/* ============================================
   APP SHELL
   ============================================ */
.app-shell {
  min-height: 100vh;
  position: relative;
}

/* ============================================
   TOP BAR
   ============================================ */
.top-bar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--topbar-height);
  background: var(--bg-topbar);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 var(--space-6);
  z-index: var(--z-topbar);
  transition: background var(--transition-base), border-color var(--transition-base);
}

.top-bar-left {
  display: flex;
  align-items: center;
  gap: var(--space-4);
}

.top-bar-right {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

/* Logo */
.logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  text-decoration: none;
}

.logo-icon {
  width: 36px;
  height: 36px;
  background: var(--gradient-primary);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.125rem;
  flex-shrink: 0;
  box-shadow: 0 4px 12px rgba(99,102,241,0.35);
}

.logo-text {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-bold);
  color: var(--text-primary);
  line-height: 1;
}

.logo-text span {
  color: var(--color-primary);
}

/* Theme Toggle */
.theme-toggle {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  background: var(--bg-input);
  border: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-size: 1.125rem;
  color: var(--text-secondary);
}

.theme-toggle:hover {
  background: var(--bg-card);
  border-color: var(--color-primary);
  color: var(--color-primary);
  transform: scale(1.05);
}

.theme-toggle .icon-sun,
.theme-toggle .icon-moon {
  position: absolute;
  transition: opacity var(--transition-fast), transform var(--transition-fast);
}

[data-theme="light"] .icon-moon { opacity: 1; }
[data-theme="light"] .icon-sun  { opacity: 0; transform: scale(0); }
[data-theme="dark"]  .icon-sun  { opacity: 1; }
[data-theme="dark"]  .icon-moon { opacity: 0; transform: scale(0); }

/* Hamburger */
.hamburger {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  background: var(--bg-input);
  border: 1px solid var(--border-color);
  display: none;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  transition: all var(--transition-fast);
  padding: 0 10px;
}

.hamburger:hover {
  background: var(--bg-card);
  border-color: var(--color-primary);
}

.hamburger span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--text-secondary);
  border-radius: 2px;
  transition: all var(--transition-fast);
}

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

/* ============================================
   SIDEBAR
   ============================================ */
.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: var(--sidebar-width);
  height: 100vh;
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border-color);
  overflow-y: auto;
  overflow-x: hidden;
  z-index: var(--z-sidebar);
  display: flex;
  flex-direction: column;
  transition: transform var(--transition-slow), background var(--transition-base), border-color var(--transition-base);
  padding-top: var(--topbar-height);
}

.sidebar-header {
  padding: var(--space-6) var(--space-4) var(--space-4);
  border-bottom: 1px solid var(--border-color);
}

.sidebar-label {
  font-size: var(--font-size-xs);
  font-weight: var(--font-weight-semibold);
  color: var(--text-muted);
  letter-spacing: var(--letter-spacing-wide);
  text-transform: uppercase;
  padding: var(--space-4) var(--space-4) var(--space-2);
}

/* Nav Links */
.nav-links {
  padding: var(--space-3) var(--space-3);
  flex: 1;
}

.nav-item {
  margin-bottom: var(--space-1);
}

.nav-link {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-lg);
  color: var(--text-secondary);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  text-decoration: none;
  transition: all var(--transition-fast);
  position: relative;
  cursor: pointer;
  white-space: nowrap;
}

.nav-link:hover {
  background: var(--bg-card-hover);
  color: var(--text-primary);
  transform: translateX(3px);
}

.nav-item.active .nav-link {
  background: var(--gradient-primary);
  color: #ffffff;
  box-shadow: 0 4px 15px rgba(99,102,241,0.35);
}

.nav-link-icon {
  font-size: 1.125rem;
  width: 24px;
  text-align: center;
  flex-shrink: 0;
}

.nav-link-text { flex: 1; }

/* Sidebar overlay for mobile */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: var(--bg-overlay);
  z-index: calc(var(--z-sidebar) - 1);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  opacity: 0;
  transition: opacity var(--transition-base);
}

.sidebar-overlay.visible {
  opacity: 1;
}

/* ============================================
   MAIN CONTENT
   ============================================ */
.main-content {
  margin-left: var(--sidebar-width);
  padding-top: var(--topbar-height);
  min-height: 100vh;
  transition: margin-left var(--transition-slow);
}

.content-inner {
  max-width: calc(var(--content-max-width) + var(--space-16));
  margin: 0 auto;
  padding: 0 var(--content-padding);
}

