:root {
  --paper: #faf8f4;
  --ink: #1a1714;
  --ink-2: #4c463d;
  --ink-3: #8a8279;
  --rule: #ded7ca;
  --deep: #22332c;
  --accent: #2f5d4b;
  --serif: "Source Han Serif SC", "Songti SC", "SimSun", "STSong", serif;
  --sans: "Source Han Sans SC", "Microsoft YaHei UI", "PingFang SC", system-ui, sans-serif;
  --mono: ui-monospace, "Cascadia Mono", Consolas, monospace;
}

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

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
  text-wrap: pretty;
}

a {
  color: inherit;
}

:focus-visible {
  outline: 2px solid var(--deep);
  outline-offset: 3px;
}

.shell {
  width: min(66rem, 100% - 3.5rem);
  margin-inline: auto;
}

/* 报头 */
.masthead {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 2rem;
  padding: 1.3rem 0 1rem;
  border-bottom: 2px solid var(--ink);
}

.masthead .logo {
  font-family: var(--serif);
  font-size: 1.45rem;
  letter-spacing: 0.3em;
  text-decoration: none;
}

.masthead nav {
  display: flex;
  gap: 1.7rem;
  font-size: 0.86rem;
  color: var(--ink-2);
}

.masthead nav a {
  text-decoration: none;
  border-bottom: 1px solid transparent;
  padding-bottom: 2px;
  transition: border-color 0.16s ease;
}

.masthead nav a:hover {
  border-bottom-color: var(--ink);
}

/* 首屏 */
.hero {
  padding: clamp(3rem, 8vw, 6rem) 0 clamp(2.4rem, 5vw, 3.6rem);
  border-bottom: 1px solid var(--rule);
}

.hero h1 {
  margin: 0 0 1.8rem;
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(2.6rem, 8.4vw, 6.2rem);
  line-height: 1.14;
  letter-spacing: 0.04em;
}

.hero h1 .ask {
  color: var(--ink-3);
}

.hero h1 .answer {
  color: var(--accent);
}

.hero-lede {
  display: grid;
  grid-template-columns: 12rem minmax(0, 1fr);
  gap: clamp(1.2rem, 3vw, 3rem);
  align-items: start;
  margin-top: 2.6rem;
}

.hero-lede .label {
  font-family: var(--serif);
  font-size: 0.92rem;
  color: var(--ink-3);
  border-top: 1px solid var(--ink);
  padding-top: 0.7rem;
  line-height: 1.9;
}

.hero-lede .body p {
  margin: 0 0 1rem;
  max-width: 36rem;
  font-size: 1.02rem;
  color: var(--ink-2);
}

.hero-lede .body p:last-child {
  margin-bottom: 0;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.9rem;
  margin-top: 2rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.72rem 1.5rem;
  border-radius: 4px;
  border: 1px solid transparent;
  font-size: 0.95rem;
  font-weight: 600;
  text-decoration: none;
  transition: background 0.16s ease, transform 0.12s ease;
}

.btn-solid {
  background: #2c2822;
  color: var(--paper);
}

.btn-solid:hover {
  background: #3b362e;
}

.btn-solid:active {
  transform: scale(0.98);
}

.btn-line {
  border-color: var(--rule);
  color: var(--ink);
}

.btn-line:hover {
  border-color: var(--ink);
}

/* 章节 */
.chapter {
  padding: clamp(2.6rem, 5vw, 4rem) 0;
  border-bottom: 1px solid var(--rule);
}

.chapter-head {
  display: grid;
  grid-template-columns: 12rem minmax(0, 1fr);
  gap: clamp(1.2rem, 3vw, 3rem);
  align-items: baseline;
  margin-bottom: 2rem;
}

.chapter-head h2 {
  margin: 0;
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(1.6rem, 3.4vw, 2.4rem);
  letter-spacing: 0.04em;
}

.chapter-head .index {
  font-family: var(--serif);
  font-size: 0.9rem;
  color: var(--ink-3);
  border-top: 1px solid var(--ink);
  padding-top: 0.7rem;
}

.chapter-note {
  margin: 0 0 2rem;
  max-width: 38rem;
  color: var(--ink-2);
  font-size: 0.98rem;
}

/* 四层记忆 */
.layers {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 12rem), 1fr));
  gap: 0;
  border-top: 1px solid var(--ink);
}

.layer {
  padding: 1.3rem 1.4rem 1.5rem 0;
  border-right: 1px solid var(--rule);
}

.layer:last-child {
  border-right: none;
}

.layer h3 {
  margin: 0 0 0.35rem;
  font-family: var(--serif);
  font-weight: 400;
  font-size: 1.12rem;
  letter-spacing: 0.04em;
}

