/* ==========================================================================
   基础层 · 重置、纸底、排版、章节骨架、焦点、动效降级
   ========================================================================== */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 84px;
}

body {
  margin: 0;
  background-color: var(--paper);
  background-image:
    radial-gradient(70rem 44rem at 88% -8%, rgba(192, 160, 98, 0.1), transparent 60%),
    radial-gradient(52rem 40rem at 4% 2%, rgba(255, 255, 255, 0.9), transparent 62%);
  color: var(--text);
  font-family: var(--font-body);
  font-size: var(--step-0);
  line-height: 1.85;
  letter-spacing: 0.01em;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* 极轻纸纹，20 米外看不出来，但能消除屏幕的白噪 */
.grain {
  position: fixed;
  inset: 0;
  z-index: 8;
  pointer-events: none;
  opacity: 0.028;
  mix-blend-mode: multiply;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='200' height='200'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='3'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

img {
  display: block;
  max-width: 100%;
  height: auto;
}

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

p {
  margin: 0;
}

h1,
h2,
h3,
h4 {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 900;
  line-height: 1.15;
  letter-spacing: -0.01em;
}

ul,
ol,
dl,
dd,
dt,
figure,
blockquote {
  margin: 0;
  padding: 0;
}

li {
  list-style: none;
}

strong {
  font-weight: 700;
}

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

/* 版心 */
.wrap {
  width: 100%;
  min-width: 0;
  max-width: 76rem;
  margin-inline: auto;
  padding-inline: var(--space-4);
}

@media (min-width: 900px) {
  .wrap {
    padding-inline: var(--space-6);
  }
}

/* 章节 */
.section {
  position: relative;
  padding-block: var(--space-7);
}

@media (min-width: 900px) {
  .section {
    padding-block: var(--space-8);
  }
}

.section--tight {
  padding-block: var(--space-6);
}

/* 整幅浅色带，用来在连续的白纸章节之间打断一下节奏 */
.section--band {
  background: var(--paper-3);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

/* 章节头：左侧编号标签，右侧大标题，故意非对称 */
.section-head {
  display: grid;
  gap: var(--space-3);
  margin-bottom: var(--space-5);
}

@media (min-width: 900px) {
  .section-head {
    grid-template-columns: minmax(140px, 0.34fr) 1fr;
    gap: var(--space-6);
    align-items: start;
    margin-bottom: var(--space-6);
  }
}

.kicker {
  display: flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-display);
  font-size: var(--step--2);
  font-weight: 700;
  letter-spacing: 0.18em;
  color: var(--gold-deep);
  padding-top: 0.5em;
}

.kicker::before {
  content: "";
  width: 22px;
  height: 1px;
  background: var(--gold);
  flex: none;
}

.sec-title {
  font-size: var(--step-3);
  line-height: 1.18;
  letter-spacing: -0.02em;
  max-width: 18em;
}

.sec-title em {
  font-style: normal;
  color: var(--gold);
}

.lede {
  max-width: var(--measure);
  color: var(--muted);
  font-size: var(--step-0);
}

/* 不让固定词组被拆到两行，例如"一对一" */
.nowrap {
  white-space: nowrap;
}

/* 入场 */
.reveal {
  opacity: 0;
  transform: translateY(22px);
  transition:
    opacity var(--dur-slow) var(--ease-out),
    transform var(--dur-slow) var(--ease-out);
}

.reveal.in {
  opacity: 1;
  transform: none;
}

@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;
  }

  .reveal {
    opacity: 1;
    transform: none;
  }
}