/* ===== 变量与基础 ===== */
:root {
  --color-primary: #2563eb; /* 科技蓝主色 */
  --color-primary-dark: #1d4ed8;
  --color-primary-light: #60a5fa;
  --color-accent: #06b6d4; /* 蓝绿高光 */
  --color-accent-light: #22d3ee;
  --color-dark: #020617;
  --color-dark-2: #0b1120;
  --color-text: #2d3748;
  --color-text-light: #718096;
  --color-bg: #f8fafc;
  --color-white: #ffffff;
  --font-sans: "Noto Sans SC", -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", sans-serif;
  --shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 10px 40px rgba(0, 0, 0, 0.12);
  --radius: 8px;
  --radius-lg: 12px;
  --header-h: 64px;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
  overflow-x: hidden;
}

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

ul {
  list-style: none;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ===== 顶部导航 ===== */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-h);
  background: rgba(26, 26, 46, 0.95);
  backdrop-filter: blur(12px);
  z-index: 1000;
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
}

.header-inner {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-weight: 700;
  font-size: 1rem;
  color: var(--color-white);
}

.logo-title {
  white-space: nowrap;
}

.nav {
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav-link {
  padding: 8px 14px;
  color: rgba(255, 255, 255, 0.85);
  font-size: 0.9rem;
  font-weight: 500;
  border-radius: var(--radius);
  transition: color 0.2s, background 0.2s;
}

.nav-link:hover,
.nav-link.active {
  color: var(--color-white);
  background: rgba(37, 99, 235, 0.3);
}

.btn-nav {
  margin-left: 12px;
  padding: 8px 20px !important;
  background: var(--color-primary) !important;
  color: var(--color-white) !important;
}

.btn-nav:hover {
  background: var(--color-primary-light) !important;
}

.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 6px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
}

.menu-toggle span {
  width: 24px;
  height: 2px;
  background: var(--color-white);
  border-radius: 1px;
}

/* ===== 按钮 ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 28px;
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 600;
  border-radius: var(--radius);
  border: none;
  cursor: pointer;
  transition: background 0.2s, color 0.2s, box-shadow 0.2s;
}

.btn-primary {
  background: var(--color-primary);
  color: var(--color-white);
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  box-shadow: 0 4px 16px rgba(196, 30, 58, 0.4);
}

.btn-outline {
  background: transparent;
  color: var(--color-white);
  border: 2px solid rgba(255, 255, 255, 0.8);
}

.btn-outline:hover {
  background: rgba(255, 255, 255, 0.15);
  border-color: var(--color-white);
}

.btn-lg {
  padding: 14px 32px;
  font-size: 1.05rem;
}

/* ===== Hero ===== */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding-top: var(--header-h);
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, var(--color-dark) 0%, var(--color-dark-2) 50%, #1e293b 100%);
  overflow: hidden;
}

#heroParticles {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
}

.hero-pattern {
  position: absolute;
  inset: 0;
  background-image: radial-gradient(circle at 20% 80%, rgba(37, 99, 235, 0.16) 0%, transparent 50%),
    radial-gradient(circle at 80% 20%, rgba(6, 182, 212, 0.18) 0%, transparent 40%);
  pointer-events: none;
}

.hero-content {
  position: relative;
  z-index: 1;
  text-align: center;
  color: var(--color-white);
}

.hero-slogan {
  font-size: 1.1rem;
  font-weight: 500;
  letter-spacing: 0.2em;
  color: var(--color-accent-light);
  margin-bottom: 12px;
}

.hero-title {
  font-size: clamp(1.8rem, 5vw, 2.8rem);
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 16px;
  text-shadow: 0 2px 20px rgba(0, 0, 0, 0.3);
}

.hero-desc {
  font-size: 1rem;
  color: rgba(255, 255, 255, 0.85);
  margin-bottom: 32px;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  justify-content: center;
}

.hero-scroll {
  position: absolute;
  bottom: 32px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  color: rgba(255, 255, 255, 0.6);
  font-size: 0.85rem;
}

.scroll-arrow {
  width: 24px;
  height: 24px;
  border-right: 2px solid currentColor;
  border-bottom: 2px solid currentColor;
  transform: rotate(45deg);
  animation: bounce 2s infinite;
}

