/* —— Header —— */
.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  padding-top: env(safe-area-inset-top, 0px);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(12px) saturate(1.1);
  -webkit-backdrop-filter: blur(12px) saturate(1.1);
  border-bottom: 1px solid transparent;
}

.site-header.is-scrolled,
.site-header.is-nav-open {
  border-bottom-color: var(--line);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
  gap: 16px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 9px;
  color: var(--ink);
  text-decoration: none;
  font-weight: 600;
  font-size: 0.95rem;
  letter-spacing: -0.01em;
}

.logo:hover {
  color: var(--ink);
}

.logo img {
  width: 26px;
  height: 26px;
  object-fit: contain;
}

.header-right {
  display: flex;
  align-items: center;
  gap: 8px;
}

.header-nav {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-right: 4px;
}

.header-nav a {
  color: var(--muted);
  text-decoration: none;
  font-size: 0.875rem;
  padding: 6px 10px;
  border-radius: 8px;
}

.header-nav a:hover {
  color: var(--ink);
  background: var(--hover-fill);
}

.header-nav a.is-active {
  color: var(--ink);
  background: var(--hover-fill);
}

/* GitHub lives in the header chip on desktop; in the hamburger list on small screens. */
.header-nav__github {
  display: none;
}

/* Mobile menu toggle — same chip family as lang / GitHub */
.nav-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  margin: 0;
  width: 36px;
  height: 36px;
  padding: 0;
  border-radius: 9999px;
  border: 1px solid var(--color-theme-border-01);
  background-color: var(--color-theme-card-03-hex);
  color: var(--color-theme-text);
  cursor: pointer;
  flex-shrink: 0;
  transition:
    background-color var(--cursor-duration, 0.14s) var(--cursor-ease, cubic-bezier(0.25, 1, 0.5, 1)),
    border-color var(--cursor-duration, 0.14s) var(--cursor-ease, cubic-bezier(0.25, 1, 0.5, 1));
  -webkit-tap-highlight-color: transparent;
}

.nav-toggle:hover {
  background-color: var(--color-theme-card-04-hex);
}

.nav-toggle:focus-visible {
  outline: 2px solid var(--color-theme-fg);
  outline-offset: 0.3ch;
}

.nav-toggle__icon {
  display: block;
  width: 16px;
  height: 16px;
  pointer-events: none;
}

.nav-toggle__icon--close {
  display: none;
}

.site-header.is-nav-open .nav-toggle__icon--open {
  display: none;
}

.site-header.is-nav-open .nav-toggle__icon--close {
  display: block;
}

.nav-backdrop {
  display: none;
}

/* =========================================================
   Theme + language controls — migrated from huiai-product
   (Cursor marketing theme-pill + prefs__lang)
   ========================================================= */

.prefs {
  --cursor-g: calc(10rem / 16); /* 10px @ 16 */
  --cursor-v: 1.4rem;
  --cursor-duration: 0.14s;
  --cursor-ease: cubic-bezier(0.25, 1, 0.5, 1);
  --cursor-btn-pad: 0.4em 0.75em 0.42em;
  --cursor-radius-xs: 4px;
  display: inline-flex;
  align-items: center;
  gap: calc(var(--cursor-g) * 1.5); /* 15px */
}

/* Theme pill: System / Light / Dark */
.theme-pill {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2px;
  border-radius: 9999px;
  background-color: var(--color-theme-card-03-hex);
  text-align: center;
  font-family: system-ui, -apple-system, "Helvetica Neue", Helvetica, Arial, sans-serif;
  font-size: 0.875rem;
  font-weight: 400;
  line-height: 1.5;
  letter-spacing: 0.01em;
  color: var(--color-theme-text);
}

.theme-pill__thumb {
  position: absolute;
  top: 2px;
  bottom: 2px;
  left: 2px;
  width: 0;
  border-radius: 9999px;
  background-color: var(--color-theme-fg-10);
  transition-property: left, width, opacity;
  transition-duration: var(--cursor-duration);
  transition-timing-function: var(--cursor-ease);
  pointer-events: none;
  opacity: 0;
  z-index: 0;
}

.theme-pill__thumb.is-ready {
  opacity: 1;
}

.theme-pill__btn {
  position: relative;
  z-index: 1;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  margin: 0;
  padding: var(--cursor-btn-pad);
  border: 0;
  border-radius: 9999px;
  background: transparent;
  color: var(--color-theme-text-sec);
  font: inherit;
  font-size: inherit;
  font-weight: 400;
  line-height: 1;
  letter-spacing: inherit;
  cursor: pointer;
  outline: none;
  -webkit-tap-highlight-color: transparent;
}

.theme-pill__btn:hover {
  color: var(--color-theme-text);
}

.theme-pill__btn[aria-pressed="true"] {
  color: var(--color-theme-text);
}

.theme-pill__btn:focus-visible {
  outline: 2px solid var(--color-theme-fg);
  outline-offset: 0.3ch;
}

