/* ============================================================
   OS — Chapter 04 rebuild
   Rotating hexagon instrument + diagnostic panel
   ============================================================ */

.os {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
  border: 1px solid var(--line);
  background: var(--bg);
  position: relative;
  overflow: hidden;
}

.os::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    linear-gradient(var(--line) 1px, transparent 1px) 0 0 / 100% 80px,
    linear-gradient(90deg, var(--line) 1px, transparent 1px) 0 0 / 80px 100%;
  opacity: 0.25;
  pointer-events: none;
  mask-image: radial-gradient(ellipse at center, black 30%, transparent 75%);
}

/* ---------- instrument (top) ---------- */
.os-instrument {
  position: relative;
  padding: 24px 28px 28px;
  border-bottom: 1px solid var(--line);
}

.os-readout {
  display: flex;
  align-items: center;
  gap: 18px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-3);
  padding-bottom: 16px;
  border-bottom: 1px dashed var(--line);
  margin-bottom: 20px;
}
.os-readout-k { color: var(--ink-3); }
.os-readout-n {
  color: var(--signal);
  font-size: 13px;
  letter-spacing: 0.08em;
}
.os-readout-t {
  color: var(--ink);
  font-size: 12px;
  letter-spacing: 0.18em;
}
.os-readout-spacer { flex: 1; }

.os-toggle {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 5px 10px;
  border: 1px solid var(--line);
  background: transparent;
  cursor: pointer;
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.18em;
  color: var(--ink-2);
  transition: border-color 0.2s, color 0.2s;
}
.os-toggle:hover { border-color: var(--signal); color: var(--ink); }
.os-toggle-dot {
  width: 7px; height: 7px;
  border-radius: 50%;
  background: var(--signal);
  box-shadow: 0 0 8px var(--signal);
  transition: background 0.2s, box-shadow 0.2s, opacity 0.2s;
}
.os-toggle[aria-pressed="false"] .os-toggle-dot {
  background: var(--ink-3);
  box-shadow: none;
  opacity: 0.5;
}
.os-toggle[aria-pressed="false"] .os-toggle-txt::after {
  content: "";
}

.os-dial {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 10px 0 6px;
}
.os-dial-svg {
  width: 100%;
  max-width: 560px;
  height: auto;
  aspect-ratio: 1 / 1;
  display: block;
}

/* progress arc */
.os-progress {
  transition: stroke-dasharray 0.8s cubic-bezier(0.6, 0.02, 0.08, 1);
}

/* nodes */
.os-node {
  cursor: pointer;
  transition: opacity 0.3s;
}
.os-node:hover .os-node-dot { fill: var(--ink); }
.os-node-ring {
  transition: stroke 0.35s, stroke-width 0.35s, fill 0.35s;
}
.os-node-dot {
  transition: fill 0.35s, r 0.35s;
}
.os-node-glow {
  transition: opacity 0.5s;
}
.os-node-k,
.os-node-t {
  font-family: var(--mono);
  font-size: 9.5px;
  letter-spacing: 0.18em;
  fill: var(--ink-3);
  transition: fill 0.35s;
}
.os-node-k { font-size: 8.5px; opacity: 0.75; }

.os-node.on .os-node-ring {
  stroke: var(--signal);
  stroke-width: 2;
  fill: var(--bg);
}
.os-node.on .os-node-dot { fill: var(--signal); }
.os-node.on .os-node-glow { opacity: 0.55; }
.os-node.on .os-node-k { fill: var(--signal); }
.os-node.on .os-node-t { fill: var(--ink); }

/* orbit head */
.os-head {
  transition: transform 0.8s cubic-bezier(0.6, 0.02, 0.08, 1);
}
.os-head circle:first-child {
  filter: drop-shadow(0 0 8px var(--signal));
}