@keyframes bounce {
  0%, 100% { transform: rotate(45deg) translateY(0); }
  50% { transform: rotate(45deg) translateY(6px); }
}

/* ===== 通用区块 ===== */
.section {
  padding: 80px 0;
}

.section-title {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--color-dark);
  text-align: center;
  margin-bottom: 8px;
}

.section-subtitle {
  text-align: center;
  color: var(--color-text-light);
  font-size: 0.95rem;
  margin-bottom: 48px;
}

/* ===== 大赛介绍 ===== */
.section-about {
  background: var(--color-white);
  box-shadow: var(--shadow);
}

.about-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
  margin-bottom: 40px;
}

.about-card {
  padding: 28px;
  background: var(--color-bg);
  border-radius: var(--radius-lg);
  text-align: center;
  border: 1px solid rgba(0, 0, 0, 0.06);
  transition: box-shadow 0.2s, transform 0.2s;
}

.about-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.about-icon {
  font-size: 2rem;
  margin-bottom: 12px;
}

.about-card h3 {
  font-size: 1.1rem;
  color: var(--color-primary);
  margin-bottom: 8px;
}

.about-card p {
  font-size: 0.95rem;
  color: var(--color-text);
}

.about-intro {
  max-width: 720px;
  margin: 0 auto;
  padding: 24px;
  background: linear-gradient(135deg, rgba(37, 99, 235, 0.08) 0%, rgba(6, 182, 212, 0.08) 100%);
  border-radius: var(--radius-lg);
  border-left: 4px solid var(--color-primary);
}

.about-intro p {
  color: var(--color-text);
  line-height: 1.8;
}

/* ===== 赛题设置 ===== */
.section-topics {
  background: var(--color-bg);
}

.topics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}

.topic-card {
  padding: 28px;
  background: var(--color-white);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  border-top: 4px solid var(--color-primary);
  transition: box-shadow 0.2s, transform 0.2s;
}

.topic-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.topic-num {
  display: inline-block;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-primary);
  opacity: 0.8;
  margin-bottom: 12px;
}

.topic-card h3 {
  font-size: 1.1rem;
  color: var(--color-dark);
  margin-bottom: 10px;
}

.topic-card p {
  font-size: 0.9rem;
  color: var(--color-text-light);
  line-height: 1.7;
}

/* ===== 奖项设置 ===== */
.section-awards {
  background: linear-gradient(180deg, var(--color-dark) 0%, var(--color-dark-2) 100%);
  color: var(--color-white);
}

.section-awards .section-title,
.section-awards .section-subtitle {
  color: var(--color-white);
}

.section-awards .section-subtitle {
  color: rgba(255, 255, 255, 0.7);
}

.awards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
}

.award-card {
  padding: 28px;
  background: rgba(255, 255, 255, 0.08);
  border-radius: var(--radius-lg);
  text-align: center;
  border: 1px solid rgba(255, 255, 255, 0.12);
  transition: background 0.2s, transform 0.2s;
}

.award-card:hover {
  background: rgba(255, 255, 255, 0.12);
  transform: scale(1.02);
}

.award-special {
  background: linear-gradient(135deg, rgba(37, 99, 235, 0.45) 0%, rgba(6, 182, 212, 0.3) 100%);
  border-color: var(--color-accent);
}

.award-name {
  display: block;
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.award-count {
  display: block;
  font-size: 0.95rem;
  opacity: 0.9;
  margin-bottom: 8px;
}

.award-money {
  display: block;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-accent-light);
}

/* ===== 报名表单 ===== */
.section-register {
  background: var(--color-white);
}

.register-wrap {
  max-width: 680px;
  margin: 0 auto;
}

.register-form {
  background: var(--color-bg);
  padding: 40px;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin-bottom: 20px;
}

.form-group {
  display: flex;
  flex-direction: column;
}

.form-group-full {
  grid-column: 1 / -1;
}

.form-group label {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--color-text);
  margin-bottom: 8px;
}

