/* ===== reset ===== */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
}

@media (prefers-reduced-motion: no-preference) {
  html {
    scroll-behavior: smooth;
  }
}

body,
h1,
h2,
h3,
h4,
p,
figure,
blockquote,
ul,
ol {
  margin: 0;
}

ul,
ol {
  padding: 0;
  list-style: none;
}

img,
svg,
video {
  display: block;
  max-width: 100%;
}

a {
  color: inherit;
  text-decoration: none;
}

button,
input,
select,
textarea {
  font: inherit;
  color: inherit;
}

button {
  background: none;
  border: 0;
  padding: 0;
  cursor: pointer;
}

/* ===== variables ===== */
:root {
  --ink: #061826;
  --ink-2: #0c2638;
  --ink-3: #12384f;
  --cyan: #2ef2d0;
  --cyan-soft: rgba(46, 242, 208, 0.14);
  --teal: #0fa98f;
  --coral: #ff6b4a;
  --coral-deep: #c94b32;
  --gold: #d8b36a;
  --gold-soft: rgba(216, 179, 106, 0.28);
  --mist: #e9f2f6;
  --slate: #8fa9b8;
  --violet: #7c5cff;
  --black: #020b12;

  --shell: 1280px;
  --gutter: clamp(1rem, 4vw, 3rem);
  --header-h: 72px;

  --radius-s: 8px;
  --radius-m: 14px;
  --radius-l: 26px;

  --font-sans: "Noto Sans SC", "Source Han Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-mono: "JetBrains Mono", "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

/* ===== base typography ===== */
body {
  min-height: 100vh;
  background-color: var(--ink);
  background-image:
    radial-gradient(900px 620px at 92% -6%, rgba(46, 242, 208, 0.11), transparent 62%),
    radial-gradient(760px 520px at -8% 20%, rgba(124, 92, 255, 0.13), transparent 60%),
    radial-gradient(820px 560px at 82% 110%, rgba(255, 107, 74, 0.09), transparent 60%);
  background-attachment: fixed;
  color: var(--mist);
  font-family: var(--font-sans);
  font-size: 16px;
  font-weight: 400;
  line-height: 1.75;
  letter-spacing: 0.005em;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

@media (min-width: 768px) {
  body {
    font-size: 17px;
  }
}

h1,
h2,
h3,
h4 {
  font-weight: 900;
  line-height: 1.15;
  letter-spacing: -0.03em;
  color: var(--mist);
}

h1 {
  font-size: clamp(2.25rem, 6vw, 4.5rem);
}

h2 {
  font-size: clamp(1.5rem, 3.4vw, 2.5rem);
}

h3 {
  font-size: clamp(1.125rem, 2vw, 1.5rem);
}

p {
  max-width: 68ch;
}

strong {
  font-weight: 700;
  color: var(--mist);
}

code,
kbd,
samp {
  font-family: var(--font-mono);
  font-size: 0.9em;
  color: var(--gold);
}

::selection {
  background: rgba(46, 242, 208, 0.28);
  color: var(--mist);
}

:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 3px;
  border-radius: 4px;
}

#main-content {
  display: block;
  scroll-margin-top: calc(var(--header-h) + 12px);
}

/* ===== utilities ===== */
.shell {
  width: 100%;
  max-width: var(--shell);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

/* ===== skip link ===== */
.skip-link {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 130;
  display: inline-block;
  padding: 0.7rem 1.25rem;
  border-radius: 0 0 var(--radius-s) 0;
  background: var(--cyan);
  color: var(--ink);
  font-size: 0.875rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  transform: translateY(-130%);
  transition: transform 0.24s var(--ease);
}

.skip-link:focus,
.skip-link:focus-visible {
  transform: translateY(0);
  outline-offset: 2px;
}

/* ===== buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  min-height: 44px;
  padding: 0.7rem 1.4rem;
  border: 1px solid transparent;
  border-radius: 999px;
  font-family: var(--font-sans);
  font-size: 0.9375rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  line-height: 1.2;
  text-align: center;
  cursor: pointer;
  transition:
    transform 0.2s var(--ease),
    background-color 0.2s var(--ease),
    border-color 0.2s var(--ease),
    color 0.2s var(--ease),
    box-shadow 0.2s var(--ease);
}

