:root {
  --entry-bg: #020609;
  --entry-ink: #eaf2f0;
  --entry-muted: #748388;
  --entry-ice: #b9d9db;
  --entry-blue: #6e9bb2;
  --entry-line: rgba(185, 217, 219, .2);
  --entry-mono: 'DM Mono', 'SFMono-Regular', Consolas, monospace;
}

* { box-sizing: border-box; }
html,
body { height: 100%; margin: 0; min-height: 100%; }
body {
  background: var(--entry-bg);
  color: var(--entry-ink);
  font-family: 'Noto Sans SC', 'Microsoft YaHei', sans-serif;
  overflow: hidden;
  width: 100%;
}
a { color: inherit; text-decoration: none; }

/* 入口页是独立的视口画布，任何元素都不依赖文档流计算垂直位置。 */
.entry-world {
  background:
    radial-gradient(circle at 50% 48%, rgba(91, 139, 158, .12), transparent 23%),
    linear-gradient(180deg, #020609 0%, #071116 70%, #020609 100%);
  height: 100vh;
  height: 100dvh;
  isolation: isolate;
  inset: 0;
  overflow: hidden;
  position: fixed;
  width: 100vw;
}
.entry-world::before {
  background: radial-gradient(ellipse at 50% 100%, rgba(101, 146, 154, .18), transparent 53%);
  bottom: -30%;
  content: '';
  height: 65%;
  left: 5%;
  pointer-events: none;
  position: absolute;
  width: 90%;
  z-index: 0;
}
.entry-particles {
  height: 100%;
  inset: 0;
  pointer-events: none;
  position: absolute;
  width: 100%;
  z-index: 1;
}
.entry-source {
  background: radial-gradient(circle, rgba(218, 239, 235, .42) 0, rgba(162, 204, 207, .16) 13%, rgba(92, 139, 157, .06) 34%, transparent 70%);
  border-radius: 50%;
  height: min(52vw, 620px);
  left: 50%;
  opacity: .7;
  pointer-events: none;
  position: absolute;
  top: 48%;
  transform: translate(-50%, -50%) scale(.72);
  transition: opacity .7s ease, transform 1.1s cubic-bezier(.7, 0, .2, 1);
  width: min(52vw, 620px);
  z-index: 2;
}
.entry-source::before {
  border: 1px solid rgba(185, 217, 219, .25);
  border-radius: 50%;
  content: '';
  inset: 31%;
  position: absolute;
}
.entry-source::after {
  background: linear-gradient(90deg, transparent, rgba(218, 239, 235, .28), transparent);
  content: '';
  height: 1px;
  left: 8%;
  position: absolute;
  top: 50%;
  width: 84%;
}
.entry-vignette {
  background: radial-gradient(ellipse, transparent 38%, rgba(0, 3, 5, .84) 100%);
  inset: 0;
  pointer-events: none;
  position: absolute;
  z-index: 3;
}

.entry-header,
.entry-footer {
  align-items: center;
  display: flex;
  font: 9px var(--entry-mono);
  justify-content: space-between;
  left: clamp(24px, 5vw, 72px);
  letter-spacing: .1em;
  position: fixed;
  right: clamp(24px, 5vw, 72px);
  text-transform: uppercase;
  z-index: 20;
}
.entry-header { top: 34px; }
.entry-footer { bottom: 29px; color: var(--entry-muted); }
.entry-brand { align-items: center; display: flex; gap: 11px; }
.entry-brand img {
  filter: drop-shadow(0 0 9px rgba(185, 217, 219, .5));
  height: 28px;
  width: 28px;
}
.entry-brand span {
  color: var(--entry-ink);
  font-family: 'Noto Sans SC', sans-serif;
  font-size: 13px;
  font-weight: 800;
  letter-spacing: .1em;
}
.entry-code { color: var(--entry-muted); }
.entry-footer a { color: var(--entry-muted); text-decoration: none; transition: color .2s ease; }
.entry-footer a:hover, .entry-footer a:focus-visible { color: var(--entry-ink); outline: none; }

/* 中心内容使用 viewport 坐标，按钮始终是标题信息之后的正常子项。 */
.entry-center {
  align-items: center;
  display: flex;
  flex-direction: column;
  left: 50%;
  max-width: 700px;
  position: fixed;
  text-align: center;
  top: 48%;
  transform: translate(-50%, -50%);
  width: min(700px, 90vw);
  z-index: 10;
}
.entry-core {
  align-items: center;
  background: radial-gradient(circle, rgba(185, 217, 219, .12), transparent 68%);
  border: 1px solid rgba(185, 217, 219, .28);
  border-radius: 50%;
  box-shadow: 0 0 42px rgba(110, 155, 178, .12);
  display: flex;
  height: clamp(128px, 18vw, 210px);
  justify-content: center;
  margin: 0 0 24px;
  position: relative;
  width: clamp(128px, 18vw, 210px);
}
.entry-core img {
  filter: drop-shadow(0 0 10px rgba(185, 217, 219, .42));
  height: 46%;
  width: 46%;
}
.entry-orbit { display: none; }
.entry-description {
  color: var(--entry-ice);
  font-size: 15px;
  line-height: 1.8;
  margin: 0 0 27px;
  text-shadow: 0 0 18px rgba(185, 217, 219, .24);
}
.entry-enter {
  align-items: center;
  border: 1px solid var(--entry-line);
  display: grid;
  font-size: 17px;
  justify-items: center;
  min-height: 58px;
  padding: 14px 20px;
  position: relative;
  text-align: center;
  width: min(300px, 80vw);
  transition: background .3s ease, border-color .3s ease, transform .3s ease;
}
.entry-enter::before {
  background: linear-gradient(90deg, transparent, rgba(185, 217, 219, .12), transparent);
  content: '';
  inset: 0;
  opacity: 0;
  position: absolute;
  transition: opacity .3s ease;
}
.entry-enter span {
  position: relative;
  z-index: 1;
}
.entry-enter strong {
  color: var(--entry-ice);
  font: 22px/1 var(--entry-mono);
  font-weight: 400;
  position: absolute;
  right: 18px;
  z-index: 1;
}
.entry-enter:hover {
  background: rgba(185, 217, 219, .08);
  border-color: rgba(185, 217, 219, .7);
  transform: translateY(-3px);
}
.entry-enter:hover::before { opacity: 1; }

/* 点击后保持入口的空间关系，只让中心光源短暂收束。 */
body.is-leaving .entry-source {
  opacity: .92;
  transform: translate(-50%, -50%) scale(1.32);
  transition: opacity .85s ease, transform 1.25s cubic-bezier(.16, 1, .3, 1);
}
body.is-leaving .entry-center { transform: translate(-50%, -50%); }
body.is-leaving .entry-description,
body.is-leaving .entry-enter {
  opacity: 0;
  transform: translateY(8px);
  transition: opacity .28s ease, transform .28s ease;
}
body.is-leaving .entry-core {
  opacity: .22;
  transform: scale(.86);
  transition: opacity .55s ease, transform .7s cubic-bezier(.16, 1, .3, 1);
}

@media (max-width: 640px) {
  .entry-header { top: 25px; }
  .entry-footer { bottom: 21px; }
  .entry-code,
  .entry-footer span:first-child { display: none; }
  .entry-center { top: 47%; }
  .entry-description { font-size: 12px; }
  .entry-enter { font-size: 16px; padding: 15px 18px; }
}
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after { animation: none !important; transition: none !important; }
  .entry-particles { opacity: .3; }
  .entry-enter:hover { transform: none; }
}