:root {
  --os-ink: #1c2430;
  --os-soft: #5c6774;
  --os-navy: #1e2a3a;
  --os-steel: #3d5a73;
  --os-sage: #4f7d68;
  --os-brass: #a67c52;
  --os-sand: #f4efe6;
  --os-paper: #fffdf9;
  --os-line: rgba(30, 42, 58, 0.12);
  --os-shadow: 0 18px 40px rgba(30, 42, 58, 0.08);
  --bs-primary: #3d5a73;
  --bs-primary-rgb: 61, 90, 115;
  --bs-body-color: #1c2430;
  --bs-body-bg: #f4efe6;
  --bs-body-font-family: "Figtree", "Segoe UI", sans-serif;
  --bs-heading-color: #1e2a3a;
  --bs-border-radius: 1rem;
  --bs-link-color: #3d5a73;
  --bs-link-hover-color: #1e2a3a;
}

html { scroll-behavior: smooth; }

body.os-body {
  color: var(--os-ink);
  background:
    radial-gradient(720px 380px at 100% -10%, rgba(166, 124, 82, 0.16), transparent 60%),
    radial-gradient(680px 420px at -10% 8%, rgba(79, 125, 104, 0.14), transparent 55%),
    var(--os-sand);
}

h1, h2, h3, .os-display {
  font-family: "Fraunces", Georgia, serif;
  font-weight: 560;
  letter-spacing: -0.03em;
}

.os-nav {
  background: rgba(255, 253, 249, 0.86);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid transparent;
  transition: border-color 0.3s ease, box-shadow 0.3s ease;
}

.os-nav.is-stuck {
  border-bottom-color: var(--os-line);
  box-shadow: 0 10px 30px rgba(30, 42, 58, 0.06);
}

.os-brand {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  font-family: "Fraunces", Georgia, serif;
  font-size: 1.35rem;
  color: var(--os-navy);
}

.os-brand img {
  width: 36px;
  height: 36px;
  border-radius: 8px;
}

.os-nav .nav-link {
  color: var(--os-ink);
  font-weight: 600;
  border-radius: 999px;
  padding: 0.45rem 0.85rem;
}

.os-nav .nav-link:hover,
.os-nav .nav-link:focus,
.os-nav .nav-link.show {
  color: var(--os-navy);
  background: rgba(61, 90, 115, 0.08);
}

.os-nav .dropdown-menu {
  border: 1px solid var(--os-line);
  border-radius: 16px;
  box-shadow: var(--os-shadow);
  padding: 0.45rem;
  background: var(--os-paper);
}

.os-nav .dropdown-item {
  border-radius: 10px;
  font-weight: 600;
  padding: 0.55rem 0.8rem;
}

.os-nav .dropdown-item:hover { background: var(--os-sand); }

.btn-os {
  border-radius: 999px;
  font-weight: 700;
  padding: 0.75rem 1.2rem;
  border: 1px solid transparent;
  transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
}

.btn-os:hover { transform: translateY(-2px); }

.btn-os-steel {
  background: var(--os-steel);
  color: #fff;
  box-shadow: 0 12px 24px rgba(61, 90, 115, 0.22);
}

.btn-os-steel:hover { background: var(--os-navy); color: #fff; }

.btn-os-sage {
  background: var(--os-sage);
  color: #fff;
}

.btn-os-sage:hover { background: #3d6654; color: #fff; }

.btn-os-ghost {
  background: rgba(255, 253, 249, 0.8);
  border-color: var(--os-line);
  color: var(--os-navy);
}

.btn-os-line {
  background: transparent;
  border-color: rgba(255, 253, 249, 0.45);
  color: #fff;
}

.btn-os-line:hover { background: rgba(255, 253, 249, 0.12); color: #fff; }

.os-hero { padding: 4.5rem 0 3rem; }

.os-kicker {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--os-brass);
}

.os-hero h1 {
  font-size: clamp(2.4rem, 5vw, 4.3rem);
  line-height: 1.05;
  margin: 0.6rem 0 0.8rem;
}

.os-motto {
  font-family: "Fraunces", Georgia, serif;
  font-size: clamp(1.15rem, 2vw, 1.45rem);
  color: var(--os-steel);
  margin-bottom: 1rem;
}

.os-lead {
  font-size: 1.08rem;
  line-height: 1.7;
  color: var(--os-soft);
  max-width: 38rem;
}

