/* ============================================================
   小步拓扑 StepTopo — styles.css
   风格基调：Rolex 式留白 × 未来感锐利影像
   ============================================================ */

:root {
  --black: #0a0a0a;
  --ink: #141414;
  --grey-dark: #8a8a8a;
  --grey: #6d6d6d;
  --line: #e4e1da;
  --paper: #faf9f7;
  --white: #ffffff;
  --gold: #c9a35c;
  --gold-deep: #a9863f;
  --font-sans: "PingFang SC", "HarmonyOS Sans SC", "Source Han Sans SC", "Microsoft YaHei", -apple-system, "Segoe UI", Helvetica, Arial, sans-serif;
  --ease: cubic-bezier(.22, .61, .36, 1);
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-sans);
  color: var(--ink);
  background: var(--white);
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

img { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
::selection { background: var(--gold); color: #fff; }

/* ---------- 布局基础 ---------- */
.container { width: min(1200px, 92%); margin: 0 auto; }
.container-narrow { width: min(760px, 92%); }

.section { padding: 168px 0; }
.section-light { background: var(--white); }
.section-dark { background: var(--black); color: var(--white); }

.eyebrow {
  font-size: 13px;
  letter-spacing: .42em;
  color: var(--gold-deep);
  margin-bottom: 28px;
  font-weight: 500;
}
.section-dark .eyebrow { color: var(--gold); }

h2 {
  font-size: clamp(34px, 4.6vw, 58px);
  font-weight: 300;
  line-height: 1.28;
  letter-spacing: .04em;
}

.section-sub {
  margin-top: 30px;
  font-size: 17px;
  color: var(--grey);
  max-width: 620px;
  font-weight: 300;
}
.section-dark .section-sub { color: #9a9a9a; }

.m { display: none; }

/* ---------- 按钮 ---------- */
.btn {
  display: inline-block;
  padding: 15px 42px;
  font-size: 14px;
  letter-spacing: .3em;
  text-indent: .3em;
  border: 1px solid transparent;
  transition: all .45s var(--ease);
  cursor: pointer;
  background: none;
  font-family: inherit;
}
.btn-gold {
  background: var(--gold);
  color: #fff;
  border-color: var(--gold);
}
.btn-gold:hover { background: var(--gold-deep); border-color: var(--gold-deep); }
.btn-ghost {
  color: #fff;
  border-color: rgba(255,255,255,.55);
}
.btn-ghost:hover { background: #fff; color: var(--black); border-color: #fff; }
.btn-small { padding: 9px 22px; font-size: 12px; }

/* ---------- 导航 ---------- */
.nav {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 100;
  transition: background .5s var(--ease), box-shadow .5s var(--ease);
}
.nav.scrolled {
  background: rgba(250, 249, 247, .92);
  backdrop-filter: blur(14px);
  box-shadow: 0 1px 0 var(--line);
}
.nav-inner {
  width: min(1280px, 94%);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 76px;
}
.brand { display: flex; align-items: center; gap: 12px; color: #fff; transition: color .5s var(--ease); }
.nav.scrolled .brand { color: var(--ink); }
.brand-mark { width: 26px; height: 26px; }
.brand-text {
  font-size: 17px;
  letter-spacing: .18em;
  font-weight: 500;
  display: flex;
  flex-direction: column;
  line-height: 1.1;
}
.brand-text em {
  font-style: normal;
  font-size: 9px;
  letter-spacing: .52em;
  color: var(--gold);
  font-weight: 400;
}
.nav-links { display: flex; align-items: center; gap: 40px; }
.nav-links > a {
  font-size: 13.5px;
  letter-spacing: .2em;
  color: rgba(255,255,255,.85);
  position: relative;
  padding: 4px 0;
  transition: color .4s var(--ease);
}
.nav.scrolled .nav-links > a { color: var(--ink); }
.nav-links > a:not(.btn)::after {
  content: "";
  position: absolute;
  left: 0; bottom: -4px;
  width: 0; height: 1px;
  background: var(--gold);
  transition: width .45s var(--ease);
}
.nav-links > a:not(.btn):hover::after { width: 100%; }
.nav-links > a.btn { color: #fff; }
.nav-toggle { display: none; }

