/* ========================================
   照片说 / Photo Think — Landing Page
   设计原则：
   · 白底 + 大量留白
   · 纯黑文字 + 猫作为视觉主角
   · 强调色 = 珊瑚橙 #FF6B47（仅点缀）
   · 无标签、无药丸、无多余线条
   · 全屏滚动（scroll-snap）
   ======================================== */

/* ---------- 基础重置 ---------- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  scroll-snap-type: y mandatory;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'PingFang SC',
               'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  font-weight: 400;
  color: #0a0a0a;
  background: #ffffff;
  line-height: 1.4;
  overflow-x: hidden;
}

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

ul {
  list-style: none;
}

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

/* ---------- 顶部导航 ---------- */
.topnav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 24px 40px;
  font-size: 13px;
  font-weight: 500;
  letter-spacing: 0.01em;
  background: rgba(255, 255, 255, 0);
  transition: background 0.3s ease, border-color 0.3s ease;
  border-bottom: 1px solid transparent;
}

.topnav.is-scrolled {
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: saturate(180%) blur(12px);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
  border-bottom-color: rgba(10, 10, 10, 0.06);
}

.topnav__logo {
  font-weight: 600;
  letter-spacing: -0.01em;
}

.topnav__menu {
  display: flex;
  align-items: center;
  gap: 32px;
}

.topnav__menu a {
  position: relative;
  transition: opacity 0.2s ease;
}

.topnav__menu a:hover {
  opacity: 0.55;
}

/* ---------- 通用 Screen（每屏 = 一屏） ---------- */
.screen {
  position: relative;
  min-height: 100vh;
  padding: 120px 80px 80px;
  scroll-snap-align: start;
  scroll-snap-stop: always;
  display: flex;
  align-items: center;
  overflow: hidden;
}

/* 统一猫的容器：所有屏都是 360 × 240 */
.cat-slot {
  flex: 0 0 360px;
  width: 360px;
  height: 240px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.cat-slot img {
  width: 100%;
  height: 100%;
  object-fit: contain;
}

/* ---------- 第 1 屏 · Hero ---------- */
.screen--hero {
  flex-direction: row;
  justify-content: space-between;
  gap: 60px;
}

.hero__title {
  flex: 1 1 auto;
  font-size: clamp(36px, 4.2vw, 64px);
  font-weight: 600;
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: #0a0a0a;
  align-self: flex-start;
  padding-top: 10vh;
}

.hero__title .line {
  display: block;
  white-space: nowrap;
}

.hero__cat {
  flex: 0 0 360px;
  width: 360px;
  height: 240px;
  display: flex;
  align-items: center;
  justify-content: center;
  align-self: flex-end;
  padding-bottom: 10vh;
}

.hero__cat img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  filter: drop-shadow(0 20px 40px rgba(0, 0, 0, 0.04));
}

.hero__scroll {
  position: absolute;
  bottom: 48px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  font-size: 12px;
  color: #6b6b6b;
  letter-spacing: 0.05em;
  transition: color 0.2s ease;
}

.hero__scroll:hover {
  color: #0a0a0a;
}

.hero__scroll-arrow {
  font-size: 14px;
  animation: bounceDown 2.4s ease-in-out infinite;
}

@keyframes bounceDown {
  0%, 100% { transform: translateY(0); opacity: 0.6; }
  50%      { transform: translateY(6px); opacity: 1; }
}

/* ---------- 第 2 屏 · Story ---------- */
.screen--story {
  justify-content: space-between;
  align-items: stretch;
  gap: 60px;
}

.story__copy {
  flex: 1 1 auto;
  align-self: flex-start;
  padding-top: 10vh;
}

.story__line {
  font-size: clamp(32px, 3.6vw, 52px);
  font-weight: 600;
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: #0a0a0a;
}

.story__line .line {
  display: block;
  white-space: nowrap;
}

.story__cat {
  flex: 0 0 360px;
  width: 360px;
  height: 240px;
  display: flex;
  align-items: center;
  justify-content: center;
  align-self: flex-end;
  padding-bottom: 10vh;
}

.story__cat img {
  width: 100%;
  height: 100%;
  object-fit: contain;
}

/* ---------- 第 3 屏 · Capabilities ---------- */
.screen--capabilities {
  justify-content: space-between;
  align-items: stretch;
  gap: 60px;
}

.cap__copy {
  flex: 1 1 auto;
  align-self: flex-start;
  padding-top: 10vh;
}

.cap__line {
  font-size: clamp(32px, 3.6vw, 52px);
  font-weight: 600;
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: #0a0a0a;
}

.cap__line .line {
  display: block;
  white-space: nowrap;
}

.cap__cat {
  flex: 0 0 360px;
  width: 360px;
  height: 240px;
  display: flex;
  align-items: center;
  justify-content: center;
  align-self: flex-end;
  padding-bottom: 10vh;
}

.cap__cat img {
  width: 100%;
  height: 100%;
  object-fit: contain;
}

/* ---------- 第 4 屏 · Scenes ---------- */
.screen--scenes {
  justify-content: space-between;
  align-items: stretch;
  gap: 60px;
}

.scenes__copy {
  flex: 1 1 auto;
  align-self: flex-start;
  padding-top: 10vh;
}

.scenes__line {
  font-size: clamp(32px, 3.6vw, 52px);
  font-weight: 600;
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: #0a0a0a;
  margin-bottom: 32px;
}