.os-hero-figure {
  background: var(--os-paper);
  border: 1px solid rgba(255, 255, 255, 0.9);
  border-radius: 28px;
  box-shadow: var(--os-shadow);
  padding: 1rem;
  overflow: hidden;
}

.os-hero-figure img,
.os-diagram {
  width: 100%;
  height: auto;
  display: block;
  border-radius: 18px;
}

.os-panel {
  background: rgba(255, 253, 249, 0.9);
  border: 1px solid rgba(255, 255, 255, 0.95);
  border-radius: 28px;
  box-shadow: var(--os-shadow);
  padding: clamp(1.25rem, 2.4vw, 2rem);
}

.os-section { padding: 1rem 0 2.4rem; }

.os-section h2 {
  font-size: clamp(1.8rem, 3vw, 2.6rem);
  margin-bottom: 0.6rem;
}

.os-tabs .nav-link {
  color: var(--os-ink);
  font-weight: 700;
  border-radius: 999px;
  border: 1px solid transparent;
}

.os-tabs .nav-link.active {
  background: var(--os-navy);
  color: #fff;
}

.os-chip {
  display: inline-flex;
  align-items: center;
  border-radius: 999px;
  padding: 0.4rem 0.75rem;
  background: var(--os-sand);
  color: var(--os-navy);
  font-weight: 600;
  font-size: 0.92rem;
  border: 1px solid var(--os-line);
}

.os-accordion .accordion-item {
  border: 1px solid var(--os-line);
  border-radius: 16px !important;
  overflow: hidden;
  margin-bottom: 0.6rem;
  background: var(--os-paper);
}

.os-accordion .accordion-button {
  font-weight: 700;
  background: var(--os-paper);
  color: var(--os-navy);
  box-shadow: none;
}

.os-accordion .accordion-button:not(.collapsed) {
  background: #f7f1ea;
  color: var(--os-navy);
}

.os-accordion .accordion-button:focus {
  box-shadow: 0 0 0 0.2rem rgba(61, 90, 115, 0.18);
}

.os-vpn-band {
  background: linear-gradient(135deg, #243044 0%, #3d5a73 58%, #4f7d68 140%);
  color: #f7f1ea;
  border-radius: 28px;
  padding: clamp(1.3rem, 3vw, 2rem);
  box-shadow: 0 20px 44px rgba(30, 42, 58, 0.18);
}

.os-vpn-band h2,
.os-vpn-band p { color: inherit; }

.os-vpn-band p { color: rgba(247, 241, 234, 0.88); }

.os-note {
  border-left: 4px solid var(--os-brass);
  background: #f7f1ea;
  border-radius: 16px;
  padding: 1rem 1.1rem;
}

.os-note code,
code.os-code {
  font-size: 0.86em;
  color: #6b3f22;
  background: rgba(166, 124, 82, 0.12);
  padding: 0.1rem 0.35rem;
  border-radius: 6px;
}

.os-step {
  display: flex;
  gap: 0.85rem;
  margin-bottom: 1rem;
}

.os-step-num {
  flex: 0 0 2rem;
  height: 2rem;
  border-radius: 50%;
  background: var(--os-steel);
  color: #fff;
  display: grid;
  place-items: center;
  font-weight: 800;
}

.os-loc {
  border-radius: 18px;
  background: var(--os-paper);
  border: 1px solid var(--os-line);
  padding: 1rem;
  height: 100%;
}

.os-loc strong { display: block; font-family: Fraunces, Georgia, serif; font-size: 1.2rem; }

.os-footer {
  color: var(--os-soft);
  padding: 1rem 0 2.4rem;
  font-size: 0.95rem;
}

.os-footer a { color: var(--os-steel); font-weight: 700; }

[data-reveal] {
  opacity: 0;
  transform: translateY(18px);
  animation: osRise 0.8s cubic-bezier(.2, .7, .2, 1) forwards;
}

[data-reveal="2"] { animation-delay: 0.12s; }
[data-reveal="3"] { animation-delay: 0.22s; }

.os-swap {
  animation: osFade 0.45s ease;
}

@keyframes osRise {
  to { opacity: 1; transform: none; }
}

@keyframes osFade {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: none; }
}

.tab-pane.fade.show { animation: osFade 0.4s ease; }

@media (max-width: 991px) {
  .os-hero { padding-top: 2.2rem; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  [data-reveal], .tab-pane.fade.show, .os-swap { animation: none; opacity: 1; transform: none; }
  .btn-os { transition: none; }
}