/* ---------- Hero ---------- */
.hero {
  position: relative;
  min-height: 100vh;
  min-height: 100svh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  color: #fff;
  overflow: hidden;
  background: var(--black);
}
.hero-bg {
  position: absolute;
  inset: 0;
  width: 100%; height: 100%;
  object-fit: cover;
  object-position: center 40%;
  transform: scale(1.06);
  animation: heroZoom 3.2s var(--ease) forwards;
}
@keyframes heroZoom { to { transform: scale(1); } }
.hero-veil {
  position: absolute; inset: 0;
  background: linear-gradient(180deg, rgba(10,10,10,.55) 0%, rgba(10,10,10,.25) 45%, rgba(10,10,10,.72) 100%);
}
.hero-content { position: relative; z-index: 2; padding: 120px 24px 0; }
.hero-eyebrow {
  font-size: 13px;
  letter-spacing: .6em;
  text-indent: .6em;
  color: var(--gold);
  margin-bottom: 34px;
}
.hero h1 {
  font-size: clamp(40px, 7.2vw, 92px);
  font-weight: 200;
  letter-spacing: .1em;
  line-height: 1.32;
}
.hero-sub {
  margin-top: 40px;
  font-size: clamp(14px, 1.5vw, 17px);
  color: rgba(255,255,255,.82);
  font-weight: 300;
  letter-spacing: .06em;
  line-height: 2.1;
}
.hero-actions { margin-top: 56px; display: flex; gap: 18px; justify-content: center; flex-wrap: wrap; }

.hero-scroll {
  position: absolute;
  bottom: 34px; left: 50%;
  transform: translateX(-50%);
  width: 1px; height: 56px;
  background: rgba(255,255,255,.25);
  overflow: hidden;
}
.hero-scroll span {
  position: absolute;
  top: -50%;
  width: 100%; height: 50%;
  background: var(--gold);
  animation: scrollLine 2.2s var(--ease) infinite;
}
@keyframes scrollLine { to { top: 110%; } }

/* ---------- 品牌理念 ---------- */
.idea-text { margin-top: 64px; max-width: 780px; }
.idea-text .lead {
  font-size: clamp(18px, 2vw, 23px);
  font-weight: 300;
  line-height: 2;
  color: var(--ink);
  margin-bottom: 34px;
}
.idea-text p:last-child { color: var(--grey); font-size: 16px; font-weight: 300; }

.grid-3 {
  margin-top: 110px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}
.principle {
  background: var(--white);
  padding: 62px 48px;
  transition: background .5s var(--ease);
}
.principle:hover { background: var(--paper); }
.principle-num {
  display: block;
  font-size: 15px;
  color: var(--gold-deep);
  letter-spacing: .3em;
  margin-bottom: 30px;
}
.principle h3 { font-size: 19px; font-weight: 500; letter-spacing: .08em; margin-bottom: 18px; }
.principle p { font-size: 15px; color: var(--grey); font-weight: 300; }

/* ---------- 十大方向 ---------- */
.dir-grid {
  margin-top: 100px;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 48px 56px;
}
.dir-card { display: block; color: inherit; }
.dir-media {
  overflow: hidden;
  aspect-ratio: 4 / 5;
  max-height: 520px;
  background: #111;
}
.dir-media img {
  width: 100%; height: 100%;
  object-fit: cover;
  transform: scale(1.001);
  transition: transform 1.4s var(--ease), opacity .6s var(--ease);
  opacity: .96;
}
.dir-card:hover .dir-media img { transform: scale(1.055); opacity: 1; }
.dir-body { padding: 30px 4px 0; }
.dir-num {
  font-size: 12px;
  letter-spacing: .35em;
  color: var(--gold);
}
.dir-body h3 {
  margin-top: 12px;
  font-size: 24px;
  font-weight: 400;
  letter-spacing: .1em;
  display: flex;
  align-items: baseline;
  gap: 14px;
}
.dir-body h3 em {
  font-style: normal;
  font-size: 12px;
  letter-spacing: .32em;
  text-transform: uppercase;
  color: var(--grey-dark);
}
.dir-tagline {
  margin-top: 14px;
  font-size: 15px;
  color: var(--gold);
  letter-spacing: .12em;
}
.dir-desc {
  margin-top: 10px;
  font-size: 14.5px;
  color: #9a9a9a;
  font-weight: 300;
  max-width: 480px;
}

