@import url('https://fonts.googleapis.com/css2?family=Nunito+Sans:wght@300;400;500;600;700&family=Rubik:wght@300;400;500;600;700&display=swap');

/* ========================
   CSS 变量 & 基础重置
======================== */
:root {
  --c-black: #000000;
  --c-white: #ffffff;
  --c-accent: #000000;
  --c-gray-100: #f5f5f5;
  --c-gray-200: #e0e0e0;
  --c-gray-400: #999999;
  --c-gray-700: #333333;

  --font-main: 'Rubik', 'Nunito Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif;

  --base: 8px;
  --sp1: 8px;
  --sp2: 16px;
  --sp3: 24px;
  --sp4: 32px;
  --sp5: 40px;
  --sp6: 48px;
  --sp8: 64px;
  --sp10: 80px;
  --sp12: 96px;

  --nav-h: 100px;
  --radius: 4px;
  --max-w: 1200px;
  --transition: 0.22s ease;
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
  background: var(--c-white);
  color: var(--c-black);
}

body {
  font-family: var(--font-main);
  font-weight: 400;
  line-height: 1.6;
  min-height: 100vh;
  background: var(--c-white);
  color: var(--c-black);
  overflow-x: hidden;
}

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

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

/* ========================
   滚动偏移（固定导航）
======================== */
article {
  scroll-margin-top: var(--nav-h);
}

/* ========================
   Header
======================== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--c-black);
  color: var(--c-white);
  border-bottom: 2px solid var(--c-white);
}

.header-brand-row {
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: center;
  max-width: var(--max-w);
  margin: 0 auto;
  padding: var(--sp2) var(--sp4);
  gap: var(--sp2);
}

.brand-home-link {
  display: inline-flex;
  align-items: center;
  gap: var(--sp2);
}

.site-logo {
  height: 40px;
  width: auto;
}

.logo-text {
  font-family: var(--font-main);
  font-size: 1.35rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--c-white);
  line-height: 1.2;
}

.btn-cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 40px;
  padding: var(--sp1) var(--sp3);
  background: var(--c-white);
  color: var(--c-black);
  font-family: var(--font-main);
  font-size: 0.875rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  border: 2px solid var(--c-white);
  border-radius: var(--radius);
  cursor: pointer;
  transition: background var(--transition), color var(--transition);
  white-space: nowrap;
}
.btn-cta:hover,
.btn-cta:focus-visible {
  background: var(--c-black);
  color: var(--c-white);
  outline: 2px solid var(--c-white);
  outline-offset: 2px;
}

.header-nav-row {
  border-top: 1px solid rgba(255,255,255,0.15);
  background: var(--c-black);
}

.main-nav {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 var(--sp4);
}

.nav-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0;
  align-items: stretch;
}

.nav-links a {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  padding: var(--sp1) var(--sp3);
  font-size: 0.875rem;
  font-weight: 500;
  letter-spacing: 0.04em;
  color: rgba(255,255,255,0.8);
  border-right: 1px solid rgba(255,255,255,0.1);
  transition: color var(--transition), background var(--transition);
  white-space: nowrap;
}
.nav-links a:first-child {
  border-left: 1px solid rgba(255,255,255,0.1);
}
.nav-links a:hover,
.nav-links a:focus-visible {
  color: var(--c-white);
  background: rgba(255,255,255,0.08);
  outline: none;
}

/* ========================
   Hero
======================== */
.hero-section {
  position: relative;
  width: 100%;
  height: 100vh;
  min-height: 560px;
  display: flex;
  align-items: flex-end;
  overflow: hidden;
  background: var(--c-black);
}

.hero-media {
  position: absolute;
  inset: 0;
  z-index: 0;
}

.hero-media .hero-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center;
}

.hero-no-img {
  background: linear-gradient(135deg, #111 0%, #333 100%);
}

.hero-mask {
  position: absolute;
  inset: 0;
  background: linear-gradient(
    to top,
    rgba(0,0,0,0.88) 0%,
    rgba(0,0,0,0.45) 50%,
    rgba(0,0,0,0.18) 100%
  );
  z-index: 1;
}

