:root {
  --primary-color: #3498db;
  --danger-color: #e74c3c;
  --bg-color: #f5f7fa;
  --card-bg: #ffffff;
  --text-color: #333333;
  --text-muted: #7f8c8d;
  --card-shadow: 0 5px 15px rgba(0,0,0,0.08);
}
* { margin: 0; padding: 0; box-sizing: border-box; }
body {
  font-family: 'PingFang SC', 'Microsoft YaHei', sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.6;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 85vh;
  padding: 20px;
  transition: background-color 0.3s, color 0.3s;
}
.container {
  background-color: var(--card-bg);
  border-radius: 16px;
  box-shadow: var(--card-shadow);
  width: 100%;
  max-width: 550px;
  padding: 66px 32px;
  text-align: center;
  transition: background-color 0.3s, box-shadow 0.3s;
}
.error-icon {
  width: 80px;
  height: 80px;
  margin: 0 auto 24px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 40px;
  color: var(--danger-color);
}
.error-icon-svg { width: 1.07227em; height: 1em; vertical-align: middle; fill: currentcolor; overflow: hidden; font-size: 128px; }
.error-code { font-size: 14px; color: var(--text-muted); margin-bottom: 8px; letter-spacing: 1px; }
.error-title { font-size: 28px; font-weight: 600; margin-bottom: 16px; color: var(--text-color); }
.error-subtitle { font-size: 16px; color: var(--text-muted); margin-bottom: 24px; font-weight: 400; }
.error-subtitle.hidden { display: none; }
.countdown { font-size: 14px; color: var(--text-muted); margin-bottom: 24px; }
.btn {
  display: inline-block;
  background-color: #0052D9;
  color: white;
  border: none;
  border-radius: 8px;
  padding: 12px 28px;
  font-size: 16px;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.3s ease;
  text-decoration: none;
  box-shadow: 0 4px 12px rgba(52, 152, 219, 0.2);
}
.btn:hover { background-color: #0041b8; transform: translateY(-2px); box-shadow: 0 6px 16px rgba(52, 152, 219, 0.3); }
.btn:active { transform: translateY(0); box-shadow: 0 4px 8px rgba(52, 152, 219, 0.2); }
@media (max-width: 576px) {
  .container { padding: 32px 24px; }
  .error-icon { width: 70px; height: 70px; font-size: 32px; }
  .error-title { font-size: 24px; }
}