@font-face{
  font-family:'Manrope';
  src:url('../../../open-runtime/3ae11c49db0455a3cc33e37d380f20fdb8c7f8b41dc07625c177e3d87a9d6ae6/Manrope.ttf') format('truetype');
  font-weight:200 800;
  font-display:swap;
}
:root{
  --bg:#04070f;
  --ink:#e9e4d6;
  --ink-dim:rgba(233,228,214,.62);
  --ink-faint:rgba(233,228,214,.38);
  --gold:#c8a96b;
  --hairline:rgba(200,169,107,.28);
  --panel:rgba(6,10,20,.72);
  --sans:'Manrope','PingFang SC','Hiragino Sans GB','Microsoft YaHei','Noto Sans CJK SC',sans-serif;
}
*{box-sizing:border-box;margin:0;padding:0}
html,body{height:100%}
body{
  background:var(--bg);
  color:var(--ink);
  font-family:var(--sans);
  overflow:hidden;
  -webkit-font-smoothing:antialiased;
}
#stage{position:fixed;inset:0}
#stage canvas{display:block;width:100%;height:100%}

.hud{position:fixed;z-index:5;pointer-events:none}
.hud button,.hud a{pointer-events:auto}

/* ---------- title ---------- */
.hud-title{top:clamp(16px,3vh,34px);left:clamp(18px,3vw,44px);max-width:min(46ch,60vw)}
.hud-title h1{
  font-weight:300;font-size:clamp(20px,2.6vw,34px);
  letter-spacing:.14em;line-height:1.15;
}
.hud-title h1 .title-sep{color:var(--gold);margin:0 .3em;font-weight:200}
.subtitle{
  margin-top:.5em;font-size:clamp(11px,1.1vw,13px);
  color:var(--ink-dim);letter-spacing:.22em;font-weight:400;
}

/* ---------- language ---------- */
.hud-lang{top:clamp(16px,3vh,34px);right:clamp(18px,3vw,44px);display:flex;gap:8px}
.lang-btn{
  background:none;border:1px solid var(--hairline);color:var(--ink-dim);
  font-family:var(--sans);font-size:12px;letter-spacing:.1em;
  padding:5px 13px;border-radius:999px;cursor:pointer;
  transition:color .25s,border-color .25s,background .25s;
}
.lang-btn.is-on{color:var(--bg);background:var(--gold);border-color:var(--gold)}
.lang-btn:not(.is-on):hover{color:var(--ink);border-color:rgba(200,169,107,.55)}
.lang-btn:focus-visible,button:focus-visible,a:focus-visible{outline:1px solid var(--gold);outline-offset:2px}

/* ---------- explanation panel ---------- */
.hud-panel{
  left:clamp(18px,3vw,44px);bottom:clamp(96px,14vh,150px);
  width:min(400px,calc(100vw - 36px));
  background:var(--panel);
  border:1px solid rgba(200,169,107,.16);
  border-left:2px solid var(--gold);
  backdrop-filter:blur(6px);
  padding:16px 18px 13px;
}
.hud-panel h2{
  font-size:15px;font-weight:600;letter-spacing:.06em;margin-bottom:.55em;
}
.exp-body{font-size:13px;line-height:1.75;color:var(--ink-dim);font-weight:400}
.exp-body p+p{margin-top:.55em}
.exp-note{
  margin-top:.9em;padding-top:.8em;border-top:1px solid rgba(233,228,214,.1);
  font-size:11px;line-height:1.6;color:var(--ink-faint);
}
.exp-src{margin-top:.6em;font-size:10.5px;letter-spacing:.02em;color:rgba(200,169,107,.55)}

/* ---------- controls ---------- */
.hud-controls{
  left:clamp(18px,3vw,44px);bottom:clamp(18px,3vh,34px);
  display:flex;flex-wrap:wrap;gap:8px;max-width:min(560px,calc(100vw - 36px));
}
.hud-controls button{
  font-family:var(--sans);font-size:12.5px;letter-spacing:.08em;
  color:var(--ink-dim);background:rgba(8,13,24,.7);
  border:1px solid var(--hairline);border-radius:3px;
  padding:8px 15px;cursor:pointer;
  transition:color .2s,border-color .2s,background .2s;
}
.hud-controls button:hover{color:var(--ink);border-color:rgba(200,169,107,.6)}
.hud-controls button[aria-pressed="true"]{
  color:var(--bg);background:var(--gold);border-color:var(--gold);font-weight:600;
}

