/* ============ Reciprocal Zenith Angles — UI ============ */
:root {
  --bg: #04060d;
  --panel: rgba(10, 16, 30, 0.78);
  --panel-border: rgba(120, 160, 220, 0.16);
  --text: #dbe4ff;
  --text-dim: #93a7c9;
  --cyan: #4cc9f0;     /* observer A */
  --amber: #ffb703;    /* observer B */
  --magenta: #f25ca2;  /* central angle θ */
  --green: #7ae582;
  --radius: 14px;
  font-size: 16px;
}
* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
html, body {
  margin: 0; padding: 0; width: 100%; height: 100%;
  overflow: hidden; background: var(--bg); color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}
#app { position: fixed; inset: 0; }
#scene { position: absolute; inset: 0; touch-action: none; }
#labels { position: absolute; inset: 0; pointer-events: none; overflow: hidden; }

/* 3D CSS2D labels */
.lbl { font-size: 0.8rem; color: var(--text); text-shadow: 0 1px 6px #000c; white-space: nowrap; }
.lbl.big { font-size: 1.05rem; font-weight: 700; letter-spacing: 0.06em; }
.lbl.a { color: var(--cyan); }
.lbl.b { color: var(--amber); }
.lbl.c { color: var(--magenta); }
.lbl.rf { color: var(--green); font-size: 0.74rem; }
.lbl.dim { color: var(--text-dim); font-size: 0.72rem; }
.lbl .deg { font-variant-numeric: tabular-nums; font-weight: 700; }

/* ---------- glass panels ---------- */
.glass {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  box-shadow: 0 10px 36px #0009;
}

/* ---------- header ---------- */
#hdr {
  position: absolute; top: 12px; left: 14px; z-index: 20;
  padding: 8px 14px; display: flex; align-items: center; gap: 10px;
  pointer-events: auto;
}
#hdr h1 {
  margin: 0; font-size: 0.92rem; font-weight: 800; letter-spacing: 0.10em;
  text-transform: uppercase;
  background: linear-gradient(90deg, var(--cyan), var(--amber));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
#hdr .sub { font-size: 0.68rem; color: var(--text-dim); letter-spacing: 0.04em; }
#btn-about {
  border: 1px solid var(--panel-border); background: transparent; color: var(--text-dim);
  width: 26px; height: 26px; border-radius: 50%; cursor: pointer; font-size: 0.85rem; line-height: 1;
}
#btn-about:hover { color: var(--text); border-color: var(--text-dim); }

/* ---------- equation banner ---------- */
#eq {
  position: absolute; top: 12px; left: 50%; transform: translateX(-50%); z-index: 19;
  padding: 10px 20px; font-size: 1.12rem; font-variant-numeric: tabular-nums;
  white-space: nowrap; text-align: center;
}
#eq .za { color: var(--cyan); font-weight: 700; }
#eq .zb { color: var(--amber); font-weight: 700; }
#eq .th { color: var(--magenta); font-weight: 700; }
#eq .rho { color: var(--green); font-weight: 700; }
#eq .sum { font-weight: 800; }
#eq small { display: block; font-size: 0.66rem; color: var(--text-dim); letter-spacing: 0.05em; margin-top: 2px; }
#eq .flash { animation: eqflash 0.9s ease; }
@keyframes eqflash { 0% { filter: brightness(2.2); } 100% { filter: brightness(1); } }

/* ---------- readouts ---------- */
#readouts {
  position: absolute; top: 86px; right: 14px; z-index: 18; width: 250px;
  padding: 12px 14px; font-size: 0.85rem;
}
#readouts h3 { margin: 0 0 8px; font-size: 0.66rem; letter-spacing: 0.14em; color: var(--text-dim); text-transform: uppercase; }
#readouts .row { display: flex; justify-content: space-between; padding: 2.5px 0; }
#readouts .row .k { color: var(--text-dim); }
#readouts .row .v { font-variant-numeric: tabular-nums; font-weight: 600; }
#readouts .row.hl .v { color: var(--green); }
#readouts .row .v.a { color: var(--cyan); } #readouts .row .v.b { color: var(--amber); } #readouts .row .v.th { color: var(--magenta); } #readouts .row .v.rf { color: var(--green); }
#readouts .divider { height: 1px; background: var(--panel-border); margin: 7px 0; }
#readouts .verdict { margin-top: 8px; font-size: 0.74rem; line-height: 1.45; color: var(--text-dim); }
#readouts .verdict b { color: var(--green); }
#readouts .verdict.bad b { color: #ff7b72; }