.btn--coral {
  background: var(--coral);
  color: #1b0703;
  box-shadow: 0 12px 28px -16px rgba(255, 107, 74, 0.95);
}

.btn--coral:hover {
  background: #ff8a70;
  transform: translateY(-1px);
  box-shadow: 0 18px 32px -16px rgba(255, 107, 74, 1);
}

.btn--coral:active {
  background: var(--coral-deep);
  color: var(--mist);
  transform: translateY(0);
}

.btn--ghost {
  background: transparent;
  border-color: var(--gold-soft);
  color: var(--mist);
}

.btn--ghost:hover {
  border-color: var(--cyan);
  color: var(--cyan);
  background: var(--cyan-soft);
}

.btn--sm {
  min-height: 44px;
  padding: 0.42rem 1.05rem;
  font-size: 0.875rem;
}

/* ===== tags ===== */
.tag {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.2rem 0.6rem;
  border: 1px solid var(--gold-soft);
  border-radius: 999px;
  background: rgba(216, 179, 106, 0.06);
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  font-weight: 500;
  letter-spacing: 0.1em;
  color: var(--gold);
  white-space: nowrap;
}

.tag--cyan {
  border-color: rgba(46, 242, 208, 0.35);
  background: rgba(46, 242, 208, 0.08);
  color: var(--cyan);
}

.tag--coral {
  border-color: rgba(255, 107, 74, 0.4);
  background: rgba(255, 107, 74, 0.08);
  color: var(--coral);
}

/* ===== breadcrumbs ===== */
.crumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  font-weight: 500;
  letter-spacing: 0.1em;
  color: var(--slate);
}

.crumbs__item {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
}

.crumbs__link {
  color: var(--slate);
  transition: color 0.2s var(--ease);
}

.crumbs__link:hover {
  color: var(--cyan);
}

.crumbs__sep {
  color: var(--gold);
  opacity: 0.6;
}

.crumbs__current {
  color: var(--mist);
}

/* ===== media frame ===== */
.media-frame {
  position: relative;
  display: block;
  width: 100%;
  aspect-ratio: 16 / 10;
  overflow: hidden;
  border: 1px solid var(--gold-soft);
  border-radius: var(--radius-m);
  background-color: var(--ink-2);
  background-image:
    radial-gradient(120% 120% at 0% 0%, rgba(46, 242, 208, 0.14), transparent 55%),
    radial-gradient(110% 110% at 100% 100%, rgba(255, 107, 74, 0.1), transparent 58%),
    linear-gradient(160deg, var(--ink-2), var(--black));
}

.media-frame::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(216, 179, 106, 0.12) 1px, transparent 1px),
    linear-gradient(90deg, rgba(216, 179, 106, 0.12) 1px, transparent 1px);
  background-size: 32px 32px;
  -webkit-mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.6), transparent 78%);
  mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.6), transparent 78%);
}

.media-frame img,
.media-frame svg {
  position: absolute;
  inset: 0;
  z-index: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.media-frame--wide {
  aspect-ratio: 21 / 9;
}

.media-frame--tall {
  aspect-ratio: 4 / 5;
}

.media-frame--square {
  aspect-ratio: 1 / 1;
}

.media-frame__code {
  position: absolute;
  left: 0.85rem;
  bottom: 0.85rem;
  z-index: 2;
  padding: 0.2rem 0.5rem;
  border: 1px solid var(--gold-soft);
  border-radius: 4px;
  background: rgba(2, 11, 18, 0.78);
  font-family: var(--font-mono);
  font-size: 0.625rem;
  font-weight: 500;
  letter-spacing: 0.14em;
  color: var(--gold);
}