.theme-pill__icon {
  display: block;
  width: 14px;
  height: 14px;
  flex-shrink: 0;
  pointer-events: none;
}

/* Language: globe + label flyout (no chevron) */
.prefs__lang {
  position: relative;
  display: inline-flex;
  align-items: center;
}

.prefs__lang-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: calc(var(--cursor-g) * 0.5); /* 5px */
  margin: 0;
  padding: var(--cursor-btn-pad);
  border-radius: 9999px;
  border: 1px solid var(--color-theme-border-01);
  background-color: var(--color-theme-card-03-hex);
  color: var(--color-theme-text);
  font: inherit;
  font-size: 0.875rem;
  font-weight: 400;
  line-height: 1;
  letter-spacing: 0.01em;
  cursor: pointer;
  transition:
    background-color var(--cursor-duration) var(--cursor-ease),
    border-color var(--cursor-duration) var(--cursor-ease),
    color var(--cursor-duration) var(--cursor-ease);
  -webkit-tap-highlight-color: transparent;
}

.prefs__lang-btn:hover {
  background-color: var(--color-theme-card-04-hex);
  border-color: var(--color-theme-border-01);
  color: var(--color-theme-text);
}

.prefs__lang-btn[aria-expanded="true"] {
  background-color: var(--color-theme-card-04-hex);
}

.prefs__lang-btn:active {
  background-color: var(--color-theme-card-03-hex);
  border-color: var(--color-theme-border-01);
}

.prefs__lang-btn:focus-visible {
  outline: 2px solid var(--color-theme-fg);
  outline-offset: 0.3ch;
}

.prefs__lang-globe {
  display: block;
  width: 14px;
  height: 14px;
  flex-shrink: 0;
  pointer-events: none;
}

.prefs__lang-label {
  display: none;
}

.prefs--header .prefs__lang-btn {
  padding-inline: 0.7em;
}

/* GitHub — same chip as language control */
.prefs__github {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: calc(var(--cursor-g) * 0.5); /* 5px */
  margin: 0;
  padding: var(--cursor-btn-pad);
  border-radius: 9999px;
  border: 1px solid var(--color-theme-border-01);
  background-color: var(--color-theme-card-03-hex);
  color: var(--color-theme-text);
  font: inherit;
  font-size: 0.875rem;
  font-weight: 400;
  line-height: 1;
  letter-spacing: 0.01em;
  text-decoration: none;
  cursor: pointer;
  transition:
    background-color var(--cursor-duration) var(--cursor-ease),
    border-color var(--cursor-duration) var(--cursor-ease),
    color var(--cursor-duration) var(--cursor-ease);
  -webkit-tap-highlight-color: transparent;
}

.prefs__github:hover {
  background-color: var(--color-theme-card-04-hex);
  border-color: var(--color-theme-border-01);
  color: var(--color-theme-text);
  text-decoration: none;
}

.prefs__github:active {
  background-color: var(--color-theme-card-03-hex);
  border-color: var(--color-theme-border-01);
}

.prefs__github:focus-visible {
  outline: 2px solid var(--color-theme-fg);
  outline-offset: 0.3ch;
}

.prefs__github-icon {
  display: block;
  width: 14px;
  height: 14px;
  flex-shrink: 0;
  pointer-events: none;
}

.prefs__github-label {
  display: none;
}

.prefs--header .prefs__github {
  padding-inline: 0.7em;
}

.prefs__lang-flyout {
  position: absolute;
  top: auto;
  bottom: 100%;
  left: auto;
  right: 0;
  z-index: 50;
  margin-bottom: calc(var(--cursor-v) * 6 / 12);
  padding-top: calc(var(--cursor-v) * 3 / 12);
  min-width: 10rem;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transform: translateY(0.4rem);
  transition:
    opacity var(--cursor-duration) var(--cursor-ease),
    transform var(--cursor-duration) var(--cursor-ease),
    visibility 0s linear var(--cursor-duration);
}

.prefs__lang-flyout.is-open {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transform: translateY(0);
  transition-delay: 0s;
}

/* Header: open downward */
.prefs--header .prefs__lang-flyout {
  top: 100%;
  bottom: auto;
  margin-bottom: 0;
  margin-top: calc(var(--cursor-v) * 3 / 12);
  padding-top: calc(var(--cursor-v) * 3 / 12);
  transform: translateY(-0.4rem);
}

.prefs--header .prefs__lang-flyout.is-open {
  transform: translateY(0);
}

.prefs__lang-card {
  position: relative;
  margin: 0;
  padding: calc(var(--cursor-g) * 0.75) 0;
  min-width: 10rem;
  border-radius: var(--cursor-radius-xs);
  background-color: var(--color-theme-card-02-hex);
  box-shadow: 0 0 1rem #00000005, 0 0 0.5rem #00000002;
  font-size: 0.875rem;
  font-weight: 400;
  line-height: 1.5;
  letter-spacing: 0.01em;
  color: var(--color-theme-text);
}

html[data-theme="dark"] .prefs__lang-card {
  box-shadow: 0 0 1rem #00000040, 0 0 0.5rem #00000026;
}