.form-group label span {
  color: var(--color-primary);
}

.form-group input,
.form-group select,
.form-group textarea {
  padding: 12px 14px;
  font-family: var(--font-sans);
  font-size: 1rem;
  border: 1px solid #e2e8f0;
  border-radius: var(--radius);
  background: var(--color-white);
  transition: border-color 0.2s, box-shadow 0.2s;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.18);
}

.form-group textarea {
  resize: vertical;
  min-height: 80px;
}

.btn-submit {
  width: 100%;
  margin-top: 16px;
  padding: 16px;
}

/* ===== 培训中心 ===== */
.section-training {
  background: var(--color-bg);
}

.training-content {
  max-width: 720px;
  margin: 0 auto;
}

.training-content > p {
  margin-bottom: 24px;
  line-height: 1.8;
  color: var(--color-text);
}

.training-tips {
  padding: 24px;
  background: var(--color-white);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  border-left: 4px solid var(--color-accent);
}

.training-tips h4 {
  font-size: 1.1rem;
  color: var(--color-dark);
  margin-bottom: 12px;
}

.training-tips ul {
  padding-left: 20px;
}

.training-tips li {
  position: relative;
  padding-left: 8px;
  margin-bottom: 8px;
  color: var(--color-text);
  list-style: disc;
}

/* ===== 通知公告 ===== */
.section-news {
  background: var(--color-white);
}

.news-list {
  max-width: 640px;
  margin: 0 auto;
}

.news-item {
  display: flex;
  align-items: center;
  gap: 20px;
  padding: 18px 0;
  border-bottom: 1px solid #e2e8f0;
  transition: background 0.2s;
}

.news-item:hover {
  background: var(--color-bg);
}

.news-date {
  flex-shrink: 0;
  font-size: 0.9rem;
  color: var(--color-text-light);
}

.news-title {
  font-weight: 500;
  color: var(--color-dark);
}

.news-title:hover {
  color: var(--color-primary);
}

/* ===== 联系我们 ===== */
.section-contact {
  background: var(--color-bg);
}

.contact-wrap {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  justify-content: center;
  gap: 48px;
  max-width: 720px;
  margin: 0 auto;
}

.contact-info p {
  margin-bottom: 12px;
  color: var(--color-text);
  line-height: 1.7;
}

.contact-qr {
  flex-shrink: 0;
}

.qr-placeholder {
  width: 160px;
  height: 160px;
  background: var(--color-white);
  border: 2px dashed #cbd5e1;
  border-radius: var(--radius);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 8px;
  color: var(--color-text-light);
  font-size: 0.9rem;
}

.qr-hint {
  font-size: 0.8rem;
  opacity: 0.8;
}

/* ===== 页脚 ===== */
.footer {
  background: var(--color-dark);
  color: rgba(255, 255, 255, 0.85);
  padding: 40px 0;
  text-align: center;
}

.footer-slogan {
  font-size: 1rem;
  color: var(--color-accent-light);
  margin-bottom: 8px;
}

.footer-title {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 12px;
}

.footer-copy {
  font-size: 0.85rem;
  color: rgba(255, 255, 255, 0.6);
}

/* ===== 响应式 ===== */
@media (max-width: 900px) {
  .nav {
    display: none;
  }

  .menu-toggle {
    display: flex;
  }

  .nav.open {
    display: flex;
    position: fixed;
    top: var(--header-h);
    left: 0;
    right: 0;
    bottom: 0;
    flex-direction: column;
    align-items: stretch;
    padding: 24px;
    background: var(--color-dark);
    gap: 0;
  }

  .nav.open .nav-link {
    padding: 16px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
  }

  .nav.open .btn-nav {
    margin: 24px 0 0;
  }

  .form-row {
    grid-template-columns: 1fr;
  }

  .contact-wrap {
    flex-direction: column;
    align-items: center;
  }
}

@media (max-width: 600px) {
  .section {
    padding: 56px 0;
  }

  .hero-actions {
    flex-direction: column;
  }

  .hero-actions .btn {
    width: 100%;
  }

  .register-form {
    padding: 24px;
  }

  .about-grid,
  .topics-grid {
    grid-template-columns: 1fr;
  }

  .awards-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}