.layer p {
  margin: 0;
  font-size: 0.88rem;
  color: var(--ink-2);
  line-height: 1.75;
}

/* 机制条目 */
.mechanism {
  display: grid;
  grid-template-columns: 12rem minmax(0, 1fr);
  gap: 0.4rem clamp(1.2rem, 3vw, 3rem);
  padding: 1.5rem 0;
  border-top: 1px solid var(--rule);
}

.mechanism h3 {
  margin: 0;
  font-family: var(--serif);
  font-weight: 400;
  font-size: 1.16rem;
  letter-spacing: 0.05em;
}

.mechanism .detail p {
  margin: 0 0 0.55rem;
  max-width: 36rem;
  font-size: 0.94rem;
  color: var(--ink-2);
}

.mechanism .detail p:last-child {
  margin-bottom: 0;
}

/* 引文：整页唯一的深色块 */
.creed {
  background: var(--deep);
  color: #f2efe7;
  padding: clamp(3rem, 7vw, 5rem) 0;
}

.creed p {
  width: min(44rem, 100% - 3.5rem);
  margin: 0 auto;
  font-family: var(--serif);
  font-size: clamp(1.3rem, 3vw, 1.95rem);
  line-height: 1.75;
  letter-spacing: 0.03em;
}

.creed p em {
  font-style: normal;
  color: #9fc4ad;
}

/* UI 预览 */
.preview-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 20rem), 1fr));
  gap: 1.4rem;
}

.preview-card {
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.preview-card a {
  display: block;
  border: 1px solid var(--rule);
  background: #fff;
  overflow: hidden;
  transition: border-color 0.18s ease, transform 0.18s ease;
}

.preview-card a:hover {
  border-color: var(--ink);
  transform: translateY(-2px);
}

.preview-card img {
  display: block;
  width: 100%;
  height: auto;
}

.preview-card figcaption {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  font-size: 0.8rem;
  color: var(--ink-3);
}

.preview-card figcaption strong {
  font-weight: 600;
  color: var(--ink-2);
}

/* 群与下载 */
.closing {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 15rem;
  gap: 2rem;
  align-items: end;
  padding: clamp(2.4rem, 5vw, 3.6rem) 0;
}

.closing h2 {
  margin: 0 0 0.7rem;
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(1.6rem, 3.2vw, 2.2rem);
  letter-spacing: 0.04em;
}

.closing p {
  margin: 0 0 0.6rem;
  max-width: 34rem;
  font-size: 0.94rem;
  color: var(--ink-2);
}

.qq {
  font-family: var(--mono);
  font-size: 1.05rem;
  letter-spacing: 0.06em;
  color: var(--ink);
}

footer {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.5rem 2rem;
  padding: 1.4rem 0 2.8rem;
  border-top: 1px solid var(--rule);
  font-size: 0.78rem;
  color: var(--ink-3);
}

footer a {
  text-decoration: none;
  border-bottom: 1px solid var(--rule);
}

/* 预览页 */
.gallery {
  display: grid;
  gap: clamp(1.6rem, 3vw, 2.6rem);
  padding: clamp(2rem, 4vw, 3rem) 0;
}

.screen {
  margin: 0;
}

.screen img {
  display: block;
  width: 100%;
  height: auto;
  border: 1px solid var(--rule);
  background: #fff;
}

.screen figcaption {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.4rem 1.5rem;
  margin-top: 0.65rem;
  font-size: 0.82rem;
  color: var(--ink-3);
}

.screen figcaption b {
  font-family: var(--serif);
  font-weight: 400;
  font-size: 0.98rem;
  color: var(--ink);
}

.screen figcaption span {
  letter-spacing: 0.02em;
}

@media (max-width: 820px) {
  .shell {
    width: min(66rem, 100% - 2.2rem);
  }

  .hero-lede,
  .chapter-head,
  .mechanism,
  .closing {
    grid-template-columns: minmax(0, 1fr);
  }

  .hero-lede .label {
    border-top: none;
    border-left: 2px solid var(--ink);
    padding: 0 0 0 0.8rem;
  }

  .chapter-head .index {
    border-top: none;
    border-left: 2px solid var(--ink);
    padding: 0 0 0 0.8rem;
  }

  .layer {
    border-right: none;
    border-bottom: 1px solid var(--rule);
    padding-right: 0;
  }

  .layer:last-child {
    border-bottom: none;
  }
}

@media (prefers-reduced-motion: reduce) {
  * {
    transition-duration: 0.01ms !important;
  }
}