/* ===================================================
   NATIONAL TEST CENTER STYLESHEET (nation.css)
   =================================================== */

/* Reset & Basics */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html, body {
  min-height: 100%;
  overflow-x: hidden;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: #333;
  background-color: #ffffff;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* 1. 100vh Hero Banner */
.hero-banner {
  width: 100%;
  height: 100vh;
  overflow: hidden;
  background-color: #1a1a1a;
}

.banner-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

/* 主容器 */
.nation-container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 90px 30px 120px 30px;
}

/* 头部主标题与居中渐变分割线 */
.section-header {
  text-align: center;
  margin-bottom: 50px;
}

.section-title {
  font-size: 2.3rem;
  font-weight: 300;
  color: #2b2b2b;
  margin-bottom: 20px;
  letter-spacing: -0.5px;
}

.center-gradient-divider {
  position: relative;
  width: 100%;
  height: 1px;
  background-color: #eaedf1;
  margin: 0 auto;
}

.center-gradient-divider::before {
  content: "";
  position: absolute;
  left: 50%;
  top: -1.5px;
  transform: translateX(-50%);
  width: 120px;
  height: 4px;
  border-radius: 2px;
  background: linear-gradient(90deg, #c81e3a 0%, #5b1a7d 50%, #1b2685 100%);
}

/* ===================================================
   SECTION 1: HERO FEATURE & FLOATING BUBBLE
   =================================================== */
.hero-feature-section {
  margin-bottom: 40px;
  width: 100%;
}

.feature-hero-card {
  position: relative;
  width: 100%;
  border-radius: 20px;
  overflow: hidden;
  box-shadow: 0 12px 36px rgba(0, 0, 0, 0.08);
  background-color: #f7f9fc;
}

.feature-hero-img {
  width: 100%;
  height: auto;
  display: block;
  object-fit: cover;
}

/* 底部圆角白底气泡（与图片底部及两侧留有间隙） */
.floating-bubble {
  position: absolute;
  bottom: 24px;
  left: 24px;
  right: 24px;
  background: rgba(255, 255, 255, 0.98);
  backdrop-filter: blur(10px);
  border-radius: 16px;
  padding: 20px 48px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
}

.bubble-item {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 20px;
}

.bubble-text {
  display: flex;
  flex-direction: column;
}

.bubble-title {
  font-size: 1.45rem;
  font-weight: 500;
  color: #222222;
  margin-bottom: 4px;
  letter-spacing: -0.3px;
}

.bubble-sub {
  font-size: 0.85rem;
  color: #666666;
  font-weight: 300;
}

.bubble-icon {
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-left: 20px;
}

.bubble-icon-img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
}

.bubble-divider {
  width: 1px;
  height: 48px;
  background-color: #e5e8ed;
  margin: 0 10px;
}

/* ===================================================
   SECTION 2: ALTERNATING GRID (4 列双行交替)
   =================================================== */
.alternating-grid-section {
  width: 100%;
}

.matrix-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
  width: 100%;
}

.matrix-card {
  width: 100%;
  aspect-ratio: 1 / 1;
  border-radius: 18px;
  overflow: hidden;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.06);
}

/* 图片卡片 */
.card-photo {
  background-color: #f7f7f7;
}

.matrix-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

/* 跨两列宽图 */
.card-span-2 {
  grid-column: span 2;
  aspect-ratio: 2 / 1;
}

/* 渐变文本卡片 */
.card-gradient {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  color: #ffffff;
  padding: 24px 20px;
  transition: transform 0.25s ease, box-shadow 0.25s ease;
}

.card-gradient:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 28px rgba(0, 0, 0, 0.12);
}

/* 渐变色调 */
.card-red {
  background: linear-gradient(180deg, #c81e3a 0%, #880922 100%);
}

.card-purple {
  background: linear-gradient(180deg, #4f1b80 0%, #300c54 100%);
}

.card-magenta {
  background: linear-gradient(180deg, #881958 0%, #500d44 100%);
}

.matrix-icon-box {
  width: 52px;
  height: 52px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 12px;
}

.matrix-icon-img {
  max-width: 100%;
  max-height: 100%;
  object-fit: contain;
  display: block;
}

.matrix-title {
  font-size: 1.55rem;
  font-weight: 500;
  line-height: 1.2;
  margin-bottom: 6px;
  letter-spacing: -0.3px;
}

.matrix-desc {
  font-size: 0.8rem;
  font-weight: 300;
  line-height: 1.35;
  opacity: 0.95;
}

/* ===================================================
   RESPONSIVE DESIGN (响应式适配)
   =================================================== */
@media (max-width: 1024px) {
  .floating-bubble {
    padding: 16px 24px;
  }

  .bubble-title {
    font-size: 1.2rem;
  }

  .matrix-grid {
    gap: 16px;
  }

  .matrix-title {
    font-size: 1.3rem;
  }
}

@media (max-width: 768px) {
  .hero-banner {
    height: 70vh;
  }

  .nation-container {
    padding: 50px 16px 80px 16px;
  }

  .section-title {
    font-size: 1.8rem;
  }

  /* 气泡移动端转为竖直折叠 */
  .floating-bubble {
    position: static;
    margin-top: 16px;
    flex-direction: column;
    gap: 16px;
    padding: 20px;
    border-radius: 14px;
  }

  .bubble-item {
    width: 100%;
    padding: 0;
  }

  .bubble-divider {
    width: 100%;
    height: 1px;
    margin: 0;
  }

  /* 矩阵网格转为双列 */
  .matrix-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 14px;
  }

  .card-span-2 {
    grid-column: span 2;
    aspect-ratio: 16 / 9;
  }
}