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

html, body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
}

.container {
  max-width: 640px;
  margin: 0 auto;
  padding: 20px;
}

/* ========== 顶部标题栏 ========== */
.header-bar {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 24px;
}

.back-btn {
  color: white;
  text-decoration: none;
  font-size: 20px;
  padding: 6px 14px;
  background: rgba(255,255,255,0.2);
  border-radius: 8px;
  transition: background 0.3s;
  flex-shrink: 0;
}

.back-btn:hover {
  background: rgba(255,255,255,0.35);
}

.page-title {
  color: white;
  font-size: 22px;
  font-weight: 700;
  text-shadow: 0 2px 8px rgba(0,0,0,0.2);
}

/* ========== 简介卡片 ========== */
.intro-card {
  background: white;
  border-radius: 16px;
  padding: 28px 24px;
  margin-bottom: 20px;
  box-shadow: 0 10px 40px rgba(0,0,0,0.15);
  text-align: center;
}

.intro-card h1 {
  font-size: 20px;
  color: #1a1a2e;
  line-height: 1.5;
  margin-bottom: 12px;
}

.intro-desc {
  font-size: 14px;
  color: #666;
  line-height: 1.7;
}

/* ========== 步骤卡片 ========== */
.step-card {
  background: white;
  border-radius: 16px;
  padding: 22px 24px;
  margin-bottom: 16px;
  box-shadow: 0 8px 30px rgba(0,0,0,0.12);
}

.step-header {
  display: flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 14px;
}

.step-num {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  font-size: 18px;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.step-title {
  font-size: 17px;
  font-weight: 700;
  color: #1a1a2e;
}

.step-body {
  font-size: 15px;
  color: #444;
  line-height: 1.8;
}

.step-body p {
  margin-bottom: 10px;
}

.step-body p:last-child {
  margin-bottom: 0;
}

.step-body strong {
  color: #1a1a2e;
}

/* ========== 信息卡片 ========== */
.info-card {
  background: white;
  border-radius: 16px;
  padding: 22px 24px;
  margin-bottom: 16px;
  box-shadow: 0 8px 30px rgba(0,0,0,0.12);
  display: flex;
  gap: 16px;
  align-items: flex-start;
}

.info-icon {
  font-size: 32px;
  flex-shrink: 0;
  margin-top: 2px;
}

.info-content h3 {
  font-size: 16px;
  font-weight: 700;
  color: #1a1a2e;
  margin-bottom: 10px;
}

.info-content p {
  font-size: 14px;
  color: #555;
  line-height: 1.8;
  margin-bottom: 8px;
}

.info-content p:last-child {
  margin-bottom: 0;
}

.info-content strong {
  color: #1a1a2e;
}

/* ========== 流程图区域 ========== */
.flowchart-section {
  background: white;
  border-radius: 16px;
  padding: 24px;
  margin-bottom: 30px;
  box-shadow: 0 10px 40px rgba(0,0,0,0.15);
}

.flowchart-header {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 12px;
}

.flowchart-icon {
  font-size: 24px;
}

.flowchart-header h2 {
  font-size: 18px;
  color: #1a1a2e;
}

.flowchart-tip {
  font-size: 13px;
  color: #888;
  margin-bottom: 16px;
  line-height: 1.5;
}

.flowchart-img-wrap {
  border-radius: 12px;
  overflow: hidden;
  background: #f8f9fa;
  border: 1px solid #e5e7eb;
}

.flowchart-img {
  display: block;
  width: 100%;
  height: auto;
  cursor: zoom-in;
  transition: opacity 0.2s;
}

.flowchart-img:hover {
  opacity: 0.95;
}

/* ========== 图片预览遮罩 ========== */
.img-overlay {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 1000;
  align-items: center;
  justify-content: center;
  flex-direction: column;
}

.img-overlay.active {
  display: flex;
}

.img-overlay-bg {
  position: absolute;
  inset: 0;
  background: rgba(0,0,0,0.88);
}

.img-overlay-img {
  position: relative;
  z-index: 1;
  max-width: 92vw;
  max-height: 82vh;
  object-fit: contain;
  border-radius: 8px;
  cursor: zoom-out;
}

.img-overlay-hint {
  position: relative;
  z-index: 1;
  color: rgba(255,255,255,0.7);
  font-size: 13px;
  margin-top: 12px;
}

/* ========== 响应式 ========== */
@media (max-width: 480px) {
  .container {
    padding: 12px;
  }

  .page-title {
    font-size: 18px;
  }

  .intro-card {
    padding: 20px 16px;
  }

  .intro-card h1 {
    font-size: 17px;
  }

  .step-card,
  .info-card,
  .flowchart-section {
    padding: 18px 16px;
    border-radius: 14px;
  }

  .step-title {
    font-size: 16px;
  }

  .step-body,
  .info-content p {
    font-size: 14px;
  }
}