/* Top fixed navigation bar (academic / classic serif) */
:root{
  --topnav-height: 72px;
  --topnav-max-width: 1120px;

  --topnav-pad-x: 18px;
  --topnav-gap: 12px;

  --topnav-item-height: 40px;
  --topnav-item-radius: 10px;

  --topnav-center-gap: 16px;

  --topnav-side-shift: 6px;

  /* B: classic serif (publisher / paper-like) */
  --topnav-font: "Palatino Linotype", Palatino, "Book Antiqua",
                 "Times New Roman", "Noto Serif", "Songti SC", STSong, "SimSun", serif;

  --topnav-focus-ring: 0 0 0 3px var(--accent-weak);
}

.top-nav{
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: var(--topnav-height);
  z-index: 12000;

  display: flex;
  align-items: center;

  background:
    linear-gradient(
      180deg,
      color-mix(in srgb, var(--nav-surface) 92%, transparent),
      var(--nav-surface)
    ),
    var(--paper-texture);
  border-bottom: 1px solid var(--nav-border);

  backdrop-filter: blur(6px);
  -webkit-backdrop-filter: blur(6px);

  box-shadow: var(--nav-shadow);

  opacity: 0;
  transform: translateY(-6px);
  pointer-events: none;
  transition: opacity 0.28s ease, transform 0.28s ease;
}

body.nav-visible .top-nav{
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}

.top-nav .top-nav-inner{
  width: min(var(--topnav-max-width), 100%);
  margin: 0 auto;
  padding: 0 var(--topnav-pad-x);

  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: var(--topnav-gap);
}

.top-nav-left,
.top-nav-right{
  display: flex;
  align-items: center;
  gap: 10px;
}

.top-nav-left,
.top-nav-right{
  transform: translateX(var(--topnav-side-shift));
}

.top-nav-left{ justify-content: flex-start; }
.top-nav-right{ justify-content: flex-end; }

.top-nav-center{
  display: flex;
  align-items: center;
  justify-content: center;

  gap: var(--topnav-center-gap);
}

/* ---------- Icon buttons ---------- */
.top-nav-icon{
  width: var(--topnav-item-height);
  height: var(--topnav-item-height);
  border-radius: var(--topnav-item-radius);

  display: inline-flex;
  align-items: center;
  justify-content: center;

  cursor: pointer;
  user-select: none;

  background: transparent;
  color: var(--accent);
  border: 1px solid transparent;
  box-shadow: none;

  transition: background-color 0.18s ease, border-color 0.18s ease, color 0.18s ease;
}

.top-nav-icon:hover{
  background: var(--surface-2);
  border-color: var(--border);
  color: var(--accent-strong);
}

.top-nav-icon:active{
  background: var(--surface);
}

.top-nav-icon:focus-visible{
  outline: none;
  border-color: color-mix(in srgb, var(--accent) 40%, var(--border));
  box-shadow: var(--topnav-focus-ring);
}

/* ---------- Clock ---------- */
.top-nav-clock{
  height: var(--topnav-item-height);
  padding: 0 12px;
  border-radius: var(--topnav-item-radius);

  display: inline-flex;
  align-items: center;
  justify-content: center;

  background: transparent;
  border: transparent;

  font-family: var(--topnav-font);
  font-weight: 600;
  font-size: 0.95em;
  letter-spacing: 0.2px;
  font-variant-numeric: tabular-nums;
  color: var(--muted);

  user-select: none;
}

/* ---------- Nav links (underline indicates state) ---------- */
.top-nav-link{
  position: relative;

  height: var(--topnav-item-height);
  padding: 0 14px;
  border-radius: var(--topnav-item-radius);

  display: inline-flex;
  align-items: center;
  justify-content: center;

  background: transparent;
  color: var(--text);
  border: 1px solid transparent;
  box-shadow: none;

  font-family: var(--topnav-font);
  font-weight: 600;
  font-size: 1.10em;
  font-variant: small-caps;
  letter-spacing: 0.45px;

  cursor: pointer;
  -webkit-appearance: none;
  appearance: none;

  transition: background-color 0.18s ease, border-color 0.18s ease, color 0.18s ease;
}

.top-nav-link::after{
  content: "";
  position: absolute;
  left: 12px;
  right: 12px;
  bottom: 6px;
  height: 2px;

  background: transparent;
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.18s ease, background-color 0.18s ease;
}

.top-nav-link:hover{
  background: var(--surface-2);
  border-color: var(--border);
  color: var(--accent-strong);
}

.top-nav-link:hover::after{
  background: color-mix(in srgb, var(--accent) 55%, transparent);
  transform: scaleX(1);
}

.top-nav-link:active{
  background: var(--surface);
}

.top-nav-link:focus-visible{
  outline: none;
  border-color: color-mix(in srgb, var(--accent) 40%, var(--border));
  box-shadow: var(--topnav-focus-ring);
}

.top-nav-link.active{
  background: transparent;
  border-color: transparent;
  color: var(--accent-strong);
}

.top-nav-link.active::after{
  background: var(--accent);
  transform: scaleX(1);
}

/* ---------- Reduced motion ---------- */
@media (prefers-reduced-motion: reduce){
  .top-nav, .top-nav-link, .top-nav-icon{ transition: none !important; }
}

/* ---------- Responsive ---------- */
@media (max-width: 560px){
  :root{
    --topnav-height: 60px;

    --topnav-center-gap: 10px;

    --topnav-side-shift: 3px;
  }

  .top-nav .top-nav-inner{
    padding: 0 12px;
    gap: 10px;
  }

  .top-nav-link{
    padding: 0 10px;
    letter-spacing: 0.35px;
  }

  .top-nav-clock{ display: none; }
}

/* Hide legacy fixed controls (moved into top-nav) */
#toggle-btn, #toggle-btn-social, #toggle-btn-toolkit, #toggle-btn-schedule,
#clock, #clock-social, #clock-toolkit, #clock-schedule,
#resume-back-btn, #social-back-btn, #toolkit-back-btn, #schedule-back-btn,
.clock-toggle{
  display: none !important;
}