#boot {
  position: absolute;   /* 不是 fixed —— 要被 .device-frame 框住 */
  inset: 0;
  z-index: 9999;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: var(--c-surface);      /* 必须有背景色，否则透出后面的主屏幕 */
  overflow: hidden;
  transition: opacity 0.5s var(--ease);
}
#boot.hidden {
  opacity: 0;
  pointer-events: none;
}

/* 极淡的网点纹理，让纯色底不那么"死" */
#boot::before {
  content: '';
  position: absolute;
  inset: 0;
  pointer-events: none;
  opacity: 0.55;
  background-image:
    radial-gradient(circle, rgba(122, 116, 120, 0.035) 0 0.7px, transparent 0.8px);
  background-size: 5px 5px;
}

.boot-center {
  position: relative;
  z-index: 1;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* 标题与进度线的共同容器，宽度锁死 */
.boot-logo {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.boot-title {
  margin: 0;
  font-family: var(--font-display);
  font-size: 40px;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--c-text);
  display: flex;
  align-items: center;
  /* 预留高度，避免网络字体加载完成时标题跳动 */
  min-height: 52px;
  line-height: 52px;
  white-space: nowrap;
  transform-origin: center center;
  will-change: transform, opacity;
}

/* 收束：绕中心压扁 + 收字距 + 极轻模糊，透明度归零交给线层 */
#boot.is-morphing .boot-title {
  transform: scaleY(0.06);
  letter-spacing: -0.05em;
  filter: blur(1.5px);
  opacity: 0;
  transition:
    transform 320ms cubic-bezier(0.4, 0, 0.2, 1),
    letter-spacing 320ms cubic-bezier(0.4, 0, 0.2, 1),
    filter 320ms cubic-bezier(0.4, 0, 0.2, 1),
    opacity 200ms cubic-bezier(0.4, 0, 0.2, 1) 140ms;
}

/* 进度线轨道：与标题同中心，初始不可见并收在中间 */
.boot-progress {
  position: absolute;
  left: 0;
  right: 0;
  top: 50%;
  height: 3px;
  margin-top: -1.5px;
  border-radius: 2px;
  background: rgba(58, 58, 58, 0.12);
  overflow: hidden;
  opacity: 0;
  transform: scaleX(0.12);
  transform-origin: center center;
  pointer-events: none;
}

/* 标题压缩的最后阶段展开，接管视觉 */
#boot.is-morphing .boot-progress {
  opacity: 1;
  transform: scaleX(1);
  transition:
    opacity 140ms var(--ease) 160ms,
    transform 200ms cubic-bezier(0.4, 0, 0.2, 1) 140ms;
}

/* 填充层：只动 scaleX，原点在左边，方向永远是左 → 右 */
.boot-progress-fill {
  width: 100%;
  height: 100%;
  border-radius: inherit;
  background: var(--c-text);
  transform: scaleX(0);
  transform-origin: left center;
  will-change: transform;
}
#boot.is-loading .boot-progress-fill {
  transform: scaleX(1);
  transition: transform 900ms cubic-bezier(0.22, 1, 0.36, 1);
}
/* 完成后锁住满格，避免淡出期间回弹 */
#boot.is-complete .boot-progress-fill {
  transform: scaleX(1);
}

/* --- 减弱动态效果：跳过压扁/模糊，直接显示满格细线再快速淡出 --- */
@media (prefers-reduced-motion: reduce) {
  #boot {
    transition: opacity 0.2s var(--ease);
  }
  #boot.is-morphing .boot-title {
    transform: none;
    letter-spacing: 0.02em;
    filter: none;
    opacity: 0;
    transition: none;
  }
  #boot.is-morphing .boot-progress {
    opacity: 1;
    transform: none;
    transition: none;
  }
  #boot.is-loading .boot-progress-fill {
    transform: scaleX(1);
    transition: none;
  }
}