/* Reset & Base */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  color: #1e293b;
  background: #f0f7ff;
  line-height: 1.6;
  min-width: 320px;
}
a { color: #2563eb; text-decoration: none; }
a:hover { text-decoration: underline; }
img { max-width: 100%; display: block; }
ul { list-style: none; }
h1, h2, h3, h4 { line-height: 1.3; }
h1 { font-size: 2rem; }
h2 { font-size: 1.5rem; }
h3 { font-size: 1.25rem; }

/* Container */
.container { max-width: 1100px; margin: 0 auto; padding: 0 1rem; }

/* Header / Nav */
.header {
  background: #fff;
  border-bottom: 1px solid #e2e8f0;
  position: sticky;
  top: 0;
  z-index: 100;
}
.nav { display: flex; align-items: center; justify-content: space-between; padding: .75rem 1rem; max-width: 1100px; margin: 0 auto; }
.nav-logo { font-weight: 700; font-size: 1.15rem; color: #2563eb; }
.nav-links { display: flex; gap: 1.25rem; align-items: center; }
.nav-links a { color: #475569; font-size: .95rem; }
.nav-links a:hover { color: #2563eb; text-decoration: none; }
.nav-toggle { display: none; background: none; border: none; font-size: 1.5rem; cursor: pointer; color: #1e293b; }

/* Tools dropdown */
.dropdown { position: relative; }
.dropdown-toggle { cursor: pointer; color: #475569; font-size: .95rem; background: none; border: none; font-family: inherit; display: flex; align-items: center; gap: .25rem; }
.dropdown-toggle:hover { color: #2563eb; }
.dropdown-toggle::after { content: '▾'; font-size: .75rem; }
.dropdown-menu {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  background: #fff;
  border: 1px solid #e2e8f0;
  border-radius: 8px;
  box-shadow: 0 4px 12px rgba(0,0,0,.1);
  min-width: 220px;
  padding: .5rem 0;
  z-index: 200;
}
.dropdown-menu a { display: block; padding: .5rem 1rem; color: #475569; font-size: .9rem; }
.dropdown-menu a:hover { background: #f0f7ff; color: #2563eb; text-decoration: none; }
.dropdown:hover .dropdown-menu { display: block; }
.dropdown-menu.show { display: block; }

@media (max-width: 768px) {
  .nav-toggle { display: block; }
  .nav-links {
    display: none;
    flex-direction: column;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: #fff;
    border-bottom: 1px solid #e2e8f0;
    padding: 1rem;
    gap: .75rem;
  }
  .nav-links.active { display: flex; }
  .dropdown-menu { position: static; box-shadow: none; border: none; padding-left: 1rem; }
  .dropdown:hover .dropdown-menu { display: none; }
  .dropdown-menu.show { display: block; }
}

/* Hero */
.hero {
  background: linear-gradient(135deg, #2563eb 0%, #1d4ed8 100%);
  color: #fff;
  padding: 3rem 1rem;
  text-align: center;
}
.hero h1 { font-size: 2.25rem; margin-bottom: .75rem; }
.hero p { font-size: 1.1rem; opacity: .9; max-width: 600px; margin: 0 auto; }

/* Buttons */
.btn {
  display: inline-block;
  padding: .65rem 1.5rem;
  border-radius: 8px;
  font-weight: 600;
  font-size: .95rem;
  border: none;
  cursor: pointer;
  transition: background .2s;
}
.btn-primary { background: #2563eb; color: #fff; }
.btn-primary:hover { background: #1d4ed8; text-decoration: none; }
.btn-secondary { background: #e2e8f0; color: #1e293b; }
.btn-secondary:hover { background: #cbd5e1; text-decoration: none; }
.btn-success { background: #16a34a; color: #fff; }
.btn-success:hover { background: #15803d; }

/* Cards */
.card {
  background: #fff;
  border-radius: 12px;
  padding: 1.5rem;
  box-shadow: 0 1px 3px rgba(0,0,0,.1);
  transition: box-shadow .2s;
}
.card:hover { box-shadow: 0 4px 12px rgba(0,0,0,.12); }
.card h3 { margin-bottom: .5rem; }
.card p { color: #64748b; font-size: .95rem; }

/* Grid */
.grid-3 { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 1.5rem; }
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 1.5rem; }
@media (max-width: 640px) { .grid-2 { grid-template-columns: 1fr; } }

/* Section */
.section { padding: 3rem 1rem; }
.section-title { text-align: center; margin-bottom: 2rem; }

