/* NEXUS — 开屏动画
   ---------------------------------------------------------------------------
   · 覆盖层固定在最上层，内容层（.shell）同时已经在渲染，所以动画永不阻塞。
   · 首次启动：--dur-splash（完整品牌动画）
   · 后续启动：.splash--fast（快速过渡）
   · 不提供跳过按钮：动画时长本身就是设计的一部分，且不可交互阻断
   · prefers-reduced-motion 下退化为一次淡入淡出
   -------------------------------------------------------------------------- */

.splash {
  position: fixed;
  inset: 0;
  z-index: var(--z-splash);
  display: grid;
  place-items: center;
  background: var(--splash-bg-top);
  opacity: 1;
  transition: opacity var(--dur-slow) var(--ease-out);
  will-change: opacity;
}

.splash__stage {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-5);
  transform: translateY(0);
}

/* ------------------------------------------------------------- 品牌标记 */
.splash__mark {
  position: relative;
  width: var(--splash-mark-size);
  height: var(--splash-mark-size);
  display: grid;
  place-items: center;
}

.splash__ring {
  position: absolute;
  inset: 0;
  border-radius: 50%;
  border: 1px solid var(--splash-ring);
  opacity: 0;
  transform: scale(0.55);
  animation: splash-ring var(--dur-splash) var(--ease-out) forwards;
}

.splash__ring--slow {
  border-color: var(--splash-ring-soft);
  animation-name: splash-ring-slow;
  animation-delay: 120ms;
}

.splash__core {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--color-ice-strong);
  opacity: 0;
  transform: scale(0.4);
  animation: splash-core var(--dur-splash) var(--ease-out) forwards;
}

@keyframes splash-ring {
  0%   { opacity: 0;   transform: scale(0.55); }
  35%  { opacity: 1;   transform: scale(0.92); }
  100% { opacity: 0.18; transform: scale(1.06); }
}

@keyframes splash-ring-slow {
  0%   { opacity: 0;   transform: scale(0.5); }
  45%  { opacity: 0.9; transform: scale(1.12); }
  100% { opacity: 0;   transform: scale(1.34); }
}

@keyframes splash-core {
  0%   { opacity: 0; transform: scale(0.3); }
  30%  { opacity: 1; transform: scale(1); }
  100% { opacity: 0.85; transform: scale(0.92); }
}

/* --------------------------------------------------------------- 字标 */
.splash__word {
  font-size: calc(var(--text-brand) * 1.1);
  font-weight: var(--weight-light);
  letter-spacing: calc(var(--tracking-brand) * 1.1);
  padding-left: calc(var(--tracking-brand) * 1.1); /* 补偿末字符字距 */
  color: var(--color-text);
  opacity: 0;
  animation: splash-word var(--dur-splash) var(--ease-out) forwards;
}

/* 只有位移与淡入：不做模糊「对焦」，那是相机语汇，不是工具语汇 */
@keyframes splash-word {
  0%   { opacity: 0; transform: translateY(4px); }
  45%  { opacity: 1; transform: translateY(0); }
  100% { opacity: 1; transform: translateY(0); }
}

/* --------------------------------------------------------- 进度细线 */
.splash__line {
  width: 132px;
  height: 1px;
  background: var(--splash-line);
  overflow: hidden;
}

.splash__line span {
  display: block;
  width: 100%;
  height: 100%;
  background: var(--color-ice);
  opacity: 0.55;
  transform: translateX(-100%);
  animation: splash-line var(--dur-splash) var(--ease-soft) forwards;
}

@keyframes splash-line {
  0%   { transform: translateX(-100%); }
  100% { transform: translateX(0); }
}

/* ------------------------------------------------------------- 状态字 */
.splash__status {
  font-family: var(--font-sans);
  font-size: var(--text-xs);
  letter-spacing: var(--tracking-label);
  color: var(--color-text-faint);
  opacity: 0;
  animation: splash-status var(--dur-splash) var(--ease-out) forwards;
}

@keyframes splash-status {
  0%, 25% { opacity: 0; }
  60%     { opacity: 1; }
  100%    { opacity: 0.55; }
}

/* --------------------------------------------------------- 快速过渡 */
/* 后续启动：动画压缩到 --dur-splash-fast，视觉上是同一套语汇的缩短版 */
html[data-boot="fast"] .splash__ring,
html[data-boot="fast"] .splash__core,
html[data-boot="fast"] .splash__word,
html[data-boot="fast"] .splash__status,
.splash--fast .splash__ring,
.splash--fast .splash__core,
.splash--fast .splash__word,
.splash--fast .splash__status { animation-duration: var(--dur-splash-fast); }

html[data-boot="fast"] .splash__line span,
.splash--fast .splash__line span { animation-duration: var(--dur-splash-fast); }

html[data-boot="fast"] .splash__ring--slow,
.splash--fast .splash__ring--slow { animation-delay: 40ms; }

/* --------------------------------------------------------------- 退场 */
.splash.is-leaving {
  opacity: 0;
  pointer-events: none;
}

.splash.is-done {
  display: none;
}

/* ------------------------------------------------- 减少动效偏好 */
@media (prefers-reduced-motion: reduce) {
  .splash__ring,
  .splash__ring--slow,
  .splash__core,
  .splash__word,
  .splash__line span,
  .splash__status {
    animation: none;
    opacity: 1;
    transform: none;
    filter: none;
  }
  .splash__line span { transform: none; }
  .splash { transition-duration: 120ms; }
}