/* ===== reveal protocol ===== */
html[data-js="true"] [data-reveal] {
  opacity: 0;
  transform: translateY(18px);
  transition:
    opacity 0.6s var(--ease),
    transform 0.6s var(--ease);
}

html[data-js="true"] [data-reveal][data-revealed="true"] {
  opacity: 1;
  transform: none;
}

/* ===== site header ===== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: transparent;
  border-bottom: 1px solid transparent;
  transition:
    background-color 0.35s var(--ease),
    border-color 0.35s var(--ease),
    box-shadow 0.35s var(--ease);
}

.site-header::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background: linear-gradient(180deg, rgba(2, 11, 18, 0.84) 0%, rgba(2, 11, 18, 0.38) 58%, rgba(2, 11, 18, 0) 100%);
  opacity: 1;
  transition: opacity 0.35s var(--ease);
}

.site-header[data-stuck="true"] {
  background: rgba(6, 24, 38, 0.97);
  border-bottom-color: var(--gold-soft);
  box-shadow: 0 22px 46px -30px rgba(0, 0, 0, 0.95);
}

.site-header[data-stuck="true"]::before {
  opacity: 0;
}

.read-progress {
  position: absolute;
  inset: 0 0 auto 0;
  height: 2px;
  overflow: hidden;
  background: rgba(46, 242, 208, 0.1);
}

.read-progress__bar {
  display: block;
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--cyan) 0%, var(--violet) 55%, var(--coral) 100%);
  box-shadow: 0 0 12px rgba(46, 242, 208, 0.55);
  transition: width 0.1s linear;
}

.header-shell {
  display: flex;
  align-items: center;
  gap: clamp(0.75rem, 2vw, 2rem);
  width: 100%;
  max-width: var(--shell);
  min-height: var(--header-h);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

/* brand */
.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.7rem;
  flex: 0 0 auto;
  padding-block: 0.4rem;
}

.brand__rail {
  flex: 0 0 auto;
  width: 3px;
  height: 34px;
  border-radius: 2px;
  background: linear-gradient(180deg, var(--cyan) 0%, var(--teal) 52%, var(--coral) 100%);
  box-shadow: 0 0 14px rgba(46, 242, 208, 0.5);
}

.brand__body {
  display: flex;
  flex-direction: column;
  gap: 3px;
  line-height: 1;
}

.brand__name {
  font-size: 1.0625rem;
  font-weight: 900;
  letter-spacing: -0.02em;
  color: var(--mist);
}

.brand__meta {
  font-family: var(--font-mono);
  font-size: 0.5625rem;
  font-weight: 500;
  letter-spacing: 0.18em;
  color: var(--gold);
  text-transform: uppercase;
  white-space: nowrap;
}

/* nav toggle */
.nav-toggle {
  display: none;
  align-items: center;
  gap: 0.55rem;
  min-height: 44px;
  margin-left: auto;
  padding: 0.35rem 0.9rem;
  border: 1px solid var(--gold-soft);
  border-radius: 999px;
  background: rgba(18, 56, 79, 0.4);
  color: var(--mist);
  transition:
    border-color 0.25s var(--ease),
    color 0.25s var(--ease),
    background-color 0.25s var(--ease);
}

.nav-toggle:hover {
  border-color: var(--cyan);
  color: var(--cyan);
  background: var(--cyan-soft);
}

.nav-toggle__bars {
  display: inline-flex;
  flex-direction: column;
  gap: 4px;
  width: 18px;
}

.nav-toggle__bars i {
  display: block;
  height: 2px;
  border-radius: 2px;
  background: currentColor;
  transition:
    transform 0.25s var(--ease),
    opacity 0.2s var(--ease);
}

.nav-toggle__label {
  font-size: 0.8125rem;
  font-weight: 700;
  letter-spacing: 0.12em;
}

.site-header[data-open] .nav-toggle {
  border-color: var(--coral);
  color: var(--coral);
  background: rgba(255, 107, 74, 0.12);
}

.site-header[data-open] .nav-toggle__bars i:nth-child(1) {
  transform: translateY(6px) rotate(45deg);
}