/* Forms */
.form-group { margin-bottom: 1rem; }
.form-group label { display: block; font-weight: 600; margin-bottom: .35rem; font-size: .9rem; }
.form-group input, .form-group select, .form-group textarea {
  width: 100%;
  padding: .6rem .75rem;
  border: 1px solid #cbd5e1;
  border-radius: 8px;
  font-size: .95rem;
  font-family: inherit;
  background: #fff;
}
.form-group input:focus, .form-group select:focus, .form-group textarea:focus {
  outline: none;
  border-color: #2563eb;
  box-shadow: 0 0 0 3px rgba(37,99,235,.15);
}
textarea { resize: vertical; min-height: 100px; }

/* Calculator specific */
.calculator-card { max-width: 700px; margin: 0 auto; }
.subject-row { display: flex; gap: .75rem; align-items: end; margin-bottom: .75rem; }
.subject-row .form-group { flex: 1; margin-bottom: 0; }
.subject-row .btn { flex-shrink: 0; align-self: end; }
.result-box {
  background: #f0f7ff;
  border: 2px solid #2563eb;
  border-radius: 12px;
  padding: 1.5rem;
  text-align: center;
  margin-top: 1.5rem;
}
.result-box .result-value { font-size: 2.5rem; font-weight: 700; color: #2563eb; }
.result-box .result-label { color: #64748b; font-size: .9rem; }

/* FAQ */
.faq-item { border-bottom: 1px solid #e2e8f0; padding: 1rem 0; }
.faq-item h3 { font-size: 1rem; margin-bottom: .35rem; color: #1e293b; }
.faq-item p { color: #64748b; font-size: .9rem; }

/* Ad Placeholder */
.ad-placeholder {
  background: #f1f5f9;
  border: 2px dashed #cbd5e1;
  border-radius: 8px;
  padding: 2rem;
  text-align: center;
  color: #94a3b8;
  font-size: .85rem;
  margin: 1.5rem 0;
}

/* Footer */
.footer {
  background: #1e293b;
  color: #94a3b8;
  padding: 2.5rem 1rem 1.5rem;
  margin-top: 2rem;
}
.footer-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 1.5rem; margin-bottom: 1.5rem; }
.footer h4 { color: #fff; margin-bottom: .75rem; font-size: 1rem; }
.footer a { color: #94a3b8; font-size: .9rem; }
.footer a:hover { color: #fff; }
.footer ul li { margin-bottom: .35rem; }
.footer-bottom { border-top: 1px solid #334155; padding-top: 1rem; text-align: center; font-size: .85rem; }

/* Blog / Content */
.content-page { max-width: 750px; margin: 0 auto; padding: 2rem 1rem; }
.content-page h1 { margin-bottom: 1rem; }
.content-page h2 { margin-top: 2rem; margin-bottom: .75rem; }
.content-page p { margin-bottom: 1rem; color: #475569; }
.content-page ul, .content-page ol { margin-bottom: 1rem; padding-left: 1.5rem; }
.content-page li { margin-bottom: .35rem; color: #475569; }
.content-page ul { list-style: disc; }
.content-page ol { list-style: decimal; }

/* Breadcrumb */
.breadcrumb { padding: .75rem 1rem; font-size: .85rem; color: #64748b; }
.breadcrumb a { color: #2563eb; }

/* Disclaimer */
.disclaimer {
  background: #fffbeb;
  border: 1px solid #f59e0b;
  border-radius: 8px;
  padding: 1rem 1.25rem;
  font-size: .85rem;
  color: #92400e;
  margin: 1.5rem 0;
  line-height: 1.5;
}
.disclaimer strong { color: #78350f; }
.footer-disclaimer { font-size: .8rem; color: #64748b; margin-top: .75rem; line-height: 1.4; }

/* Trust Badges */
.trust-badges { display: flex; flex-wrap: wrap; gap: 1rem; justify-content: center; margin: 1.5rem 0; }
.trust-badge {
  background: #fff;
  border: 1px solid #e2e8f0;
  border-radius: 8px;
  padding: .6rem 1rem;
  font-size: .85rem;
  color: #475569;
  font-weight: 600;
  white-space: nowrap;
}

/* Related Tools */
.related-tools { background: #f8fafc; border-radius: 12px; padding: 1.5rem; margin: 1.5rem 0; }
.related-tools h3 { margin-bottom: .75rem; }
.related-tools a { display: inline-block; margin: .25rem .5rem .25rem 0; padding: .4rem .85rem; background: #2563eb; color: #fff; border-radius: 6px; font-size: .85rem; }
.related-tools a:hover { background: #1d4ed8; text-decoration: none; }

