.page-contact {
  --co-ink: #0B1B33;
  --co-paper: #FFFFFF;
  --co-line: rgba(11, 27, 51, 0.16);
  --co-muted: rgba(11, 27, 51, 0.64);
  --co-hard: 7px 7px 0 0 rgba(11, 27, 51, 0.9);
  --co-hard-cyan: 8px 8px 0 0 rgba(22, 224, 200, 0.85);
}

.co-sep {
  margin: 0 8px;
  color: var(--co-muted);
}

.co-section-title {
  margin-top: 14px;
  max-width: 22ch;
}

/* ---------- 首屏 ---------- */
.co-hero {
  position: relative;
  overflow: hidden;
  padding-top: clamp(96px, 13vw, 156px);
  padding-bottom: clamp(46px, 6vw, 76px);
}

.co-hero::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 7px;
  background-image: repeating-linear-gradient(90deg, var(--co-line) 0 2px, transparent 2px 20px);
  pointer-events: none;
}

.co-hero__grid {
  align-items: end;
  row-gap: 40px;
  margin-top: clamp(20px, 3vw, 34px);
}

.co-hero__title {
  margin: 16px 0 0;
  line-height: 1.04;
}

.co-hero__mark {
  box-shadow: inset 0 -0.16em 0 0 rgba(22, 224, 200, 0.72);
}

.co-hero__lede {
  margin-top: 24px;
  max-width: 62ch;
}

.co-hero__aside {
  border-top: 3px solid var(--yb-orange);
  border-bottom: 2px solid var(--co-line);
  padding: 22px 0 20px;
}

.co-hero__aside-num {
  margin: 0;
  font-family: var(--yb-font-mono);
  font-size: clamp(46px, 6.4vw, 82px);
  font-weight: 700;
  line-height: 0.94;
  letter-spacing: -0.03em;
  color: var(--co-ink);
}

.co-hero__aside-unit {
  margin: 8px 0 0;
  font-family: var(--yb-font-mono);
  font-size: 14px;
  letter-spacing: 0.18em;
  color: var(--yb-orange);
}

.co-hero__aside-text {
  margin: 14px 0 0;
  font-size: 14px;
  line-height: 1.75;
  color: var(--co-muted);
}

/* ---------- 合作方向 ---------- */
.co-direction__figure {
  margin: clamp(26px, 4vw, 44px) 0 clamp(32px, 4.5vw, 54px);
}

.co-direction__grid {
  align-items: start;
  row-gap: 40px;
}

.co-direction__note {
  margin: clamp(28px, 4vw, 42px) 0 0;
  padding-top: 18px;
  border-top: 2px dashed var(--co-line);
  font-size: 14px;
  line-height: 1.8;
  color: var(--co-muted);
}

.co-direction__note a,
.co-flow__note a {
  color: var(--co-ink);
  text-decoration: underline;
  text-decoration-color: var(--yb-cyan);
  text-decoration-thickness: 2px;
  text-underline-offset: 4px;
  transition: color 0.2s var(--yb-ease);
}

.co-direction__note a:hover,
.co-flow__note a:hover,
.co-direction__note a:focus-visible,
.co-flow__note a:focus-visible {
  color: var(--yb-orange);
}

/* 联系清单 */
.co-rail__head {
  margin: 0 0 14px;
  font-family: var(--yb-font-mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  color: var(--co-muted);
}

.co-rail__list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 12px;
}

.co-rail__item {
  display: block;
  padding: 15px 17px;
  border: 2px solid var(--co-line);
  background: var(--co-paper);
  text-decoration: none;
  color: inherit;
  transition: border-color 0.22s var(--yb-ease),
    transform 0.22s var(--yb-ease),
    box-shadow 0.22s var(--yb-ease);
}

.co-rail__item:hover,
.co-rail__item:focus-visible {
  border-color: var(--yb-cyan);
  transform: translateY(-4px);
  box-shadow: var(--co-hard-cyan);
  outline: 3px solid var(--yb-cyan);
  outline-offset: 2px;
}

.co-rail__label {
  display: block;
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--co-muted);
}

.co-rail__value {
  display: block;
  margin-top: 7px;
  font-family: var(--yb-font-mono);
  font-size: clamp(14px, 1.6vw, 17px);
  font-weight: 600;
  color: var(--co-ink);
  word-break: break-all;
}

.co-rail__note {
  margin: 14px 0 0;
  font-size: 13px;
  line-height: 1.7;
  color: var(--co-muted);
}

/* 合作方向卡片 */
.co-cards {
  display: grid;
  gap: 26px;
}

.co-card {
  border: 3px solid var(--co-ink);
  background: var(--co-paper);
  box-shadow: var(--co-hard);
  padding: clamp(20px, 2.8vw, 30px);
  transition: transform 0.24s var(--yb-ease), box-shadow 0.24s var(--yb-ease);
}