.hero-content {
  position: relative;
  z-index: 2;
  max-width: var(--max-w);
  width: 100%;
  margin: 0 auto;
  padding: var(--sp12) var(--sp4) var(--sp10);
  text-align: left;
}

.hero-h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.15;
  color: var(--c-white);
  margin-bottom: var(--sp3);
  max-width: 720px;
}

.hero-desc {
  font-size: clamp(1rem, 2vw, 1.2rem);
  font-weight: 300;
  line-height: 1.7;
  color: rgba(255,255,255,0.8);
  margin-bottom: var(--sp5);
  max-width: 560px;
}

.btn-hero {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: var(--sp2) var(--sp5);
  background: var(--c-white);
  color: var(--c-black);
  font-family: var(--font-main);
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  border: 2px solid var(--c-white);
  border-radius: var(--radius);
  cursor: pointer;
  transition: background var(--transition), color var(--transition), transform var(--transition);
}
.btn-hero:hover,
.btn-hero:focus-visible {
  background: transparent;
  color: var(--c-white);
  transform: translateY(-2px);
  outline: 2px solid var(--c-white);
  outline-offset: 2px;
}

/* ========================
   Main Layout
======================== */
.site-main {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: var(--sp8) var(--sp4);
}

.main-article {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: var(--sp6);
  align-items: start;
}

/* ========================
   Aside
======================== */
.content-aside {
  position: sticky;
  top: calc(var(--nav-h) + var(--sp3));
}

.aside-inner {
  background: var(--c-black);
  color: var(--c-white);
  border-radius: var(--radius);
  padding: var(--sp4) var(--sp3);
}

.aside-title {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  margin-bottom: var(--sp2);
}

.aside-inner hr {
  border: none;
  border-top: 1px solid rgba(255,255,255,0.2);
  margin-bottom: var(--sp3);
}

.aside-inner nav {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.aside-link {
  display: block;
  padding: 10px var(--sp2);
  font-size: 0.8125rem;
  font-weight: 400;
  line-height: 1.4;
  color: rgba(255,255,255,0.75);
  border-radius: calc(var(--radius) / 2);
  transition: background var(--transition), color var(--transition);
  min-height: 40px;
  display: flex;
  align-items: center;
}
.aside-link:hover,
.aside-link:focus-visible {
  background: rgba(255,255,255,0.12);
  color: var(--c-white);
  outline: none;
}

/* ========================
   Content Body
======================== */
.content-body {
  min-width: 0;
}

/* content 内部 article 样式 */
.content-body article {
  padding: var(--sp8) 0;
  border-bottom: 1px solid var(--c-gray-200);
}
.content-body article:last-child {
  border-bottom: none;
}

.content-body h2 {
  font-size: clamp(1.4rem, 3vw, 2rem);
  font-weight: 700;
  letter-spacing: -0.01em;
  line-height: 1.2;
  margin-bottom: var(--sp2);
}

.content-body h2 + hr {
  border: none;
  border-top: 3px solid var(--c-black);
  margin-bottom: var(--sp4);
}

.content-body h3 {
  font-size: 1.2rem;
  font-weight: 600;
  margin-top: var(--sp4);
  margin-bottom: var(--sp2);
}

.content-body h3 + hr {
  border: none;
  border-top: 1px solid var(--c-black);
  margin-bottom: var(--sp3);
}

.content-body p {
  font-size: 1rem;
  line-height: 1.75;
  margin-bottom: var(--sp3);
  color: var(--c-gray-700);
}

.content-body ul,
.content-body ol {
  padding-left: var(--sp4);
  margin-bottom: var(--sp3);
}

.content-body li {
  font-size: 1rem;
  line-height: 1.7;
  margin-bottom: var(--sp1);
  color: var(--c-gray-700);
}

.content-body strong {
  font-weight: 700;
  color: var(--c-black);
}

.content-body a {
  color: var(--c-black);
  text-decoration: underline;
  text-underline-offset: 3px;
  transition: opacity var(--transition);
}
.content-body a:hover {
  opacity: 0.6;
}

