:root {
  --nav-h: calc(max(18px, env(safe-area-inset-top)) + 46px);
}

html {
  scroll-padding-top: var(--nav-h);
}

header.top {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 200;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding:
    max(18px, env(safe-area-inset-top))
    clamp(18px, 3.4vw, 40px)
    14px;
  font-family: "Syne", sans-serif;
  color: var(--ink, #f4f3ef);
  background: transparent;
  border-bottom: 1px solid transparent;
  transition: background 0.25s ease, border-color 0.25s ease;
  animation: nav-fade-down 0.7s ease both;
}

header.top.bar,
header.top.is-open {
  background: rgba(18, 20, 17, 0.82);
  -webkit-backdrop-filter: blur(12px);
  backdrop-filter: blur(12px);
  border-bottom-color: rgba(243, 242, 237, 0.14);
}

header.top .menu-btn {
  display: none;
  width: 42px;
  height: 42px;
  margin: -8px -8px -8px 0;
  padding: 0;
  border: 0;
  background: transparent;
  color: var(--ink, #f4f3ef);
  cursor: pointer;
}

header.top .menu-btn span,
header.top .menu-btn span::before,
header.top .menu-btn span::after {
  display: block;
  width: 18px;
  height: 1.5px;
  margin: 0 auto;
  background: currentColor;
  position: relative;
}

header.top .menu-btn span::before,
header.top .menu-btn span::after {
  content: "";
  position: absolute;
  left: 0;
}

header.top .menu-btn span::before { top: -6px; }
header.top .menu-btn span::after { top: 6px; }

header.top.is-open .menu-btn span { background: transparent; }
header.top.is-open .menu-btn span::before {
  top: 0;
  transform: rotate(45deg);
}
header.top.is-open .menu-btn span::after {
  top: 0;
  transform: rotate(-45deg);
}

header.top .brand {
  display: flex;
  align-items: center;
  gap: 8px;
  line-height: 0;
}

header.top .brand img {
  display: block;
  width: auto;
  filter: brightness(0) invert(1);
}

header.top .brand .logo-hex { height: clamp(20px, 2.2vw, 28px); }
header.top .brand .logo-word {
  height: clamp(15px, 1.8vw, 22px);
  transform: translateY(3px);
}

header.top .nav {
  display: flex;
  align-items: center;
  gap: clamp(14px, 2.2vw, 26px);
  font-size: 13px;
  font-weight: 500;
  letter-spacing: 0.04em;
}

header.top .nav a {
  position: relative;
  display: inline-block;
  text-align: center;
  opacity: 0.78;
  padding-bottom: 4px;
  color: inherit;
  text-decoration: none;
  background-image: linear-gradient(var(--signal, #3dba8a), var(--signal, #3dba8a));
  background-repeat: no-repeat;
  background-position: right bottom;
  background-size: 0% 1.5px;
  transition: opacity 0.3s ease, color 0.35s ease, background-size 0.5s cubic-bezier(0.25, 0.8, 0.25, 1);
}

header.top .nav a::before {
  content: attr(data-text);
  display: block;
  height: 0;
  overflow: hidden;
  visibility: hidden;
  font-family: "IBM Plex Mono", ui-monospace, monospace;
}

header.top .nav a::after {
  content: attr(data-text);
  position: absolute;
  left: 0;
  right: 0;
  top: 0;
  font-family: "IBM Plex Mono", ui-monospace, monospace;
  color: var(--ink, #f4f3ef);
  white-space: nowrap;
  opacity: 0;
  transform: translateY(45%);
  transition: opacity 0.35s cubic-bezier(0.25, 0.8, 0.25, 1), transform 0.35s cubic-bezier(0.25, 0.8, 0.25, 1);
  pointer-events: none;
}

header.top .nav a:hover {
  opacity: 1;
  color: transparent;
  background-position: left bottom;
  background-size: 100% 1.5px;
}

header.top .nav a:hover::after {
  opacity: 1;
  transform: translateY(0);
}

header.top .nav a[aria-current="page"] {
  opacity: 1;
  color: var(--signal, #3dba8a);
}

header.top .nav a[aria-current="page"]::after { color: var(--signal, #3dba8a); }
header.top .nav a[aria-current="page"]:hover { color: transparent; }
header.top .nav .talk { opacity: 1; }

header.top ~ .wrap {
  padding-top: var(--nav-h);
}

@keyframes nav-fade-down {
  from { opacity: 0; transform: translateY(-10px); }
  to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 860px) {
  header.top {
    flex-wrap: wrap;
    padding: max(14px, env(safe-area-inset-top)) clamp(18px, 3.4vw, 40px) 12px;
  }

  header.top .menu-btn { display: grid; place-items: center; }

  header.top .nav {
    display: none;
    flex-basis: 100%;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 6px 0 10px;
  }

  header.top.is-open .nav { display: flex; }

  header.top .nav .hide-sm { display: inline-block; }

  header.top .nav a {
    text-align: left;
    padding: 12px 0;
    opacity: 1;
    font-size: 15px;
  }

  header.top .brand .logo-hex { height: 18px; }
  header.top .brand .logo-word {
    height: 14px;
    max-width: min(80px, 24vw);
    object-fit: contain;
    transform: translateY(2px);
  }
}

@media (max-width: 560px) {
  header.top .nav { font-size: 15px; }
}

@media (prefers-reduced-motion: reduce) {
  header.top { animation: none; }
}