.prefs__lang-card::before {
  content: "";
  pointer-events: none;
  position: absolute;
  inset: 0;
  z-index: 1;
  border-radius: var(--cursor-radius-xs);
  border: 1px solid var(--color-theme-border-01-5);
}

.prefs__lang-menu {
  position: relative;
  z-index: 2;
  margin: 0;
  padding: 0;
  list-style: none;
}

.prefs__lang-menu button {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  gap: 0;
  margin: 0;
  padding: calc(var(--cursor-v) * 2.5 / 12) calc(var(--cursor-g) * 1.5);
  border: 0;
  border-radius: 0;
  background: transparent;
  color: var(--color-theme-text);
  font: inherit;
  font-size: 0.875rem;
  font-weight: 400;
  line-height: 1.5;
  letter-spacing: 0.01em;
  text-align: left;
  cursor: pointer;
  transition: color var(--cursor-duration) var(--cursor-ease);
}

.prefs__lang-menu button:hover {
  color: color-mix(in oklab, var(--color-theme-fg) 75%, transparent);
  background: transparent;
}

.prefs__lang-menu button:focus-visible {
  outline: 2px solid var(--color-theme-fg);
  outline-offset: 0.3ch;
}

.prefs__lang-menu button[aria-selected="true"] {
  color: var(--color-theme-text);
  font-weight: 400;
  background: transparent;
}

.prefs__lang-menu button[aria-selected="true"]::after {
  content: "";
  flex: none;
  display: block;
  width: 12px;
  height: 12px;
  margin-left: 0.5rem;
  background-color: currentColor;
  -webkit-mask: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16'%3E%3Cpath fill='black' d='M1 8.77Q1 8.33 1.44 7.96Q1.71 7.72 2.1 7.72Q2.61 7.72 3 8.26L5.94 12.17L12.92 2.08Q13.34 1.49 13.85 1.49Q14.19 1.49 14.54 1.73Q15 2.1 15 2.56Q15 2.93 14.68 3.39L7.38 13.66Q6.79 14.51 5.91 14.51Q5.08 14.51 4.37 13.66L1.32 9.58Q1 9.16 1 8.77Z'/%3E%3C/svg%3E")
    center / contain no-repeat;
  mask: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16'%3E%3Cpath fill='black' d='M1 8.77Q1 8.33 1.44 7.96Q1.71 7.72 2.1 7.72Q2.61 7.72 3 8.26L5.94 12.17L12.92 2.08Q13.34 1.49 13.85 1.49Q14.19 1.49 14.54 1.73Q15 2.1 15 2.56Q15 2.93 14.68 3.39L7.38 13.66Q6.79 14.51 5.91 14.51Q5.08 14.51 4.37 13.66L1.32 9.58Q1 9.16 1 8.77Z'/%3E%3C/svg%3E")
    center / contain no-repeat;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  border-radius: var(--vh-r-btn);
  padding: 9px 15px;
  font: inherit;
  font-size: 0.875rem;
  font-weight: 600;
  line-height: 1;
  border: 1px solid transparent;
  cursor: pointer;
  text-decoration: none;
  transition:
    background 0.15s ease,
    border-color 0.15s ease,
    color 0.15s ease,
    transform 0.15s ease;
}

.btn:hover {
  text-decoration: none;
}

/* Primary CTA — 亮橙实底 */
.btn-primary {
  color: var(--btn-primary-fg);
  background: var(--btn-primary-bg);
  border-color: var(--btn-primary-bg);
}

.btn-primary:hover {
  color: var(--btn-primary-fg);
  background: var(--btn-primary-bg-hover);
  border-color: var(--btn-primary-bg-hover);
  transform: translateY(-2px);
}

.btn-primary:active {
  transform: translateY(0);
}

/* Secondary — 描边线，无玻璃 */
.btn-ghost {
  color: var(--ink);
  background: transparent;
  border-color: var(--vh-line-strong);
}

.btn-ghost:hover {
  color: var(--ink);
  background: var(--vh-paper-warm);
  border-color: var(--vh-line-strong);
  transform: translateY(-2px);
}

.btn-lg {
  height: 44px;
  padding: 0 22px;
  font-size: 0.95rem;
  border-radius: var(--vh-r-btn);
  line-height: 1;
}

.btn-icon {
  flex-shrink: 0;
  display: block;
}

.btn-lg .btn-icon {
  width: 17px;
  height: 17px;
}

.btn-arrow {
  opacity: 0.7;
  transition: transform 0.14s ease, opacity 0.14s ease;
  font-weight: 500;
}

.btn-primary:hover .btn-arrow {
  transform: translateX(2px);
  opacity: 1;
}

.btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}