.site-header[data-open] .nav-toggle__bars i:nth-child(2) {
  opacity: 0;
}

.site-header[data-open] .nav-toggle__bars i:nth-child(3) {
  transform: translateY(-6px) rotate(-45deg);
}

/* desktop nav */
.site-nav {
  display: flex;
  align-items: center;
  gap: clamp(0.5rem, 1.6vw, 1.5rem);
  margin-left: auto;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: clamp(0.15rem, 1vw, 1rem);
}

.nav-item {
  display: flex;
}

.nav-link {
  position: relative;
  display: inline-flex;
  align-items: baseline;
  gap: 0.4rem;
  min-height: 44px;
  padding: 0.55rem 0.5rem;
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--slate);
  transition: color 0.22s var(--ease);
}

.nav-link:hover,
.nav-link:focus-visible {
  color: var(--mist);
}

.nav-num {
  font-family: var(--font-mono);
  font-size: 0.5625rem;
  font-weight: 500;
  letter-spacing: 0.1em;
  color: var(--gold);
  opacity: 0.85;
}

.nav-link::after {
  content: "";
  position: absolute;
  left: 0.5rem;
  right: 0.5rem;
  bottom: 0.2rem;
  height: 1px;
  background: var(--cyan);
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform 0.3s var(--ease);
}

.nav-link:hover::after,
.nav-link:focus-visible::after {
  transform: scaleX(1);
}

.nav-link[aria-current="page"] {
  color: var(--cyan);
  font-weight: 700;
}

.nav-link[aria-current="page"]::after {
  transform: scaleX(1);
  height: 2px;
  background: var(--coral);
}

.nav-link[aria-current="page"] .nav-num {
  color: var(--cyan);
  opacity: 1;
}

.nav-cta {
  display: flex;
  align-items: center;
  margin-left: 0.35rem;
}

/* ===== site footer ===== */
.site-footer {
  position: relative;
  margin-top: clamp(4rem, 10vw, 8rem);
  background: var(--black);
  color: var(--slate);
}

.site-footer::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 1px;
  background: linear-gradient(
    90deg,
    transparent 0%,
    rgba(46, 242, 208, 0.6) 22%,
    rgba(216, 179, 106, 0.55) 50%,
    rgba(255, 107, 74, 0.6) 78%,
    transparent 100%
  );
}

.footer-shell {
  width: 100%;
  max-width: var(--shell);
  margin-inline: auto;
  padding: clamp(2.5rem, 6vw, 4.5rem) var(--gutter) 1.75rem;
}

.footer-top {
  display: grid;
  grid-template-columns: 1.3fr 1fr 1fr 1.15fr;
  gap: clamp(1.75rem, 4vw, 3rem);
}

.footer-brand {
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.footer-brand__name {
  font-size: 1.125rem;
  font-weight: 900;
  letter-spacing: -0.02em;
  color: var(--mist);
}

.footer-brand__code {
  margin-top: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.5625rem;
  font-weight: 500;
  letter-spacing: 0.2em;
  color: var(--gold);
  text-transform: uppercase;
}

.footer-brand__note {
  margin-top: 1rem;
  max-width: 30ch;
  font-size: 0.875rem;
  line-height: 1.8;
  color: var(--slate);
}

.footer-col {
  min-width: 0;
}

.footer-col__title {
  position: relative;
  padding-left: 0.85rem;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.18em;
  line-height: 1.4;
  color: var(--mist);
}

.footer-col__title::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  width: 3px;
  height: 15px;
  margin-top: -7.5px;
  border-radius: 1px;
  background: linear-gradient(180deg, var(--cyan), var(--coral));
}

.footer-links {
  display: flex;
  flex-direction: column;
  margin-top: 0.85rem;
}

.footer-link {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  padding-left: 0;
  font-size: 0.875rem;
  color: var(--slate);
  transition:
    color 0.2s var(--ease),
    padding-left 0.2s var(--ease);
}

.footer-link:hover,
.footer-link:focus-visible {
  color: var(--cyan);
  padding-left: 0.35rem;
}

