/* =====================================================================
   STICKY HEADER  —  colors come from data-theme tokens (tokens.css).
   ===================================================================== */

.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: var(--header-height);
  display: flex;
  align-items: center;
  /* color transitions smoothly as the theme flips on scroll */
  transition: background var(--transition), box-shadow var(--transition);
}

.site-header__inner {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
}

/* Subtle frosted backing once the user scrolls (set by header.js) */
.site-header.is-scrolled[data-theme="light"] {
  background: rgba(20, 20, 20, 0.55);
  backdrop-filter: blur(10px);
}
.site-header.is-scrolled[data-theme="dark"] {
  background: rgba(255, 255, 255, 0.7);
  backdrop-filter: blur(10px);
  box-shadow: 0 1px 0 rgba(0, 0, 0, 0.06);
}

/* ---- Logo ----------------------------------------------------------- */
.logo {
  display: inline-flex;
  align-items: center;
  gap: 0.65rem;
}
.logo__mark { flex: none; }
.logo__mark path { transition: fill var(--transition); }

.logo__wordmark {
  font-family: var(--font-heading);
  font-weight: var(--fw-bold);
  font-size: 1.35rem;
  letter-spacing: -0.01em;
  color: var(--logo-wordmark);
  transition: color var(--transition);
}
.logo__wordmark em { font-style: normal; color: var(--accent); }

/* ---- Nav ------------------------------------------------------------ */
.site-nav__list {
  display: flex;
  gap: clamp(1.25rem, 3vw, 2.5rem);
}
.site-nav a {
  font-family: var(--font-heading); /* Helvetica Now */
  font-weight: var(--fw-medium);
  font-size: 1.15rem;
  letter-spacing: 0.01em;
  color: var(--header-text);
  position: relative;
  padding: 0.25rem 0;
  transition: color var(--transition);
}
/* animated underline */
.site-nav a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -2px;
  width: 100%;
  height: 2px;
  background: var(--accent);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--transition);
}
.site-nav a:hover { color: var(--header-text-hover); }
.site-nav a:hover::after { transform: scaleX(1); }

/* ---- Header actions (account link + mobile toggle), right side ----- */
.site-header__actions {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.account-link {
  font-family: var(--font-heading);
  font-weight: var(--fw-medium);
  font-size: 0.95rem;
  letter-spacing: 0.01em;
  color: var(--header-text);
  border: 1.5px solid currentColor;
  border-radius: var(--radius);
  padding: 0.5em 1.1em;
  transition: background var(--transition), color var(--transition), border-color var(--transition);
  white-space: nowrap;
}
.account-link:hover { background: var(--accent); border-color: var(--accent); color: #fff; }

/* ---- Mobile toggle (hidden on desktop) ------------------------------ */
.nav-toggle { display: none; width: 28px; height: 22px; position: relative; }
.nav-toggle span {
  position: absolute;
  left: 0;
  width: 100%;
  height: 2px;
  background: var(--header-text);
  transition: transform var(--transition), opacity var(--transition), background var(--transition);
}
.nav-toggle span:nth-child(1) { top: 0; }
.nav-toggle span:nth-child(2) { top: 50%; transform: translateY(-50%); }
.nav-toggle span:nth-child(3) { bottom: 0; }

/* ---- Responsive ----------------------------------------------------- */
@media (max-width: 768px) {
  .nav-toggle { display: block; }

  .site-nav {
    position: fixed;
    inset: var(--header-height) 0 auto 0;
    background: var(--color-black);
    padding: var(--space-md) var(--gutter);
    transform: translateY(-120%);
    transition: transform var(--transition);
  }
  .site-nav.is-open { transform: translateY(0); }
  .site-nav__list { flex-direction: column; gap: var(--space-sm); }
  .site-nav a { color: var(--color-white); font-size: 1.25rem; }

  .nav-toggle[aria-expanded="true"] span:nth-child(1) { top: 50%; transform: translateY(-50%) rotate(45deg); }
  .nav-toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
  .nav-toggle[aria-expanded="true"] span:nth-child(3) { bottom: 50%; transform: translateY(50%) rotate(-45deg); }
}