/* Error message for form validation */
.error-msg { color: #dc2626; font-size: .85rem; margin-top: .25rem; display: none; }
.input-error { border-color: #dc2626 !important; }

/* Last updated badge */
.last-updated { font-size: .8rem; color: #94a3b8; text-align: center; margin: 1rem 0; }

/* Hero CTA Button */
.hero .btn-hero {
  display: inline-block;
  margin-top: 1.5rem;
  padding: .85rem 2rem;
  background: #fff;
  color: #2563eb;
  font-size: 1.1rem;
  font-weight: 700;
  border-radius: 10px;
  border: none;
  cursor: pointer;
  transition: background .2s, transform .2s;
  text-decoration: none;
}
.hero .btn-hero:hover { background: #e0e7ff; transform: translateY(-2px); text-decoration: none; }

/* Share Section — Tool Share */
.share-section {
  background: #f8fafc;
  border: 1px dashed #cbd5e1;
  border-radius: 12px;
  padding: 1rem 1.5rem;
  margin-top: 1rem;
  text-align: center;
}
.share-section h4 {
  margin-bottom: .6rem;
  font-size: .9rem;
  color: #64748b;
  font-weight: 500;
}
.share-buttons { display: flex; gap: .75rem; justify-content: center; flex-wrap: wrap; }

/* WhatsApp button (used in tool share) */
.btn-whatsapp {
  background: #25D366;
  color: #fff;
  padding: .55rem 1.1rem;
  border-radius: 8px;
  font-weight: 600;
  font-size: .85rem;
  border: none;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: .4rem;
  transition: all .2s;
  text-decoration: none;
}
.btn-whatsapp svg { flex-shrink: 0; }
.btn-whatsapp:hover { background: #1ebe5d; text-decoration: none; color: #fff; transform: translateY(-1px); }

/* Copy Link button (used in tool share) */
.btn-copy-link {
  background: #e2e8f0;
  color: #1e293b;
  padding: .55rem 1.1rem;
  border-radius: 8px;
  font-weight: 600;
  font-size: .85rem;
  border: none;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: .4rem;
  transition: all .2s;
}
.btn-copy-link svg { flex-shrink: 0; }
.btn-copy-link:hover { background: #cbd5e1; transform: translateY(-1px); }
.btn-copy-link.copied { background: #16a34a; color: #fff; }

/* Dynamic Result Share — Primary CTA */
.result-share {
  background: linear-gradient(135deg, #eff6ff 0%, #f0f9ff 100%);
  border: 2px solid #93c5fd;
  border-radius: 16px;
  padding: 1.5rem;
  margin-top: 1.5rem;
  text-align: center;
  transition: opacity .4s ease;
  box-shadow: 0 4px 12px rgba(37, 99, 235, .08);
}
.result-share-header {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: .5rem;
  margin-bottom: .5rem;
}
.result-share-icon { font-size: 1.5rem; }
.result-share-header h4 {
  font-size: 1.1rem;
  color: #1e40af;
  font-weight: 700;
}
.result-share-text {
  font-size: .82rem;
  color: #475569;
  font-style: italic;
  margin-bottom: 1rem;
  line-height: 1.5;
  background: #fff;
  padding: .6rem .75rem;
  border-radius: 8px;
  border: 1px solid #e2e8f0;
}

/* Result share buttons — bigger and bolder */
.btn-share-result {
  background: #25D366;
  color: #fff;
  padding: .7rem 1.5rem;
  border-radius: 10px;
  font-weight: 700;
  font-size: .95rem;
  border: none;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: .5rem;
  transition: all .2s;
  box-shadow: 0 2px 8px rgba(37, 211, 102, .25);
}
.btn-share-result svg { flex-shrink: 0; }
.btn-share-result:hover { background: #1ebe5d; transform: translateY(-2px); box-shadow: 0 4px 12px rgba(37, 211, 102, .35); }

.btn-share-copy {
  background: #fff;
  color: #334155;
  padding: .7rem 1.5rem;
  border-radius: 10px;
  font-weight: 600;
  font-size: .95rem;
  border: 2px solid #e2e8f0;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: .5rem;
  transition: all .2s;
}
.btn-share-copy svg { flex-shrink: 0; }
.btn-share-copy:hover { border-color: #93c5fd; background: #f0f9ff; transform: translateY(-2px); }
.btn-share-copy.copied { background: #16a34a; color: #fff; border-color: #16a34a; }

/* Bookmark Reminder */
.bookmark-reminder {
  text-align: center;
  padding: 1rem;
  margin-top: 1rem;
  color: #64748b;
  font-size: .9rem;
  background: #fffbeb;
  border: 1px solid #fde68a;
  border-radius: 8px;
}