/* ---------- 方法论 ---------- */
.steps {
  margin-top: 96px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: var(--line);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.step {
  background: var(--white);
  padding: 56px 38px;
}
.step-num {
  font-size: 44px;
  font-weight: 200;
  color: var(--gold-deep);
  letter-spacing: .04em;
  display: block;
  margin-bottom: 34px;
}
.step h3 { font-size: 18px; font-weight: 500; letter-spacing: .06em; margin-bottom: 16px; }
.step p { font-size: 14.5px; color: var(--grey); font-weight: 300; }

/* ---------- 宣言横幅 ---------- */
.quote {
  background: var(--black);
  color: #fff;
  text-align: center;
  padding: 190px 0;
}
.quote p {
  font-size: clamp(24px, 3.4vw, 42px);
  font-weight: 200;
  letter-spacing: .12em;
  line-height: 1.9;
}
.quote span {
  display: block;
  margin-top: 44px;
  font-size: 13px;
  letter-spacing: .4em;
  text-indent: .4em;
  color: var(--gold);
}

/* ---------- 加入 ---------- */
.join { text-align: center; background: var(--paper); }
.join .section-sub { margin-left: auto; margin-right: auto; }
.join-form {
  margin: 58px auto 0;
  display: flex;
  max-width: 560px;
  border: 1px solid var(--ink);
  background: var(--white);
}
.join-form input {
  flex: 1;
  border: none;
  outline: none;
  padding: 0 26px;
  font-size: 15px;
  font-family: inherit;
  background: transparent;
  min-width: 0;
}
.join-form .btn { border: none; white-space: nowrap; }
.join-tip { margin-top: 20px; font-size: 14px; color: var(--gold-deep); min-height: 22px; letter-spacing: .06em; }
.join-alt { margin-top: 46px; font-size: 14px; color: var(--grey); }
.join-alt a { color: var(--ink); border-bottom: 1px solid var(--gold); padding-bottom: 2px; transition: color .3s; }
.join-alt a:hover { color: var(--gold-deep); }

/* ---------- 页脚 ---------- */
.footer { background: var(--black); color: #b5b5b5; padding: 96px 0 46px; }
.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
}
.footer-brand .brand { color: #fff; margin-bottom: 26px; display: inline-flex; }
.footer-brand p { font-size: 14px; font-weight: 300; line-height: 2; color: #8f8f8f; }
.footer-col h4 {
  color: #fff;
  font-size: 13px;
  letter-spacing: .3em;
  font-weight: 500;
  margin-bottom: 24px;
}
.footer-col a {
  display: block;
  font-size: 14px;
  color: #8f8f8f;
  margin-bottom: 14px;
  transition: color .3s;
}
.footer-col a:hover { color: var(--gold); }
.footer-bottom {
  margin-top: 80px;
  padding-top: 28px;
  border-top: 1px solid #222;
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
  font-size: 12.5px;
  color: #666;
}
.footer-bottom a { color: #666; transition: color .3s; }
.footer-bottom a:hover { color: var(--gold); }

/* ---------- 揭示动画 ---------- */
.reveal {
  opacity: 0;
  transform: translateY(34px);
  transition: opacity 1s var(--ease), transform 1s var(--ease);
  transition-delay: var(--d, 0s);
}
.reveal.in { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) {
  .reveal { opacity: 1; transform: none; transition: none; }
  .hero-bg { animation: none; transform: none; }
  html { scroll-behavior: auto; }
}