/* ---------- layer buttons ---------- */
.hud-layers{
  right:clamp(18px,3vw,44px);top:50%;transform:translateY(-50%);
  display:flex;flex-direction:column;gap:7px;width:198px;
}
.layer-btn{
  display:flex;align-items:center;gap:10px;text-align:left;
  font-family:var(--sans);font-size:12.5px;letter-spacing:.04em;line-height:1.3;
  color:var(--ink-dim);background:rgba(8,13,24,.66);
  border:1px solid rgba(233,228,214,.12);border-radius:3px;
  padding:9px 12px;cursor:pointer;
  transition:color .2s,border-color .2s,background .2s;
}
.layer-btn:hover{color:var(--ink);border-color:rgba(200,169,107,.5)}
.layer-btn[aria-pressed="true"]{
  color:var(--ink);background:rgba(200,169,107,.16);border-color:var(--gold);
}
.sw{width:10px;height:10px;border-radius:1px;flex:none}
.sw-envelope{background:#cbb98a}
.sw-helium{background:#8a6f45}
.sw-metallic{background:#5b6c7d}
.sw-core{background:#71463c}

/* ---------- footer ---------- */
.hud-foot{
  right:clamp(18px,3vw,44px);bottom:clamp(18px,3vh,34px);
  display:flex;flex-wrap:wrap;gap:4px 16px;justify-content:flex-end;
  max-width:min(360px,44vw);
}
.hud-foot a{
  font-size:10.5px;letter-spacing:.04em;color:var(--ink-faint);
  text-decoration:none;border-bottom:1px solid rgba(233,228,214,.14);
  padding-bottom:1px;transition:color .2s,border-color .2s;
}
.hud-foot a:hover{color:var(--gold);border-color:var(--gold)}

#loading{
  position:fixed;inset:0;z-index:20;display:flex;align-items:center;justify-content:center;
  background:var(--bg);color:var(--ink-dim);font-size:13px;letter-spacing:.3em;
  transition:opacity .6s;
}
#loading.done{opacity:0;pointer-events:none}

/* ---------- mobile: dedicated 3D viewport on top, content scrolls below ---------- */
@media (max-width:760px){
  html,body{height:auto}
  body{overflow-x:hidden;overflow-y:auto;display:flex;flex-direction:column}
  #stage{
    position:relative;inset:auto;flex:none;
    width:100%;height:clamp(300px,42vh,360px);
  }
  #stage canvas{position:absolute;left:0;top:0}
  /* title + language float over the sky at the top of the viewport area */
  .hud{position:static}
  .hud-title{
    position:absolute;top:14px;left:14px;z-index:6;
    max-width:calc(100vw - 140px);
  }
  .hud-title h1{font-size:20px;letter-spacing:.1em}
  .subtitle{font-size:10.5px;letter-spacing:.14em;margin-top:.35em}
  .hud-lang{position:absolute;top:14px;right:14px;z-index:6}
  /* long explanation, layers, controls and sources flow below the 3D region */
  .hud-panel{
    order:2;width:auto;margin:10px 12px 0;padding:13px 14px;
    background:rgba(6,10,20,.92);backdrop-filter:none;
  }
  .exp-body{font-size:12.5px}
  .exp-note{font-size:10.5px}
  .hud-layers{
    order:3;transform:none;margin:10px 12px 0;width:auto;
    display:flex;flex-direction:row;flex-wrap:wrap;gap:6px;
  }
  .layer-btn{flex:1 1 44%;font-size:11.5px;padding:9px 10px}
  .hud-controls{order:4;margin:10px 12px 2px;max-width:none}
  .hud-controls button{padding:8px 11px;font-size:11.5px}
  .hud-foot{
    order:5;margin:10px 12px calc(18px + env(safe-area-inset-bottom,0px));
    max-width:none;justify-content:flex-start;
  }
  #loading{position:fixed}
}
@media (prefers-reduced-motion:reduce){
  .lang-btn,.hud-controls button,.layer-btn,.hud-foot a{transition:none}
}