/* 首页 —— 黑白 · 星空 */

* { margin: 0; padding: 0; box-sizing: border-box; }

html, body {
  height: 100%;
  background: #000;
  color: #fff;
  overflow: hidden;                    /* 星空占满一屏，不出滚动条 */
  font-family: -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Microsoft YaHei', sans-serif;
  -webkit-font-smoothing: antialiased;
}

/* 星空画布铺满整个视口，永远在最底层 */
#sky {
  position: fixed;
  inset: 0;
  display: block;
  z-index: 0;
  pointer-events: none;                /* 星星不挡点击 */
}

/* ---------- 内容层 ---------- */

/* 标题靠上，按钮紧跟其下；两者背景都是透明的，
   所以看到的背景就是那片星空本身 */
.stage {
  position: relative;
  z-index: 1;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start;
  padding: 11vh 24px 40px;
  gap: 34px;
}

.welcome {
  font-size: clamp(22px, 4.6vw, 40px);
  font-weight: 300;
  letter-spacing: 0.22em;
  /* letter-spacing 会在最后一个字后面也留白，用等量缩进抵消，视觉才真正居中 */
  text-indent: 0.22em;
  text-align: center;
  text-shadow: 0 0 22px rgba(255, 255, 255, .4);
  animation: fade-in 2.4s ease both;
}

@keyframes fade-in {
  from { opacity: 0; letter-spacing: 0.5em; }
  to   { opacity: 1; letter-spacing: 0.22em; }
}

/* ---------- 按钮 ---------- */

.links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 14px;
  opacity: 0;
  animation: rise 1.1s ease 1.4s both;
}

@keyframes rise {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: none; }
}

.links a {
  display: inline-block;
  padding: 11px 30px;
  font-size: 14px;
  letter-spacing: 0.14em;
  text-indent: 0.14em;                 /* 同上，抵消字距造成的偏移 */
  color: #fff;
  text-decoration: none;
  border: 1px solid rgba(255, 255, 255, .45);
  border-radius: 999px;

  /* 关键：背景完全透明 —— 按钮里透出来的就是星空 */
  background: transparent;

  transition: background .25s, border-color .25s, box-shadow .25s;
}

.links a:hover {
  background: rgba(255, 255, 255, .12);
  border-color: #fff;
  box-shadow: 0 0 22px rgba(255, 255, 255, .25);
}

.links a:active {
  background: rgba(255, 255, 255, .22);
}

/* ---------- 移动端 ---------- */

@media (max-width: 480px) {
  .stage { padding-top: 9vh; gap: 26px; }
  .links { gap: 10px; }
  .links a { padding: 10px 22px; font-size: 13px; }
}

/* 尊重系统的「减少动态效果」设置 */
@media (prefers-reduced-motion: reduce) {
  .welcome, .links { animation: none; opacity: 1; transform: none; }
}