:root {
  --signal-blue: #2C6BED;
  --signal-blue-dark: #1E54C7;
  --signal-ink: #1B1B1B;
  --signal-sub: #4A5568;
  --signal-bg: #FFFFFF;
  --signal-gray: #F6F7F9;
  --signal-border: #E2E8F0;
  --footer-bg: #12161F;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Kaku Gothic ProN", "Noto Sans JP", "Noto Sans SC", "Noto Sans KR", sans-serif;
  color: var(--signal-ink);
  background: var(--signal-bg);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
}

.container {
  max-width: 1160px;
  margin: 0 auto;
  padding: 0 24px;
}

/* Sticky Signal-style Top Bar */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--signal-border);
}

.nav-inner {
  height: 74px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--signal-ink);
}
.brand-icon {
  width: 38px;
  height: 38px;
  border-radius: 10px;
}
.brand-word {
  font-size: 22px;
  font-weight: 800;
  letter-spacing: -0.02em;
}
.p2p-pill {
  font-size: 11px;
  font-weight: 800;
  color: var(--signal-blue);
  background: rgba(44, 107, 237, 0.11);
  padding: 3px 8px;
  border-radius: 999px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 24px;
}
.nav-links a {
  text-decoration: none;
  color: var(--signal-ink);
  font-size: 14.5px;
  font-weight: 600;
  transition: color 0.15s;
}
.nav-links a:hover {
  color: var(--signal-blue);
}
.nav-links .github-link {
  color: var(--signal-blue);
}

.lang-select {
  appearance: auto;
  border: 1px solid var(--signal-border);
  background: #fff;
  color: var(--signal-ink);
  padding: 7px 12px;
  border-radius: 8px;
  font-size: 13.5px;
  font-weight: 600;
  cursor: pointer;
}

/* Signal Royal-Blue Hero */
.hero-section {
  background: var(--signal-blue);
  color: #ffffff;
  padding: 76px 0 88px;
  overflow: hidden;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 48px;
  align-items: center;
}

.hero-kicker {
  display: inline-block;
  font-size: 12px;
  font-weight: 800;
  letter-spacing: 0.1em;
  background: rgba(255, 255, 255, 0.16);
  padding: 5px 12px;
  border-radius: 999px;
  margin-bottom: 18px;
}

.hero-copy h1 {
  font-size: clamp(34px, 4.6vw, 54px);
  font-weight: 800;
  line-height: 1.16;
  letter-spacing: -0.025em;
  margin-bottom: 20px;
}

.hero-lead {
  font-size: 18px;
  line-height: 1.65;
  color: rgba(255, 255, 255, 0.92);
  margin-bottom: 30px;
}

.hero-cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  margin-bottom: 20px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  font-weight: 700;
  font-size: 15px;
  padding: 13px 24px;
  border-radius: 10px;
  transition: transform 0.14s ease, background 0.14s ease;
  cursor: pointer;
}
.btn:hover {
  transform: translateY(-1px);
}
.btn-white {
  background: #ffffff;
  color: var(--signal-blue);
}
.btn-outline-white {
  border: 2px solid rgba(255, 255, 255, 0.78);
  color: #ffffff;
}
.btn-primary {
  background: var(--signal-blue);
  color: #ffffff;
}
.btn-primary:hover {
  background: var(--signal-blue-dark);
}
.btn-outline {
  border: 2px solid var(--signal-blue);
  color: var(--signal-blue);
  background: transparent;
}

.hero-trust-note {
  font-size: 13px;
  color: rgba(255, 255, 255, 0.85);
  font-weight: 600;
}

/* Hero Smartphone Mockup */
.hero-devices {
  display: flex;
  justify-content: center;
}
.phone-mockup {
  width: 340px;
  background: #0f172a;
  color: #f8fafc;
  border-radius: 34px;
  border: 6px solid #1e293b;
  box-shadow: 0 28px 65px rgba(9, 25, 66, 0.45);
  overflow: hidden;
  transform: rotate(-2deg);
}
.phone-topbar {
  background: #008069;
  padding: 14px 16px;
  display: flex;
  align-items: center;
  gap: 10px;
}
.phone-topbar img {
  width: 32px;
  height: 32px;
  border-radius: 8px;
}
.phone-topbar strong {
  display: block;
  font-size: 14px;
}
.phone-topbar span {
  font-size: 10.5px;
  opacity: 0.9;
}
.mock-lock {
  margin-left: auto;
  background: rgba(0, 0, 0, 0.25);
  padding: 3px 8px;
  border-radius: 999px;
  font-weight: 700;
}
.phone-body {
  padding: 16px 14px 22px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.mock-sys {
  font-size: 11px;
  text-align: center;
  background: rgba(44, 107, 237, 0.2);
  color: #93c5fd;
  padding: 5px 10px;
  border-radius: 8px;
}
.mock-bubble {
  padding: 10px 12px;
  border-radius: 14px;
  font-size: 13px;
  line-height: 1.45;
  max-width: 88%;
}
.mock-bubble.incoming {
  background: #1e293b;
  align-self: flex-start;
  border-bottom-left-radius: 3px;
}
.mock-bubble.outgoing {
  background: #005c4b;
  align-self: flex-end;
  border-bottom-right-radius: 3px;
}
.mock-author {
  font-size: 11px;
  font-weight: 700;
  color: #38bdf8;
  margin-bottom: 2px;
}