.contact-list {
  display: flex;
  flex-direction: column;
  gap: 0.7rem;
  margin-top: 1.1rem;
}

.contact-row {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.3rem 0.6rem;
  font-size: 0.875rem;
}

.contact-key {
  flex: 0 0 auto;
  padding: 0.08rem 0.4rem;
  border: 1px solid var(--gold-soft);
  border-radius: 4px;
  font-family: var(--font-mono);
  font-size: 0.5625rem;
  font-weight: 500;
  letter-spacing: 0.14em;
  color: var(--gold);
  line-height: 1.6;
}

.contact-value {
  color: var(--mist);
  word-break: break-word;
}

.footer-contact-note {
  margin-top: 1.1rem;
  max-width: 36ch;
  font-size: 0.75rem;
  line-height: 1.8;
  color: rgba(143, 169, 184, 0.85);
}

.footer-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem 1.75rem;
  margin-top: clamp(2rem, 4vw, 3rem);
  padding-top: 1.25rem;
  border-top: 1px solid rgba(216, 179, 106, 0.16);
  font-family: var(--font-mono);
  font-size: 0.625rem;
  font-weight: 500;
  letter-spacing: 0.1em;
  color: rgba(143, 169, 184, 0.9);
}

.footer-meta__item {
  max-width: none;
}

.footer-meta__item--wide {
  flex-basis: 100%;
  font-size: 0.625rem;
  letter-spacing: 0.08em;
  color: rgba(143, 169, 184, 0.68);
}

/* ===== responsive ===== */
@media (max-width: 1000px) {
  :root {
    --header-h: 64px;
  }

  html[data-nav-open="true"] {
    overflow: hidden;
  }

  .nav-toggle {
    display: inline-flex;
  }

  .site-nav {
    position: fixed;
    top: var(--header-h);
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 95;
    display: flex;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    margin-left: 0;
    padding: clamp(1rem, 4vw, 1.75rem) var(--gutter) 2.5rem;
    overflow-y: auto;
    background-color: var(--ink);
    background-image:
      radial-gradient(120% 80% at 100% 0%, rgba(255, 107, 74, 0.16), transparent 60%),
      radial-gradient(90% 70% at 0% 100%, rgba(46, 242, 208, 0.14), transparent 62%),
      radial-gradient(80% 60% at 50% 30%, rgba(124, 92, 255, 0.1), transparent 65%);
    border-top: 1px solid var(--gold-soft);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition:
      opacity 0.28s var(--ease),
      transform 0.28s var(--ease),
      visibility 0.28s var(--ease);
  }

  .site-header[data-open] .site-nav {
    opacity: 1;
    visibility: visible;
    transform: none;
  }

  .nav-list {
    flex-direction: column;
    gap: 0;
  }

  .nav-item {
    display: block;
    border-bottom: 1px solid rgba(216, 179, 106, 0.16);
  }

  .nav-link {
    width: 100%;
    padding: 1rem 0.25rem;
    font-size: 1.0625rem;
    gap: 0.75rem;
  }

  .nav-link::after {
    display: none;
  }

  .nav-link[aria-current="page"] {
    box-shadow: inset 3px 0 0 var(--coral);
    padding-left: 0.75rem;
  }

  .nav-num {
    font-size: 0.6875rem;
  }

  .nav-cta {
    margin-top: 1.5rem;
    margin-left: 0;
  }

  .nav-cta .btn {
    width: 100%;
  }

  .footer-top {
    grid-template-columns: 1fr 1fr;
  }

  .footer-brand {
    grid-column: 1 / -1;
  }
}

@media (max-width: 640px) {
  .brand__meta {
    display: none;
  }

  .brand__name {
    font-size: 0.9375rem;
  }

  .footer-top {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

  .footer-meta {
    justify-content: flex-start;
  }

  .media-frame {
    aspect-ratio: 4 / 3;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }

  html[data-js="true"] [data-reveal] {
    opacity: 1;
    transform: none;
  }

  .read-progress__bar {
    transition: none;
  }
}