/* ---------- tour panel ---------- */
#tour {
  position: absolute; left: 14px; bottom: 14px; z-index: 21; width: 400px; max-width: calc(100vw - 28px);
  padding: 16px 18px 12px; pointer-events: auto;
}
#tour .step-tag { font-size: 0.64rem; letter-spacing: 0.16em; color: var(--cyan); text-transform: uppercase; margin-bottom: 4px; }
#tour h2 { margin: 0 0 8px; font-size: 1.18rem; }
#tour .body { font-size: 0.9rem; line-height: 1.55; color: #c4d2ee; min-height: 70px; }
#tour .body b { color: var(--text); }
#tour .body .a { color: var(--cyan); font-weight: 600; }
#tour .body .b { color: var(--amber); font-weight: 600; }
#tour .body .th { color: var(--magenta); font-weight: 600; }
#tour .body .num { font-variant-numeric: tabular-nums; font-weight: 700; color: var(--text); }
#tour .body .rf { color: var(--green); font-weight: 600; }
#tour .body .hint { display: block; margin-top: 8px; font-size: 0.78rem; color: var(--text-dim); font-style: italic; }
#tour nav { display: flex; align-items: center; gap: 10px; margin-top: 12px; }
#tour .dots { display: flex; gap: 5px; flex: 1; justify-content: center; flex-wrap: wrap; }
#tour .dots i { width: 7px; height: 7px; border-radius: 50%; background: #2c3c5c; cursor: pointer; transition: all 0.25s; }
#tour .dots i.on { background: var(--cyan); transform: scale(1.3); }
#tour .dots i.done { background: #4a6088; }
button.btn {
  border: 1px solid var(--panel-border); background: #16223a; color: var(--text);
  padding: 9px 16px; border-radius: 9px; cursor: pointer; font-size: 0.85rem; font-weight: 600;
  transition: background 0.2s, border-color 0.2s; min-height: 40px;
}
button.btn:hover { background: #1e2e4e; border-color: #3c5680; }
button.btn.primary { background: linear-gradient(135deg, #0e6b8c, #1287b1); border-color: #2ba3cf; }
button.btn.primary:hover { background: linear-gradient(135deg, #11799d, #18a0d0); }
button.btn:disabled { opacity: 0.35; cursor: default; }
#tour .skip { background: none; border: none; color: var(--text-dim); font-size: 0.72rem; cursor: pointer; padding: 6px; }
#tour .skip:hover { color: var(--text); }