/* ============================================
   SECTION LAYOUT
   ============================================ */
.calculator-section {
  padding: var(--space-12) 0;
  border-bottom: 1px solid var(--border-color);
}

.calculator-section:last-of-type {
  border-bottom: none;
}

.section-header {
  display: flex;
  align-items: flex-start;
  gap: var(--space-4);
  margin-bottom: var(--space-8);
}

.section-icon-wrap {
  width: 56px;
  height: 56px;
  border-radius: var(--radius-xl);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.625rem;
  flex-shrink: 0;
  position: relative;
}

.section-title {
  font-size: var(--font-size-3xl);
  font-weight: var(--font-weight-extrabold);
  letter-spacing: var(--letter-spacing-tight);
  margin-bottom: var(--space-1);
}

.section-subtitle {
  font-size: var(--font-size-base);
  color: var(--text-secondary);
  margin: 0;
}

/* Two-column calculator layout */
.calc-body {
  display: grid;
  grid-template-columns: 420px 1fr;
  gap: var(--space-6);
  align-items: start;
}

/* ============================================
   HERO SECTION
   ============================================ */
.hero-section {
  padding: var(--space-16) 0 var(--space-12);
  position: relative;
  overflow: hidden;
}

.hero-section::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -20%;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(99,102,241,0.08) 0%, transparent 70%);
  pointer-events: none;
}

.hero-section::after {
  content: '';
  position: absolute;
  bottom: -20%;
  left: -10%;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, rgba(6,182,212,0.06) 0%, transparent 70%);
  pointer-events: none;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  background: rgba(99,102,241,0.1);
  border: 1px solid rgba(99,102,241,0.2);
  color: var(--color-primary);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-full);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-6);
  letter-spacing: 0.02em;
}

.hero-title {
  font-size: var(--font-size-6xl);
  font-weight: var(--font-weight-extrabold);
  line-height: 1.1;
  letter-spacing: -0.03em;
  margin-bottom: var(--space-5);
}

.hero-subtitle {
  font-size: var(--font-size-xl);
  color: var(--text-secondary);
  margin-bottom: var(--space-8);
  max-width: 560px;
  line-height: 1.6;
}

.hero-cta {
  display: flex;
  gap: var(--space-4);
  flex-wrap: wrap;
  margin-bottom: var(--space-16);
}

.hero-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-4);
  margin-bottom: var(--space-12);
}

.stat-card {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  text-align: center;
  box-shadow: var(--shadow-card);
  transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.stat-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.stat-value {
  font-size: var(--font-size-4xl);
  font-weight: var(--font-weight-extrabold);
  letter-spacing: var(--letter-spacing-tight);
  line-height: 1;
  margin-bottom: var(--space-2);
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.stat-label {
  font-size: var(--font-size-sm);
  color: var(--text-muted);
  font-weight: var(--font-weight-medium);
}

/* Feature Grid */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-4);
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  padding: var(--space-5) var(--space-6);
  cursor: pointer;
  transition: all var(--transition-base);
  display: flex;
  align-items: center;
  gap: var(--space-4);
  text-decoration: none;
  position: relative;
  overflow: hidden;
  box-shadow: var(--shadow-xs);
}

.feature-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--card-accent, var(--color-primary));
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--transition-base);
}

.feature-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  border-color: var(--card-accent, var(--color-primary));
}

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

.feature-card-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  flex-shrink: 0;
}

.feature-card-text h4 {
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-semibold);
  color: var(--text-primary);
  margin-bottom: 2px;
}

.feature-card-text p {
  font-size: var(--font-size-xs);
  color: var(--text-muted);
  margin: 0;
  line-height: 1.4;
}

/* ============================================
   FOOTER
   ============================================ */
.footer {
  background: var(--bg-card);
  border-top: 1px solid var(--border-color);
  padding: var(--space-8) 0;
  margin-top: var(--space-12);
}

.footer-inner {
  max-width: calc(var(--content-max-width) + var(--space-16));
  margin: 0 auto;
  padding: 0 var(--content-padding);
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-5);
  padding-bottom: var(--space-4);
  border-bottom: 1px solid var(--border-color);
}

.footer-links a {
  font-size: var(--font-size-xs);
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: var(--font-weight-medium);
  transition: color var(--transition-fast);
}

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

.footer-bottom {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-3);
}

.footer-disclaimer {
  font-size: var(--font-size-xs);
  color: var(--text-muted);
  max-width: 700px;
  line-height: 1.6;
}

.footer-copy {
  font-size: var(--font-size-xs);
  color: var(--text-muted);
  white-space: nowrap;
}