/* Editorial Sections */
.section-white {
  padding: 88px 0;
  background: var(--signal-bg);
}
.section-gray {
  padding: 88px 0;
  background: var(--signal-gray);
}

.section-heading {
  max-width: 780px;
  margin-bottom: 48px;
}
.section-heading.center {
  margin-left: auto;
  margin-right: auto;
  text-align: center;
}
.section-eyebrow {
  display: inline-block;
  font-size: 12px;
  font-weight: 800;
  letter-spacing: 0.09em;
  color: var(--signal-blue);
  margin-bottom: 8px;
}
.section-heading h2,
.split-text h2 {
  font-size: clamp(28px, 3.3vw, 40px);
  font-weight: 800;
  line-height: 1.22;
  letter-spacing: -0.02em;
  margin-bottom: 16px;
}

.declaration-box {
  margin-top: 18px;
  background: rgba(44, 107, 237, 0.07);
  border-left: 4px solid var(--signal-blue);
  padding: 18px 22px;
  border-radius: 10px;
  font-size: 16px;
  font-weight: 600;
  color: var(--signal-ink);
  text-align: left;
}

.three-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 26px;
}
.editorial-card {
  background: var(--signal-gray);
  border-radius: 18px;
  padding: 32px 28px;
  border: 1px solid var(--signal-border);
}
.card-icon {
  width: 52px;
  height: 52px;
  border-radius: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;
  margin-bottom: 18px;
}
.blue-tint {
  background: rgba(44, 107, 237, 0.12);
}
.editorial-card h3 {
  font-size: 20px;
  margin-bottom: 10px;
}
.editorial-card p {
  color: var(--signal-sub);
  font-size: 15px;
}

/* Split Interactive Group Section */
.split-section {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
  align-items: center;
}
.split-text p {
  font-size: 16px;
  color: var(--signal-sub);
  margin-bottom: 22px;
}
.style-toggle-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 22px;
}
.style-switch-btn {
  border: 2px solid var(--signal-border);
  background: #ffffff;
  color: var(--signal-ink);
  padding: 10px 16px;
  border-radius: 10px;
  font-weight: 700;
  font-size: 13.5px;
  cursor: pointer;
}
.style-switch-btn.active {
  border-color: var(--signal-blue);
  background: var(--signal-blue);
  color: #ffffff;
}
.check-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.check-list li {
  font-size: 14.5px;
  font-weight: 600;
  padding-left: 24px;
  position: relative;
}
.check-list li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: var(--signal-blue);
  font-weight: 900;
}