/* ---------- controls panel ---------- */
#controls {
  position: absolute; right: 14px; bottom: 14px; z-index: 20; width: 280px;
  padding: 14px 16px; pointer-events: auto; max-height: calc(100svh - 380px); overflow-y: auto;
}
#controls h3 { margin: 0 0 10px; font-size: 0.66rem; letter-spacing: 0.14em; color: var(--text-dim); text-transform: uppercase; }
#controls .grp { margin-bottom: 12px; }
#controls label.sl { display: block; font-size: 0.76rem; color: var(--text-dim); margin-bottom: 3px; }
#controls label.sl .val { float: right; color: var(--text); font-variant-numeric: tabular-nums; font-weight: 600; }
input[type=range] { width: 100%; accent-color: var(--cyan); height: 28px; cursor: pointer; }
#controls .note { font-size: 0.7rem; color: var(--text-dim); line-height: 1.45; margin-top: 2px; }
#controls select {
  width: 100%; margin: 5px 0 4px; padding: 8px 10px; border-radius: 8px;
  border: 1px solid var(--panel-border); background: #131e34; color: var(--text);
  font-size: 0.76rem; font-weight: 600; cursor: pointer; color-scheme: dark;
}
#controls select:hover { border-color: #3c5680; }
#controls .note b { color: var(--text); font-variant-numeric: tabular-nums; }
.seg { display: flex; gap: 6px; flex-wrap: wrap; }
.seg button {
  flex: 1; min-width: 0; border: 1px solid var(--panel-border); background: #131e34; color: var(--text-dim);
  padding: 8px 4px; border-radius: 8px; cursor: pointer; font-size: 0.76rem; font-weight: 600; min-height: 38px;
}
.seg button.on { background: #1c4a66; color: #fff; border-color: var(--cyan); }
.seg button:hover { color: var(--text); }
.seg.mode button.on.flat { background: #5c3d12; border-color: var(--amber); }
.chk { display: flex; align-items: center; gap: 8px; font-size: 0.78rem; color: var(--text-dim); padding: 3px 0; cursor: pointer; }
.chk input { accent-color: var(--cyan); width: 16px; height: 16px; }
#controls .views .seg { margin-top: 4px; }

/* gear FAB (mobile) */
#fab {
  display: none; position: absolute; right: 14px; bottom: 14px; z-index: 40;
  width: 52px; height: 52px; border-radius: 50%; border: 1px solid var(--panel-border);
  background: var(--panel); color: var(--text); font-size: 1.3rem; cursor: pointer;
  backdrop-filter: blur(10px); -webkit-backdrop-filter: blur(10px);
}

/* ---------- first-person HUD ---------- */
#fphud { position: absolute; inset: 0; z-index: 15; pointer-events: none; display: none; }
#fphud .reticle {
  position: absolute; left: 50%; top: 50%; width: 26px; height: 26px; transform: translate(-50%, -50%);
  border: 1.5px solid rgba(255,255,255,0.55); border-radius: 50%;
}
#fphud .reticle::before, #fphud .reticle::after {
  content: ""; position: absolute; background: rgba(255,255,255,0.55);
}
#fphud .reticle::before { left: 50%; top: -8px; width: 1.5px; height: 8px; }
#fphud .reticle::after { top: 50%; left: -8px; height: 1.5px; width: 8px; }
.hudline { position: absolute; left: 0; width: 100%; height: 0; border-top: 1.5px dashed rgba(160, 200, 255, 0.75); }
.hudline .tag {
  position: absolute; left: 12px; top: -22px; font-size: 0.72rem; letter-spacing: 0.08em;
  color: #a8c8ff; background: #0a101ecc; padding: 2px 8px; border-radius: 6px;
}
.hudtarget { position: absolute; transform: translate(-50%, -50%); text-align: center; }
.hudtarget .ring { width: 38px; height: 38px; border: 2px solid var(--amber); border-radius: 50%; margin: 0 auto; box-shadow: 0 0 18px #ffb70366; }
.hudtarget .tag { font-size: 0.74rem; color: var(--amber); background: #0a101ecc; padding: 2px 8px; border-radius: 6px; margin-top: 4px; display: inline-block; }
.hudtrue { position: absolute; transform: translate(-50%, -50%); text-align: center; display: none; }
.hudtrue .ring { width: 30px; height: 30px; border: 1.6px dashed rgba(200, 215, 240, 0.55); border-radius: 50%; margin: 0 auto; }
.hudtrue .tag { font-size: 0.68rem; color: var(--text-dim); background: #0a101ecc; padding: 2px 7px; border-radius: 6px; margin-top: 3px; display: inline-block; }
#fphud .dip {
  position: absolute; right: 13%; width: 0; border-left: 2px solid var(--green);
}
#fphud .dip .tag {
  position: absolute; right: 8px; top: 50%; transform: translateY(-50%); font-size: 0.78rem; font-weight: 700;
  color: var(--green); background: #0a101ecc; padding: 3px 9px; border-radius: 6px; white-space: nowrap;
}
#fphud .who {
  position: absolute; top: 70px; left: 50%; transform: translateX(-50%);
  font-size: 0.8rem; letter-spacing: 0.1em; color: var(--text-dim); background: #0a101ecc; padding: 5px 14px; border-radius: 999px;
}
#fphud .who b { color: var(--cyan); }
#btn-exit-fp {
  display: none; position: absolute; top: 116px; left: 50%; transform: translateX(-50%); z-index: 22; pointer-events: auto;
}