.content-body blockquote {
  border-left: 4px solid var(--c-black);
  padding-left: var(--sp3);
  margin: var(--sp4) 0;
  font-style: italic;
  color: var(--c-gray-400);
}

/* ========================
   Footer
======================== */
.site-footer {
  background: var(--c-black);
  color: var(--c-white);
  padding: var(--sp10) var(--sp4) var(--sp6);
  text-align: center;
  overflow: hidden;
}

.footer-brand-big {
  font-size: clamp(2.5rem, 8vw, 6rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1;
  margin-bottom: var(--sp6);
  opacity: 0.08;
  user-select: none;
  pointer-events: none;
}

.footer-copy {
  font-size: 0.875rem;
  font-weight: 400;
  color: rgba(255,255,255,0.7);
  margin-bottom: var(--sp2);
  line-height: 1.6;
}

.footer-note {
  display: block;
  font-size: 0.75rem;
  color: rgba(255,255,255,0.4);
  line-height: 1.5;
  max-width: 600px;
  margin: 0 auto;
}

/* ========================
   Scroll Reveal Animation
======================== */
@media (prefers-reduced-motion: no-preference) {
  .reveal {
    opacity: 0;
    transform: translateY(24px);
    transition: opacity 0.5s ease, transform 0.5s ease;
  }
  .reveal.visible {
    opacity: 1;
    transform: none;
  }

  .aside-link {
    transition: background var(--transition), color var(--transition), transform var(--transition);
  }
  .aside-link:hover {
    transform: translateX(4px);
  }
}

@media (prefers-reduced-motion: reduce) {
  .reveal {
    opacity: 1;
    transform: none;
  }
}

/* ========================
   响应式
======================== */
@media (max-width: 900px) {
  .main-article {
    grid-template-columns: 1fr;
  }

  .content-aside {
    position: static;
    order: -1;
  }

  .aside-inner {
    padding: var(--sp3) var(--sp3);
  }

  .aside-inner nav {
    flex-direction: row;
    flex-wrap: wrap;
    gap: var(--sp1);
  }

  .aside-link {
    min-height: 40px;
    padding: var(--sp1) var(--sp2);
    font-size: 0.8rem;
  }

  .header-brand-row {
    padding: var(--sp2) var(--sp3);
  }

  .main-nav {
    padding: 0 var(--sp3);
  }
}

@media (max-width: 600px) {
  :root {
    --nav-h: 110px;
  }

  .header-brand-row {
    padding: var(--sp2);
    gap: var(--sp1);
  }

  .logo-text {
    font-size: 1.1rem;
  }

  .btn-cta {
    font-size: 0.8rem;
    padding: var(--sp1) var(--sp2);
    min-height: 40px;
  }

  .nav-links a {
    font-size: 0.78rem;
    padding: var(--sp1) var(--sp2);
    min-height: 44px;
  }

  .hero-content {
    padding: var(--sp10) var(--sp3) var(--sp8);
  }

  .site-main {
    padding: var(--sp5) var(--sp3);
  }

  .content-body article {
    padding: var(--sp5) 0;
  }

  .aside-inner nav {
    gap: 4px;
  }

  .footer-brand-big {
    font-size: clamp(2rem, 12vw, 4rem);
  }
}

/* ========================
   HR 全局
======================== */
hr {
  border: none;
  border-top: 1px solid var(--c-gray-200);
  margin: var(--sp4) 0;
}

/* ========================
   卡片辅助（正文内 card）
======================== */
.content-body .card {
  background: var(--c-gray-100);
  border-radius: var(--radius);
  padding: var(--sp4);
  margin-bottom: var(--sp3);
  transition: box-shadow var(--transition);
}
.content-body .card:hover {
  box-shadow: 0 4px 16px rgba(0,0,0,0.10);
}

/* ========================
   Focus 可访问性
======================== */
:focus-visible {
  outline: 2px solid var(--c-black);
  outline-offset: 2px;
}

button[aria-expanded]{min-width:44px;min-height:44px}