.group-preview-window {
  background: #ffffff;
  border-radius: 20px;
  overflow: hidden;
  box-shadow: 0 22px 50px rgba(15, 23, 42, 0.14);
  border: 1px solid var(--signal-border);
}
.hidden {
  display: none !important;
}
.gp-header {
  padding: 15px 18px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  color: #fff;
}
.gp-header.tg {
  background: #2481CC;
}
.gp-header.tg span {
  display: block;
  font-size: 11.5px;
  opacity: 0.9;
}
.gp-header.dc {
  background: #2B2D31;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}
.gp-badge {
  font-size: 10px;
  font-weight: 800;
  padding: 3px 8px;
  border-radius: 6px;
  background: rgba(255, 255, 255, 0.2);
}
.gp-badge.dc {
  background: #5865F2;
}
.gp-pin {
  background: #E8F4FD;
  color: #1A5A96;
  padding: 8px 18px;
  font-size: 12.5px;
  font-weight: 600;
}
.gp-messages {
  background: #E6EBEE;
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  min-height: 230px;
}
.gp-tg-bubble {
  background: #ffffff;
  padding: 11px 14px;
  border-radius: 14px;
  max-width: 82%;
  font-size: 13.5px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
}
.gp-tg-bubble.self {
  background: #EEFFDE;
  align-self: flex-end;
}
.gp-channel-layout,
.gp-channel-layout {
  display: flex;
  min-height: 300px;
  color: #dbdee1;
}
.gp-channel-rail,
.gp-channel-rail {
  width: 155px;
  background: #1E1F22;
  padding: 14px 10px;
  display: flex;
  flex-direction: column;
  gap: 5px;
}
.gp-server-name {
  font-weight: 800;
  font-size: 13px;
  color: #fff;
  padding-bottom: 10px;
  margin-bottom: 4px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}
.gp-ch {
  font-size: 12.5px;
  padding: 6px 8px;
  border-radius: 6px;
  color: #949ba4;
  font-weight: 600;
}
.gp-ch.active {
  background: rgba(88, 101, 242, 0.35);
  color: #fff;
}
.gp-channel-main,
.gp-channel-main {
  flex: 1;
  background: #313338;
  display: flex;
  flex-direction: column;
}
.gp-dc-feed {
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}
.gp-dc-item {
  display: flex;
  gap: 10px;
  font-size: 13px;
}
.gp-dc-av {
  width: 34px;
  height: 34px;
  border-radius: 50%;
  background: #5865F2;
  color: #fff;
  font-weight: 800;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}
.gp-role {
  font-size: 9.5px;
  background: rgba(88, 101, 242, 0.3);
  color: #c7d2fe;
  padding: 1px 5px;
  border-radius: 4px;
  margin-left: 4px;
}

/* 2x2 Privacy Features */
.two-by-two-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(420px, 1fr));
  gap: 26px;
}
.feature-box {
  background: var(--signal-gray);
  border: 1px solid var(--signal-border);
  border-radius: 18px;
  padding: 32px;
}
.feat-tag {
  font-size: 11px;
  font-weight: 800;
  color: var(--signal-blue);
  letter-spacing: 0.08em;
  margin-bottom: 8px;
}
.feature-box h3 {
  font-size: 21px;
  margin-bottom: 12px;
}
.feature-box p {
  font-size: 15px;
  color: var(--signal-sub);
}

/* Download & Developer Banner */
.download-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 26px;
  margin-bottom: 36px;
}
.download-card {
  background: #ffffff;
  border: 1px solid var(--signal-border);
  border-radius: 20px;
  padding: 34px;
  box-shadow: 0 8px 26px rgba(15, 23, 42, 0.05);
}
.dl-platform-badge {
  display: inline-block;
  font-size: 11px;
  font-weight: 800;
  color: var(--signal-blue);
  background: rgba(44, 107, 237, 0.1);
  padding: 4px 10px;
  border-radius: 999px;
  margin-bottom: 12px;
}
.download-card h3 {
  font-size: 24px;
  margin-bottom: 10px;
}
.download-card p {
  color: var(--signal-sub);
  font-size: 15px;
  margin-bottom: 22px;
}
.dl-btn-group {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.developer-banner {
  background: var(--signal-blue);
  color: #ffffff;
  border-radius: 20px;
  padding: 34px 38px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}
.developer-banner .section-eyebrow {
  color: rgba(255, 255, 255, 0.85);
}
.developer-banner h3 {
  font-size: 24px;
  margin-bottom: 6px;
}
.developer-banner p {
  color: rgba(255, 255, 255, 0.9);
  font-size: 15px;
}

/* Footer */
.site-footer {
  background: var(--footer-bg);
  color: #cbd5e1;
  padding: 64px 0;
}
.footer-grid {
  display: grid;
  grid-template-columns: 1.6fr 1fr 1fr 1fr;
  gap: 32px;
}
.footer-brand p {
  margin-top: 14px;
  font-size: 14px;
  color: #94a3b8;
  max-width: 320px;
}
.footer-col {
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.footer-col h4 {
  color: #ffffff;
  font-size: 14px;
  margin-bottom: 4px;
}
.footer-col a {
  color: #94a3b8;
  text-decoration: none;
  font-size: 14px;
}
.footer-col a:hover {
  color: #ffffff;
}

@media (max-width: 920px) {
  .hero-grid,
  .split-section,
  .two-by-two-grid,
  .footer-grid {
    grid-template-columns: 1fr;
  }
  .nav-links {
    display: none;
  }
  .developer-banner {
    flex-direction: column;
    align-items: flex-start;
  }
}