html { scroll-behavior: smooth; }
body { font-family: 'Inter', sans-serif; }
.nav-link, .mobile-nav-link { font-size: .95rem; font-weight: 600; color: rgb(71 85 105); transition: color .2s ease; }
.nav-link:hover, .mobile-nav-link:hover { color: rgb(15 118 110); }

.panel-card {
  border: 1px solid rgba(148,163,184,.18);
  background: rgba(255,255,255,.82);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: 0 10px 30px rgba(15,23,42,.06);
  border-radius: 1.5rem;
}
.dark .panel-card { background: rgba(15,23,42,.78); border-color: rgba(100,116,139,.24); }

.feature-card {
  border: 1px solid rgba(148,163,184,.18);
  background: rgba(255,255,255,.75);
  border-radius: 1.25rem;
  padding: 1rem;
  box-shadow: 0 10px 24px rgba(15,23,42,.05);
}
.dark .feature-card { background: rgba(15,23,42,.72); border-color: rgba(100,116,139,.22); }

.input-field {
  border-radius: .9rem;
  border: 1px solid rgb(203 213 225);
  background: rgba(255,255,255,.95);
  padding: .85rem .95rem;
  outline: none;
  transition: border-color .2s ease, box-shadow .2s ease;
}
.input-field:focus {
  border-color: rgb(20 184 166);
  box-shadow: 0 0 0 4px rgba(20,184,166,.12);
}
.dark .input-field { border-color: rgb(51 65 85); background: rgba(15,23,42,.96); color: white; }

.section-tag {
  font-size: .78rem;
  font-weight: 800;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: rgb(15 118 110);
}
.section-title {
  margin-top: .5rem;
  font-size: 2rem;
  line-height: 1.15;
  font-weight: 800;
  letter-spacing: -.03em;
}
.section-subtitle { margin-top: .75rem; max-width: 52rem; color: rgb(71 85 105); }
.dark .section-subtitle { color: rgb(203 213 225); }

.content-wrap { margin-inline: auto; max-width: 80rem; padding: 3.5rem 1rem; }
.content-head { margin-bottom: 2rem; }
.content-grid { display: grid; gap: 1.5rem; }
@media (min-width: 1024px) { .content-grid { grid-template-columns: 1fr 1fr; } }
.content-title { font-size: 1.35rem; font-weight: 800; letter-spacing: -.02em; }
.sub-title { margin-top: 1.25rem; font-size: 1rem; font-weight: 700; }
.content-p { margin-top: .9rem; line-height: 1.8; color: rgb(71 85 105); }
.dark .content-p { color: rgb(203 213 225); }

.bullet-list { margin-top: 1rem; display: grid; gap: .8rem; }
.bullet-list li {
  position: relative;
  padding-left: 1.15rem;
  color: rgb(51 65 85);
}
.bullet-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: .6rem;
  height: .45rem;
  width: .45rem;
  border-radius: 999px;
  background: rgb(15 118 110);
}
.dark .bullet-list li { color: rgb(226 232 240); }

.quick-box {
  margin-top: 1.4rem;
  border-radius: 1rem;
  background: rgba(20,184,166,.08);
  padding: 1rem;
}
.quick-box h4 {
  font-size: .95rem;
  font-weight: 800;
  color: rgb(15 118 110);
}

.primary-btn {
  border-radius: 1rem;
  background: rgb(15 118 110);
  color: white;
  padding: .9rem 1.25rem;
  font-weight: 700;
  transition: transform .2s ease, background .2s ease;
}
.primary-btn:hover { transform: translateY(-1px); background: rgb(19 78 74); }

.topic-card, .mini-chip, .social-link {
  border-radius: 1.2rem;
  border: 1px solid rgba(148,163,184,.18);
  background: rgba(255,255,255,.85);
  padding: 1rem 1.15rem;
  transition: transform .2s ease, border-color .2s ease, box-shadow .2s ease;
  box-shadow: 0 10px 25px rgba(15,23,42,.05);
}
.topic-card:hover, .social-link:hover { transform: translateY(-2px); border-color: rgb(20 184 166); }
.topic-card h3 { font-size: 1.05rem; font-weight: 800; }
.topic-card p { margin-top: .55rem; font-size: .95rem; color: rgb(71 85 105); }
.dark .topic-card, .dark .mini-chip, .dark .social-link { background: rgba(15,23,42,.78); border-color: rgba(100,116,139,.22); }
.dark .topic-card p { color: rgb(203 213 225); }

.demo-stage { margin-top: 1.2rem; display: flex; align-items: center; gap: 1rem; }
.demo-node {
  min-width: 88px;
  border-radius: 1rem;
  background: rgba(20,184,166,.12);
  padding: 1rem;
  text-align: center;
  font-weight: 700;
}
.demo-line {
  position: relative;
  flex: 1;
  height: 12px;
  border-radius: 999px;
  background: linear-gradient(90deg, rgba(15,118,110,.15), rgba(8,145,178,.2));
}
.packet {
  position: absolute;
  left: 0;
  top: -8px;
  height: 28px;
  width: 28px;
  border-radius: 999px;
  background: linear-gradient(135deg, #14b8a6, #06b6d4);
  box-shadow: 0 8px 18px rgba(6,182,212,.35);
  transition: left 2.2s ease;
}

.device-btn, .topology-btn, .switch-btn {
  border-radius: .9rem;
  border: 1px solid rgb(203 213 225);
  background: rgba(255,255,255,.95);
  padding: .8rem 1rem;
  font-weight: 700;
  transition: all .2s ease;
}
.device-btn:hover, .topology-btn:hover, .switch-btn:hover {
  border-color: rgb(20 184 166);
  background: rgba(20,184,166,.08);
}
.dark .device-btn, .dark .topology-btn, .dark .switch-btn {
  border-color: rgb(51 65 85);
  background: rgba(15,23,42,.95);
}

.layer-card {
  border-radius: .9rem;
  background: rgba(15,118,110,.08);
  padding: .8rem 1rem;
  margin-bottom: .55rem;
  font-weight: 700;
  cursor: pointer;
  transition: transform .2s ease, background .2s ease, box-shadow .2s ease;
}
.layer-card:hover, .layer-card.active {
  transform: translateX(4px);
  background: rgba(20,184,166,.16);
  box-shadow: 0 8px 18px rgba(20,184,166,.12);
}
.layer-card-accent { background: rgba(8,145,178,.12); }
.layer-card-accent.active { background: rgba(8,145,178,.2); }

.switch-stage {
  min-height: 170px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: .75rem;
  flex-wrap: wrap;
}
.switch-block {
  border-radius: .9rem;
  background: rgba(20,184,166,.12);
  padding: .85rem 1rem;
  font-weight: 700;
}
.switch-packet {
  height: 38px;
  width: 38px;
  border-radius: .9rem;
  background: linear-gradient(135deg, #14b8a6, #06b6d4);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: .75rem;
  font-weight: 800;
  box-shadow: 0 10px 18px rgba(6,182,212,.2);
}

.question-card { border-radius: 1rem; border: 1px solid rgb(226 232 240); padding: 1rem; }
.dark .question-card { border-color: rgb(51 65 85); }

@media (max-width: 767px) {
  .section-title { font-size: 1.7rem; }
}