition);
}

.cta-secondary-btn:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-active);
}

/* ================================================
   FAQ SECTION
   ================================================ */
.faq-section {
  background: var(--bg-secondary);
}

.faq-list {
  max-width: 720px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.faq-item {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: var(--transition-fast);
}

.faq-item.open {
  border-color: var(--border-active);
}

.faq-q {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1.2rem 1.5rem;
  background: none;
  border: none;
  color: var(--text-primary);
  font-size: 0.95rem;
  font-weight: 600;
  text-align: left;
  transition: var(--transition-fast);
}

.faq-q:hover { background: var(--bg-glass); }

.faq-icon {
  color: var(--text-muted);
  transition: var(--transition);
  flex-shrink: 0;
  font-size: 0.8rem;
}

.faq-item.open .faq-icon { transform: rotate(180deg); color: var(--accent-primary); }

.faq-a {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.4s cubic-bezier(0.4,0,0.2,1);
}

.faq-item.open .faq-a { max-height: 200px; }

.faq-a p {
  padding: 0 1.5rem 1.2rem;
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ---- Calculator Buttons (Universal) ---- */
.calc-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.6rem;
  width: 100%;
  padding: 1rem 1.5rem;
  background: var(--gradient-hero);
  color: #fff;
  font-size: 1.05rem;
  font-weight: 700;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition);
  margin-top: 1.2rem;
  letter-spacing: 0.02em;
  box-shadow: var(--shadow-sm);
}

.calc-btn:hover {
  opacity: 0.95;
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(124, 92, 252, 0.35);
}

.calc-btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none;
}

/* Page Spacing Utility */
.tool-page {
  padding-top: calc(var(--nav-h) + 2rem);
  min-height: calc(100vh - 400px);
}
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-subtle);
}

.footer-container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 4rem 1.5rem 2rem;
}

.footer-top {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr 1fr;
  gap: 2.5rem;
  margin-bottom: 3rem;
}

.footer-brand p {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.7;
  margin: 1rem 0 1.5rem;
  max-width: 260px;
}

.footer-socials {
  display: flex;
  gap: 0.6rem;
}

.footer-socials a {
  width: 36px; height: 36px;
  background: var(--bg-glass);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  display: flex; align-items: center; justify-content: center;
  color: var(--text-muted);
  font-size: 0.85rem;
  transition: var(--transition-fast);
}

.footer-socials a:hover {
  background: rgba(124,92,252,0.15);
  border-color: rgba(124,92,252,0.3);
  color: var(--accent-primary);
}

.footer-links-group h5 {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-primary);
  margin-bottom: 1rem;
}

.footer-links-group ul {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.footer-links-group a {
  font-size: 0.875rem;
  color: var(--text-secondary);
  transition: var(--transition-fast);
}

.footer-links-group a:hover {
  color: var(--accent-primary);
  padding-left: 4px;
}

.footer-bottom {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-subtle);
  font-size: 0.82rem;
  color: var(--text-muted);
}

.footer-bottom-links {
  display: flex;
  gap: 1.5rem;
}

.footer-bottom-links a {
  color: var(--text-muted);
  transition: var(--transition-fast);
}

.footer-bottom-links a:hover { color: var(--text-primary); }

/* ================================================
   BACK TO TOP
   ================================================ */
.back-to-top {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  width: 44px; height: 44px;
  background: var(--gradient-hero);
  color: #fff;
  border: none;
  border-radius: var(--radius-md);
  font-size: 0.9rem;
  display: flex; align-items: center; justify-content: center;
  box-shadow: 0 0 20px rgba(124,92,252,0.4);
  cursor: pointer;
  transition: var(--transition);
  opacity: 0;
  transform: translateY(10px);
  pointer-events: none;
  z-index: 900;
}

.back-to-top.visible {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}

.back-to-top:hover {
  transform: translateY(-3px);
  box-shadow: 0 0 30px rgba(124,92,252,0.6);
}

/* ================================================
   ANIMATIONS
   ================================================ */
@keyframes fadeInDown {
  from { opacity: 0; transform: translateY(-20px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Intersection observer reveal */
.reveal {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Stagger delay helpers */
.delay-1 { transition-delay: 0.1s; }
.delay-2 { transition-delay: 0.2s; }
.delay-3 { transition-delay: 0.3s; }
.delay-4 { transition-delay: 0.4s; }

/* ================================================
   RESPONSIVE DESIGN
   ================================================ */

/* Large Desktop */
@media (min-width: 1400px) {
  .categories-grid { grid-template-columns: repeat(4, 1fr); }
}