/* center readout */
.os-center-k {
  font-family: var(--mono);
  font-size: 9px;
  letter-spacing: 0.28em;
  fill: var(--ink-3);
}
.os-center-n {
  font-family: var(--serif);
  font-size: 34px;
  font-style: italic;
  fill: var(--signal);
}
.os-center-l {
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.26em;
  fill: var(--ink);
}

/* ---------- diagnostic panel (bottom) ---------- */
.os-panel {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  border-top: 1px solid var(--line);
}
.os-panel-col {
  padding: 28px 26px 30px;
  border-right: 1px solid var(--line);
  min-height: 220px;
  position: relative;
}
.os-panel-col:last-child { border-right: 0; }

.os-col-k {
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin-bottom: 18px;
}

.os-col-t {
  font-family: var(--serif);
  font-size: 24px;
  line-height: 1.2;
  color: var(--ink);
  margin-bottom: 12px;
  letter-spacing: -0.01em;
  text-wrap: pretty;
  transition: opacity 0.3s;
}
.os-col-sub {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--signal);
}

/* signal visualization area */
.os-vis {
  width: 100%;
  aspect-ratio: 2 / 1;
  min-height: 140px;
  max-height: 180px;
  border: 1px solid var(--line);
  background:
    linear-gradient(var(--line) 1px, transparent 1px) 0 0 / 100% 30px,
    linear-gradient(90deg, var(--line) 1px, transparent 1px) 0 0 / 25% 100%;
  background-color: rgba(255,255,255,0.01);
  position: relative;
  overflow: hidden;
  transition: opacity 0.3s;
}
.os-vis svg {
  width: 100%;
  height: 100%;
  display: block;
}
.os-vis-txt {
  font-family: var(--mono);
  font-size: 9.5px;
  letter-spacing: 0.12em;
  fill: var(--ink-3);
  text-transform: uppercase;
}
.os-vis-num {
  font-family: var(--serif);
  font-size: 18px;
  fill: var(--ink);
}
.os-vis-stroke {
  stroke: var(--signal);
  fill: none;
  stroke-width: 1.5;
}
.os-vis-dash {
  stroke: var(--signal);
  fill: none;
  stroke-width: 1;
  stroke-dasharray: 3 4;
  opacity: 0.55;
}

.os-col-deliv {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border: 1px solid var(--line);
  background: rgba(110,168,254,0.04);
  margin-bottom: 14px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.05em;
  color: var(--ink);
  transition: opacity 0.3s;
}
.os-deliv-icon { color: var(--signal); font-size: 13px; }
.os-deliv-name { text-transform: uppercase; letter-spacing: 0.12em; font-size: 10.5px; }

.os-col-body {
  font-size: 13.5px;
  line-height: 1.55;
  color: var(--ink-2);
  text-wrap: pretty;
  transition: opacity 0.3s;
}

/* fade transition when stage changes */
.os.is-swapping .os-col-t,
.os.is-swapping .os-col-sub,
.os.is-swapping .os-col-deliv,
.os.is-swapping .os-col-body,
.os.is-swapping .os-vis {
  opacity: 0.12;
}

/* ---------- responsive ---------- */
@media (max-width: 960px) {
  .os-panel { grid-template-columns: 1fr; }
  .os-panel-col {
    border-right: 0;
    border-bottom: 1px solid var(--line);
    min-height: 0;
    padding: 22px 20px 24px;
  }
  .os-panel-col:last-child { border-bottom: 0; }
  .os-instrument { padding: 18px 20px 22px; }
  .os-readout { gap: 10px; flex-wrap: wrap; font-size: 10px; }
  .os-dial-svg { max-width: 420px; }
  .os-col-t { font-size: 20px; }
  .os-vis { max-height: 160px; }
}
@media (max-width: 560px) {
  .os-node-k, .os-node-t { font-size: 8px; }
  .os-node-k { font-size: 7.5px; }
  .os-center-n { font-size: 26px; }
  .os-center-l { font-size: 9px; }
}