/* 全屏封面 */
#index-cover {
  position: fixed;
  top: 0; left: 0;
  width: 100vw; height: 100vh;
  z-index: 999;
  background: #000;
  transition: transform 0.6s ease;
}
.cover-bg {
  width: 100%; height: 100%;
  background: url('/images/cover.jpg') center/cover no-repeat;
  opacity: 0.8;
}
.cover-content {
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  text-align: center;
  color: #fff;
}
.site-title {
  font-size: 3rem;
  margin: 0;
}
.site-subtitle {
  font-size: 1.5rem;
  margin-top: 1rem;
  opacity: 0;
  animation: slideUp 1.8s forwards 0.6s;
}
.scroll-arrow {
  font-size: 2rem;
  margin-top: 2rem;
  animation: bounce 2s infinite;
}
@keyframes slideUp {
  from { transform: translateY(30px); opacity: 0; }
  to   { transform: translateY(0);   opacity: 1; }
}
@keyframes bounce {
  0%,100% { transform: translateY(0); }
  50%     { transform: translateY(8px); }
}
body.cover-mode .navbar {
  opacity: 0;
  transition: opacity 0.3s;
}
body.cover-mode.scrolled .navbar {
  opacity: 1;
}
@media (max-width: 768px) {
  .site-title { font-size: 2.2rem; }
  .site-subtitle { font-size: 1.2rem; }
}

.site-subtitle {
  font-size: 1.1rem;   /* 再小一点 */
  line-height: 1.4;    /* 行距舒服 */
  max-width: 90%;      /* 手机不超屏 */
  margin: 1rem auto 0;
  word-break: keep-all;
}

.site-subtitle {
  font-size: clamp(0.9rem, 2.8vw, 1.3rem); /* 随屏宽自动缩放 */
  max-width: 90vw;                         /* 不超屏 */
  margin: 1rem auto 0;
  white-space: nowrap;                     /* 强制不换行 */
  overflow: hidden;                        /* 保险 */
}