/* Tablet landscape */
@media (max-width: 1200px) {
  .categories-grid { grid-template-columns: repeat(2, 1fr); }
  .footer-top { grid-template-columns: 1fr 1fr 1fr; }
  .footer-brand { grid-column: 1 / -1; }
  .features-grid { grid-template-columns: repeat(3, 1fr); }
}

/* Tablet */
@media (max-width: 900px) {
  :root { --nav-h: 62px; }

  .nav-links { display: none; }

  .nav-links.open {
    display: flex;
    flex-direction: column;
    position: fixed;
    top: var(--nav-h);
    left: 0; right: 0;
    background: var(--bg-secondary);
    backdrop-filter: none;
    padding: 1.5rem;
    gap: 0.5rem;
    border-bottom: 1px solid var(--border-subtle);
    z-index: 999;
    animation: slideDown 0.3s ease;
    overflow-y: auto;
    max-height: calc(100vh - var(--nav-h));
  }

  @keyframes slideDown {
    from { opacity: 0; transform: translateY(-10px); }
    to { opacity: 1; transform: translateY(0); }
  }

  .nav-links.open .nav-link { padding: 0.75rem 1rem; border-radius: var(--radius-sm); width: 100%; text-align: left; }
  .nav-links.open .nav-cta { align-self: flex-start; margin-left: 0; margin-top: 0.5rem; }

  .dropdown-menu {
    position: static;
    transform: none;
    box-shadow: none;
    border: none;
    background: var(--bg-secondary);
    min-width: 100%;
    grid-template-columns: 1fr;
    display: none;
    padding: 0.5rem 1rem;
    gap: 1rem;
  }
  .dropdown-menu.show { display: grid; }

  .nav-toggle { display: flex; }

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

  .float-card { display: none; }

  .footer-top { grid-template-columns: 1fr 1fr; }
  .footer-brand { grid-column: 1 / -1; }
}

/* Mobile */
@media (max-width: 640px) {
  .hero { padding-bottom: 4rem; }

  .hero-stats {
    gap: 1.25rem;
  }

  .stat-num { font-size: 1.6rem; }

  .categories-grid { grid-template-columns: 1fr; }

  .tools-grid { grid-template-columns: 1fr; }

  .features-grid { grid-template-columns: 1fr; }

  .filter-tabs { gap: 0.4rem; }
  .filter-btn { padding: 0.45rem 0.9rem; font-size: 0.78rem; }

  .footer-top { grid-template-columns: 1fr; gap: 2rem; }
  .footer-bottom { flex-direction: column; text-align: center; }
  .footer-bottom-links { justify-content: center; }

  .cta-buttons { flex-direction: column; align-items: center; }
  .cta-primary-btn, .cta-secondary-btn { width: 100%; max-width: 280px; justify-content: center; }

  .section-container { padding: 4rem 1rem; }

  .tool-card-inner { flex-wrap: wrap; }
  .tool-launch-btn { align-self: flex-start; margin-top: 0.5rem; }
}

/* Very small mobile */
@media (max-width: 380px) {
  .hero-title { font-size: 2rem; }
  .hero-badge { font-size: 0.7rem; }
  .search-wrap input { font-size: 0.85rem; }
  .search-btn { padding: 0.5rem 0.9rem; font-size: 0.78rem; }
}

/* ================================================
   CUSTOM SCROLLBAR
   ================================================ */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg-primary); }
::-webkit-scrollbar-thumb {
  background: var(--accent-primary);
  border-radius: var(--radius-full);
  opacity: 0.5;
}
::-webkit-scrollbar-thumb:hover { opacity: 1; }

/* ================================================
   SELECTION
   ================================================ */
::selection {
  background: rgba(124,92,252,0.35);
  color: var(--text-primary);
}

/* ================================================
   TOOL PAGE SHARED STYLES
   ================================================ */
.tool-page {
  padding: calc(var(--nav-h) + 2rem) 1.5rem 4rem;
  max-width: 900px;
  margin: 0 auto;
}
.tool-page-header {
  text-align: center;
  margin-bottom: 2.5rem;
}
.tool-page-header h1 {
  font-family: 'Space Grotesk', sans-serif;
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 800;
  margin-bottom: 0.75rem;
}
.tool-page-header p {
  color: var(--text-secondary);
  font-size: 1.05rem;
}
.article-section {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: 2.5rem;
}
.article-section h2 {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 1.6rem;
  font-weight: 700;
  margin-bottom: 1rem;
  margin-top: 1.75rem;
}
.article-section h2:first-child {
  margin-top: 0;
}
.article-section p {
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 1rem;
}
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-bottom: 1.5rem;
}
.breadcrumb a {
  color: var(--text-secondary);
  transition: var(--transition-fast);
}
.breadcrumb a:hover {
  color: var(--accent-primary);
}
.breadcrumb i {
  font-size: 0.6rem;
}