.co-card:hover,
.co-card:focus-within {
  transform: translateY(-4px);
  box-shadow: 9px 10px 0 0 rgba(22, 224, 200, 0.92);
}

.co-card__no {
  margin: 0;
  font-family: var(--yb-font-mono);
  font-size: 13px;
  letter-spacing: 0.16em;
  color: var(--yb-orange);
}

.co-card__title {
  margin: 8px 0 12px;
  font-size: clamp(19px, 2.1vw, 24px);
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--co-ink);
}

.co-card__text {
  margin: 0;
  font-size: 15px;
  line-height: 1.8;
  color: var(--co-muted);
}

.co-card__materials {
  margin-top: 16px;
  padding-top: 16px;
  border-top: 2px dashed var(--co-line);
  max-height: none;
  opacity: 1;
  overflow: hidden;
}

.co-card__materials-title {
  margin: 0;
  font-family: var(--yb-font-mono);
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--co-muted);
}

.co-card__materials-list {
  margin: 10px 0 0;
  padding-left: 18px;
  font-size: 14px;
  line-height: 1.9;
  color: var(--co-ink);
}

/* ---------- 沟通流程 ---------- */
.co-flow__track {
  margin: clamp(30px, 4vw, 48px) 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 30px;
}

.co-flow__step {
  position: relative;
  padding-left: 76px;
  min-height: 60px;
}

.co-flow__step:not(:last-child)::after {
  content: "";
  position: absolute;
  left: 27px;
  top: 62px;
  bottom: -30px;
  width: 2px;
  background: var(--co-line);
}

.co-flow__node {
  position: absolute;
  left: 0;
  top: 0;
  width: 56px;
  height: 56px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  border: 3px solid var(--co-ink);
  background: var(--co-paper);
  font-family: var(--yb-font-mono);
  font-size: 15px;
  font-weight: 700;
  color: var(--co-ink);
  transition: background-color 0.22s var(--yb-ease),
    color 0.22s var(--yb-ease), transform 0.22s var(--yb-ease);
}

.co-flow__step:hover .co-flow__node,
.co-flow__step:focus-within .co-flow__node {
  background: var(--yb-cyan);
  color: var(--yb-navy);
  transform: scale(1.08);
}

.co-flow__title {
  margin: 4px 0 8px;
  font-size: clamp(17px, 1.8vw, 20px);
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--co-ink);
}

.co-flow__text {
  margin: 0;
  font-size: 15px;
  line-height: 1.8;
  color: var(--co-muted);
}

.co-flow__time {
  display: inline-block;
  margin-top: 12px;
  padding: 5px 11px;
  background: var(--yb-yellow);
  color: var(--yb-navy);
  font-family: var(--yb-font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  transition: transform 0.22s var(--yb-ease), background-color 0.22s var(--yb-ease);
}

.co-flow__step:hover .co-flow__time,
.co-flow__step:focus-within .co-flow__time {
  transform: translateY(-3px) scale(1.04);
  background: var(--yb-cyan);
}

.co-flow__note {
  margin: clamp(30px, 4vw, 44px) 0 0;
  padding-top: 18px;
  border-top: 2px solid var(--co-line);
  font-size: 14px;
  line-height: 1.8;
  color: var(--co-muted);
}

/* ---------- 联系方式（深色反转） ---------- */
.co-contact {
  position: relative;
  padding-top: clamp(88px, 11vw, 132px);
  padding-bottom: clamp(72px, 9vw, 110px);
}

.co-contact::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 58px;
  background: var(--yb-paper);
  clip-path: polygon(0 0, 100% 0, 68% 100%);
  pointer-events: none;
}

.co-contact__grid {
  align-items: start;
  row-gap: 44px;
}

.co-contact__lede {
  margin: 20px 0 0;
  max-width: 60ch;
  font-size: 16px;
  line-height: 1.85;
  color: var(--yb-muted);
}

.co-channels {
  margin: clamp(26px, 3.5vw, 40px) 0 0;
  padding: 0;
  list-style: none;
}

.co-channel {
  padding: 20px 0;
  border-top: 1px solid rgba(244, 246, 248, 0.18);
}

.co-channel:last-child {
  border-bottom: 1px solid rgba(244, 246, 248, 0.18);
}

.co-channel__label {
  display: block;
  font-family: var(--yb-font-mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  color: var(--yb-cyan);
}

.co-channel__value {
  display: block;
  margin-top: 9px;
  font-family: var(--yb-font-mono);
  font-size: clamp(15px, 1.9vw, 21px);
  font-weight: 600;
  color: var(--yb-paper);
  text-decoration: none;
  word-break: break-all;
  transition: color 0.2s var(--yb-ease), transform 0.2s var(--yb-ease);
}

.co-channel__value--plain {
  font-size: clamp(14px, 1.6vw, 17px);
  line-height: 1.7;
  color: var(--yb-paper);
}

a.co-channel__value:hover,
a.co-channel__value:focus-visible {
  color: var(--yb-cyan);
  transform: translateX(4px);
  outline: none;
}