/* Result message above result */
.result-message {
  text-align: center;
  font-size: .9rem;
  color: #16a34a;
  font-weight: 600;
  margin-bottom: .75rem;
}

/* Most Used Tools Section */
.most-used-section { background: #fff; padding: 3rem 1rem; }
.most-used-section .card { border: 2px solid #e2e8f0; transition: border-color .2s, box-shadow .2s; }
.most-used-section .card:hover { border-color: #2563eb; box-shadow: 0 4px 16px rgba(37,99,235,.15); }
.fire-badge {
  display: inline-block;
  background: #fef2f2;
  color: #dc2626;
  font-size: .75rem;
  font-weight: 700;
  padding: .2rem .6rem;
  border-radius: 999px;
  margin-bottom: .5rem;
}

/* Calculator Tabs */
.calc-tabs {
  display: flex;
  gap: .5rem;
  margin-bottom: 1.5rem;
  border-bottom: 2px solid #e2e8f0;
  padding-bottom: 0;
}
.calc-tab {
  padding: .75rem 1.5rem;
  border: none;
  background: none;
  font-size: 1rem;
  font-weight: 600;
  color: #64748b;
  cursor: pointer;
  border-bottom: 3px solid transparent;
  margin-bottom: -2px;
  transition: all .2s ease;
}
.calc-tab:hover { color: #2563eb; }
.calc-tab.active {
  color: #2563eb;
  border-bottom-color: #2563eb;
}
.tab-content { display: none; }
.tab-content.active { display: block; }

/* Semester Row */
.semester-row {
  display: grid;
  grid-template-columns: auto 1fr 1fr auto;
  gap: .75rem;
  align-items: end;
  padding: .75rem 0;
  border-bottom: 1px solid #f1f5f9;
}
.semester-row .sem-label {
  font-weight: 600;
  color: #334155;
  padding-bottom: .5rem;
  white-space: nowrap;
}

/* Inline Calculator Error */
.calc-error {
  background: #fef2f2;
  border: 1px solid #fca5a5;
  color: #dc2626;
  font-size: .9rem;
  font-weight: 600;
  padding: .6rem 1rem;
  border-radius: 8px;
  margin-bottom: .75rem;
  text-align: center;
}

/* Utility */
.text-center { text-align: center; }
.mt-1 { margin-top: 1rem; }
.mt-2 { margin-top: 2rem; }
.mb-1 { margin-bottom: 1rem; }
.mb-2 { margin-bottom: 2rem; }
.hidden { display: none; }

/* Small phones */
@media (max-width: 480px) {
  h1 { font-size: 1.5rem; }
  h2 { font-size: 1.25rem; }
  .hero { padding: 2rem 0.75rem; }
  .hero h1 { font-size: 1.6rem; }
  .hero p { font-size: 0.95rem; }
  .hero .btn-hero { padding: .7rem 1.5rem; font-size: 1rem; }
  .section { padding: 2rem 0.75rem; }
  .container { padding: 0 0.75rem; }
  .grid-2 { grid-template-columns: 1fr; }
  .grid-3 { grid-template-columns: 1fr; }
  .card { padding: 1.1rem; }
  .result-box { padding: 1rem; }
  .result-box .result-value { font-size: 2rem; }
  .btn { padding: .6rem 1.2rem; font-size: .9rem; min-height: 44px; }
  .btn-primary { min-height: 44px; }
  .btn-share-result, .btn-share-copy { padding: .6rem 1rem; font-size: .85rem; min-height: 44px; }
  .btn-whatsapp, .btn-copy-link { min-height: 44px; }
  .form-group input, .form-group select { padding: .7rem .75rem; font-size: 1rem; min-height: 44px; }
  .subject-row { grid-template-columns: 1fr; gap: .5rem; }
  .calc-tabs { gap: .25rem; overflow-x: auto; }
  .calc-tab { padding: .6rem 1rem; font-size: .9rem; white-space: nowrap; }
  .semester-row { grid-template-columns: 1fr 1fr; gap: .5rem; }
  .share-buttons { flex-direction: column; align-items: center; }
  .result-share { padding: 1rem; }
  .footer-grid { grid-template-columns: 1fr; gap: 1rem; }
  .related-tools a { font-size: .8rem; padding: .35rem .7rem; }
  .breadcrumb { font-size: .8rem; padding: .5rem .75rem; }
  .faq-item h3 { font-size: .95rem; }
  .trust-badges { gap: .5rem; }
  .trust-badge { padding: .4rem .75rem; font-size: .8rem; }
}