/* ---------- 关于页 ---------- */
.page-hero {
  padding: 200px 0 120px;
  background: var(--black);
  color: #fff;
  text-align: center;
}
.page-hero .eyebrow { color: var(--gold); }
.page-hero p.sub {
  margin-top: 30px;
  color: #9a9a9a;
  font-weight: 300;
  letter-spacing: .08em;
  font-size: 16px;
}
.about-block { max-width: 780px; margin: 0 auto; }
.about-block h3 {
  font-size: 26px;
  font-weight: 400;
  letter-spacing: .12em;
  margin-bottom: 26px;
}
.about-block p { margin-bottom: 22px; color: var(--grey); font-weight: 300; font-size: 16px; }
.about-block p.lead { color: var(--ink); font-size: 19px; line-height: 2; }
.about-divider { width: 44px; height: 1px; background: var(--gold); margin: 0 auto; }
.about-section { padding: 120px 0; }
.about-section:nth-of-type(even) { background: var(--paper); }
.values-grid {
  margin-top: 70px;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}
.value-card { background: var(--white); padding: 50px 44px; }
.value-card h4 { font-size: 17px; letter-spacing: .1em; margin-bottom: 14px; font-weight: 500; }
.value-card p { font-size: 14.5px; color: var(--grey); font-weight: 300; margin: 0; }

/* ---------- 404 ---------- */
.err {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  background: var(--black);
  color: #fff;
  padding: 40px 24px;
}
.err .code {
  font-size: clamp(90px, 18vw, 200px);
  font-weight: 200;
  letter-spacing: .1em;
  line-height: 1;
  color: var(--gold);
}
.err h1 { font-size: clamp(22px, 3vw, 32px); font-weight: 300; letter-spacing: .14em; margin-top: 36px; }
.err p { color: #8a8a8a; margin-top: 18px; font-weight: 300; }
.err .btn { margin-top: 52px; }

/* ---------- 响应式 ---------- */
@media (max-width: 1024px) {
  .section { padding: 120px 0; }
  .dir-grid { gap: 40px; }
  .steps { grid-template-columns: repeat(2, 1fr); }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 768px) {
  .m { display: inline; }
  .section { padding: 96px 0; }
  .grid-3 { grid-template-columns: 1fr; }
  .dir-grid { grid-template-columns: 1fr; gap: 56px; }
  .steps { grid-template-columns: 1fr; }
  .values-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; gap: 40px; }
  .quote { padding: 130px 0; }
  .join-form { flex-direction: column; border: none; background: none; gap: 14px; }
  .join-form input { border: 1px solid var(--ink); padding: 15px 22px; background: #fff; }
  .join-form .btn { width: 100%; }

  .nav-toggle {
    display: flex;
    flex-direction: column;
    gap: 7px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 10px;
    z-index: 110;
  }
  .nav-toggle span {
    width: 24px; height: 1.5px;
    background: #fff;
    transition: all .4s var(--ease);
  }
  .nav.scrolled .nav-toggle span,
  .nav.open .nav-toggle span { background: var(--ink); }
  .nav.open .nav-toggle span:nth-child(1) { transform: translateY(4.2px) rotate(45deg); }
  .nav.open .nav-toggle span:nth-child(2) { transform: translateY(-4.2px) rotate(-45deg); }

  .nav-links {
    position: fixed;
    inset: 0;
    background: rgba(250,249,247,.98);
    flex-direction: column;
    justify-content: center;
    gap: 34px;
    opacity: 0;
    visibility: hidden;
    transition: opacity .5s var(--ease), visibility .5s;
  }
  .nav.open .nav-links { opacity: 1; visibility: visible; }
  .nav-links > a { font-size: 18px; color: var(--ink) !important; }
  .nav-toggle { position: relative; z-index: 120; }
  .nav.open .nav-toggle span { background: var(--ink); }
}