/* ---------- intro & about overlays ---------- */
.overlay {
  position: fixed; inset: 0; z-index: 50; display: flex; align-items: center; justify-content: center;
  background: #03050bd9; backdrop-filter: blur(8px); -webkit-backdrop-filter: blur(8px);
  padding: 18px; overflow-y: auto;
}
.overlay .card { max-width: 620px; width: 100%; padding: 34px 36px; max-height: 90svh; overflow-y: auto; }
.overlay h2 {
  margin: 0 0 4px; font-size: 1.7rem;
  background: linear-gradient(90deg, var(--cyan), var(--amber));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.overlay .tagline { color: var(--text-dim); font-size: 0.82rem; letter-spacing: 0.12em; text-transform: uppercase; margin-bottom: 16px; }
.overlay p { line-height: 1.65; color: #c4d2ee; font-size: 0.95rem; }
.overlay p b { color: var(--text); }
.overlay .actions { display: flex; gap: 12px; margin-top: 22px; flex-wrap: wrap; }
.overlay .actions .btn { flex: 1; min-width: 160px; padding: 13px 18px; font-size: 0.95rem; }
.overlay h4 { margin: 18px 0 6px; color: var(--cyan); font-size: 0.95rem; }
.overlay .close-x {
  position: sticky; float: right; top: 0; border: none; background: none; color: var(--text-dim);
  font-size: 1.5rem; cursor: pointer; line-height: 1; padding: 0;
}
.hidden { display: none !important; }

/* ---------- toast ---------- */
#toast {
  position: absolute; bottom: 90px; left: 50%; transform: translateX(-50%); z-index: 40;
  padding: 10px 18px; font-size: 0.85rem; opacity: 0; transition: opacity 0.4s; pointer-events: none;
  max-width: 86vw; text-align: center;
}
#toast.show { opacity: 1; }

/* ---------- mobile ---------- */
@media (max-width: 920px) {
  :root { font-size: 15px; }
  #hdr { top: 8px; left: 8px; padding: 6px 10px; }
  #hdr .sub { display: none; }
  #eq {
    top: 48px; bottom: auto; left: 50%; transform: translateX(-50%);
    padding: 6px 10px; font-size: 0.78rem; width: max-content; max-width: calc(100vw - 16px);
  }
  #eq small { display: none; }
  #readouts {
    top: 92px; right: 8px; left: auto; width: 172px; padding: 9px 11px; font-size: 0.74rem;
  }
  #readouts .verdict { display: none; }
  #tour {
    left: 8px; right: 8px; bottom: calc(env(safe-area-inset-bottom, 0px) + 8px);
    width: auto; padding: 12px 14px 10px;
  }
  #tour .body { min-height: 0; font-size: 0.85rem; max-height: 30svh; overflow-y: auto; }
  #controls {
    right: 8px; left: 8px; bottom: calc(env(safe-area-inset-bottom, 0px) + 8px);
    width: auto; max-height: 62svh; display: none;
  }
  #controls.open { display: block; z-index: 35; }
  #fab { display: block; bottom: calc(env(safe-area-inset-bottom, 0px) + 14px); }
  #fab.tour-up { bottom: auto; top: 92px; left: 8px; right: auto; width: 44px; height: 44px; font-size: 1.05rem; }
  #fphud .who { top: 140px; }
  #fphud .who { top: 52px; font-size: 0.7rem; }
  #btn-exit-fp { top: 90px; }
  .overlay .card { padding: 24px 20px; }
}
@media (max-width: 920px) and (orientation: landscape) {
  #tour { left: 8px; right: auto; width: min(420px, 52vw); }
}