.scenes__line .line {
  display: block;
  white-space: nowrap;
}

.scenes__list {
  display: flex;
  flex-wrap: wrap;
  gap: 12px 18px;
  font-size: 15px;
  font-weight: 400;
  color: #6b6b6b;
}

.scenes__list li::after {
  content: " /";
  margin-left: 18px;
  color: #d4d4d4;
}

.scenes__list li:last-child::after {
  content: "";
  margin-left: 0;
}

.scenes__cat {
  flex: 0 0 360px;
  width: 360px;
  height: 240px;
  display: flex;
  align-items: center;
  justify-content: center;
  align-self: flex-end;
  padding-bottom: 10vh;
}

.scenes__cat img {
  width: 100%;
  height: 100%;
  object-fit: contain;
}

/* ---------- 第 5 屏 · Download ---------- */
.screen--download {
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  gap: 36px;
  padding-bottom: 120px;
}

.dl__cat {
  width: 360px;
  height: 240px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.dl__cat img {
  width: 100%;
  height: 100%;
  object-fit: contain;
}

.dl__copy {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 20px;
}

.dl__line {
  font-size: clamp(28px, 3.2vw, 44px);
  font-weight: 600;
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: #0a0a0a;
}

.dl__sub {
  font-size: 15px;
  color: #6b6b6b;
  margin-top: -4px;
}

.dl__cta {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  padding: 14px 28px;
  background: #0a0a0a;
  color: #ffffff;
  border-radius: 12px;
  transition: transform 0.2s ease, background 0.2s ease;
  margin-top: 8px;
}

.dl__cta:hover {
  transform: translateY(-2px);
  background: #ff6b47;
}

.dl__cta-icon {
  width: 24px;
  height: 24px;
  background: #ffffff;
  -webkit-mask: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24'><path d='M17.05 20.28c-.98.95-2.05.8-3.08.35-1.09-.46-2.09-.48-3.24 0-1.44.62-2.2.44-3.06-.35C2.79 15.25 3.51 7.59 9.05 7.31c1.35.07 2.29.74 3.08.8 1.18-.24 2.31-.93 3.57-.84 1.51.12 2.65.72 3.4 1.8-3.12 1.87-2.38 5.98.48 7.13-.57 1.5-1.31 2.99-2.54 4.09zM12.03 7.25c-.15-2.23 1.66-4.07 3.74-4.25.29 2.58-2.34 4.5-3.74 4.25z'/></svg>") no-repeat center / contain;
          mask: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24'><path d='M17.05 20.28c-.98.95-2.05.8-3.08.35-1.09-.46-2.09-.48-3.24 0-1.44.62-2.2.44-3.06-.35C2.79 15.25 3.51 7.59 9.05 7.31c1.35.07 2.29.74 3.08.8 1.18-.24 2.31-.93 3.57-.84 1.51.12 2.65.72 3.4 1.8-3.12 1.87-2.38 5.98.48 7.13-.57 1.5-1.31 2.99-2.54 4.09zM12.03 7.25c-.15-2.23 1.66-4.07 3.74-4.25.29 2.58-2.34 4.5-3.74 4.25z'/></svg>") no-repeat center / contain;
}

.dl__cta-text {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  line-height: 1.1;
}

.dl__cta-text small {
  font-size: 10px;
  font-weight: 400;
  letter-spacing: 0.02em;
  opacity: 0.85;
}

.dl__cta-text strong {
  font-size: 18px;
  font-weight: 600;
  letter-spacing: -0.01em;
}

/* ---------- Footer ---------- */
.footer {
  padding: 32px 40px 40px;
  border-top: 1px solid rgba(10, 10, 10, 0.06);
  font-size: 12px;
  color: #6b6b6b;
  display: flex;
  flex-direction: column;
  gap: 12px;
  scroll-snap-align: start;
}

.footer__row {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
}

.footer__row--links a {
  transition: color 0.2s ease;
}

.footer__row--links a:hover {
  color: #0a0a0a;
}

.footer__brand {
  font-weight: 600;
  color: #0a0a0a;
}

.footer__sep {
  color: #d4d4d4;
}

/* ---------- 响应式 ---------- */
@media (max-width: 900px) {
  .topnav {
    padding: 18px 24px;
    font-size: 12px;
  }

  .screen {
    padding: 100px 32px 60px;
  }

  .screen--hero,
  .screen--story,
  .screen--capabilities,
  .screen--scenes {
    flex-direction: column;
    align-items: flex-start;
    gap: 40px;
  }

  .hero__cat,
  .story__cat,
  .cap__cat,
  .scenes__cat {
    width: 280px;
    height: 187px;
    flex: 0 0 280px;
    align-self: center;
  }

  .dl__cat {
    width: 280px;
    height: 187px;
  }
}

@media (max-width: 480px) {
  .hero__title { font-size: 32px; }
  .story__line,
  .cap__line,
  .scenes__line { font-size: 28px; }
  .dl__line { font-size: 24px; }
}

/* ---------- 滚动渐入动效 ---------- */
.screen > * {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.8s ease, transform 0.8s ease;
}

.screen.is-visible > * {
  opacity: 1;
  transform: translateY(0);
}

.screen > *:nth-child(2) { transition-delay: 0.1s; }
.screen > *:nth-child(3) { transition-delay: 0.2s; }