.co-channel__note {
  display: block;
  margin-top: 8px;
  font-size: 13px;
  line-height: 1.7;
  color: rgba(244, 246, 248, 0.6);
}

.co-contact__figure {
  margin: 0;
}

/* ---------- 合作速答 ---------- */
.co-faq__list {
  margin-top: clamp(28px, 3.5vw, 44px);
}

.co-faq__item {
  border-top: 2px solid var(--co-line);
}

.co-faq__item:last-child {
  border-bottom: 2px solid var(--co-line);
}

.co-faq__q {
  display: flex;
  align-items: baseline;
  gap: 16px;
  padding: 20px 0;
  cursor: pointer;
  list-style: none;
  font-size: clamp(16px, 1.9vw, 19px);
  font-weight: 700;
  color: var(--co-ink);
  transition: color 0.2s var(--yb-ease);
}

.co-faq__q::-webkit-details-marker {
  display: none;
}

.co-faq__q:hover,
.co-faq__q:focus-visible {
  color: var(--yb-orange);
  outline: none;
}

.co-faq__no {
  flex: none;
  font-family: var(--yb-font-mono);
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--yb-orange);
}

.co-faq__text {
  flex: 1 1 auto;
}

.co-faq__mark {
  position: relative;
  flex: none;
  align-self: center;
  width: 18px;
  height: 18px;
}

.co-faq__mark::before,
.co-faq__mark::after {
  content: "";
  position: absolute;
  background: var(--co-ink);
  transition: transform 0.22s var(--yb-ease), background-color 0.22s var(--yb-ease);
}

.co-faq__mark::before {
  left: 0;
  top: 8px;
  width: 18px;
  height: 2px;
}

.co-faq__mark::after {
  left: 8px;
  top: 0;
  width: 2px;
  height: 18px;
}

.co-faq__item[open] .co-faq__mark::after {
  transform: scaleY(0);
}

.co-faq__item[open] .co-faq__mark::before {
  background: var(--yb-orange);
}

.co-faq__a {
  margin: 0;
  padding: 0 0 22px 40px;
  max-width: 68ch;
  font-size: 15px;
  line-height: 1.85;
  color: var(--co-muted);
}

.co-faq__more {
  margin: clamp(26px, 3.5vw, 38px) 0 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--co-muted);
}

.co-faq__more a {
  color: var(--co-ink);
  text-decoration: underline;
  text-decoration-color: var(--yb-cyan);
  text-decoration-thickness: 2px;
  text-underline-offset: 4px;
  transition: color 0.2s var(--yb-ease);
}

.co-faq__more a:hover,
.co-faq__more a:focus-visible {
  color: var(--yb-orange);
}

/* ---------- 响应式 ---------- */
@media (min-width: 900px) {
  .co-rail {
    position: sticky;
    top: calc(var(--yb-header-h) + 28px);
  }

  .co-card:nth-child(2) {
    margin-left: 22px;
  }

  .co-card:nth-child(3) {
    margin-left: 44px;
  }

  .co-card__materials {
    max-height: 0;
    opacity: 0;
    margin-top: 0;
    padding-top: 0;
    border-top-color: transparent;
    transition: max-height 0.28s var(--yb-ease), opacity 0.22s var(--yb-ease),
      margin-top 0.28s var(--yb-ease), padding-top 0.28s var(--yb-ease),
      border-top-color 0.28s var(--yb-ease);
  }

  .co-card:hover .co-card__materials,
  .co-card:focus-within .co-card__materials {
    max-height: 280px;
    opacity: 1;
    margin-top: 16px;
    padding-top: 16px;
    border-top-color: var(--co-line);
  }

  .co-flow__track {
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 26px;
  }

  .co-flow__step {
    padding-left: 0;
    padding-top: 78px;
    min-height: 0;
  }

  .co-flow__step:not(:last-child)::after {
    left: 62px;
    right: -26px;
    top: 27px;
    bottom: auto;
    width: auto;
    height: 2px;
  }

  .co-contact__figure {
    margin-top: 12px;
  }
}

@media (min-width: 1120px) {
  .co-hero__aside {
    padding-left: 28px;
  }
}

@media (max-width: 899px) {
  .co-contact::before {
    height: 36px;
    clip-path: polygon(0 0, 100% 0, 55% 100%);
  }

  .co-faq__a {
    padding-left: 0;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-contact .co-card,
  .page-contact .co-rail__item,
  .page-contact .co-flow__node,
  .page-contact .co-flow__time,
  .page-contact .co-channel__value,
  .page-contact .co-card__materials {
    transition-duration: 1ms;
  }

  .page-contact .co-card:hover,
  .page-contact .co-card:focus-within,
  .page-contact .co-rail__item:hover,
  .page-contact .co-rail__item:focus-visible,
  .page-contact .co-flow__step:hover .co-flow__node,
  .page-contact .co-flow__step:focus-within .co-flow__node {
    transform: none;
  }
}
</main>