:root {
  --bg-top: #eef6ff;
  --bg-bottom: #d7e8ff;
  --panel: rgba(255, 255, 255, 0.82);
  --panel-border: rgba(18, 57, 99, 0.12);
  --ink: #15304d;
  --muted: #55708d;
  --accent: #0f766e;
  --accent-strong: #0d9488;
  --shadow: 0 24px 60px rgba(19, 48, 77, 0.18);
  --beam: #38bdf8;
  --beam-glow: #7dd3fc;
  --plate: #15304d;
  --b-symbol: #9333ea;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Trebuchet MS", "Gill Sans", "Segoe UI", sans-serif;
  color: var(--ink);
  background:
    radial-gradient(circle at top left, rgba(255,255,255,0.85), transparent 30%),
    linear-gradient(180deg, var(--bg-top), var(--bg-bottom));
}

.page {
  width: min(1360px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 1.5rem 0 2rem;
}

.mono { font-family: "Courier New", monospace; }
.muted { color: var(--muted); }
.hidden { display: none !important; }

/* ── Hero ───────────────────────────────────────────────── */
.hero {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 1.5rem;
  margin-bottom: 1rem;
  flex-wrap: wrap;
}

.hero-link {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  margin-bottom: 0.75rem;
  padding: 0.45rem 0.8rem;
  border-radius: 999px;
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--ink);
  background: rgba(255,255,255,0.9);
  border: 1px solid rgba(21,48,77,0.12);
}
.hero-link:hover { background: white; }

.eyebrow {
  margin: 0 0 0.35rem;
  color: var(--accent-strong);
  font-size: 0.9rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1 {
  margin: 0;
  font-size: clamp(1.8rem, 4vw, 3rem);
  line-height: 0.95;
}

.intro {
  max-width: 68ch;
  margin: 0.6rem 0 0;
  color: var(--muted);
  font-size: 1rem;
}

/* ── Layout ─────────────────────────────────────────────── */
.layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(280px, 320px);
  gap: 1rem;
  align-items: start;
}

.panel {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 24px;
  box-shadow: var(--shadow);
  backdrop-filter: blur(16px);
}

.main-col {
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

/* ── Apparatus ──────────────────────────────────────────── */
.apparatus-panel {
  padding: 1rem 1.2rem 1.2rem;
}

.apparatus-svg-wrap {
  width: 100%;
  background: linear-gradient(180deg, rgba(239,247,255,0.6), rgba(215,232,255,0.4));
  border-radius: 16px;
  padding: 0.4rem;
  border: 1px solid rgba(21,48,77,0.06);
}

#apparatus {
  display: block;
  width: 100%;
  height: auto;
}

/* SVG element styles */
.tube-glass {
  fill: rgba(220,235,250,0.45);
  stroke: rgba(21,48,77,0.28);
  stroke-width: 1.5;
}

.apparatus-label {
  font: 600 11px "Trebuchet MS", "Segoe UI", sans-serif;
  fill: var(--ink);
}
.apparatus-label.muted { fill: var(--muted); font-weight: 500; }

.filament-coil {
  fill: none;
  stroke: #ff6b3d;
  stroke-width: 2.2;
  stroke-linecap: round;
}
.filament-glow {
  fill: #ff6b3d;
  opacity: 0.22;
}

.anode {
  stroke: var(--ink);
  stroke-width: 3;
  stroke-linecap: round;
}

.plate {
  fill: var(--plate);
  transition: fill 0.15s;
}
.plate.charged-pos { fill: #c2410c; }
.plate.charged-neg { fill: #1d4ed8; }

.plate-sign {
  font: 700 16px "Cambria Math", Cambria, serif;
  fill: var(--ink);
  opacity: 0;
  transition: opacity 0.15s;
}
.plate-sign.show { opacity: 1; }

.dim {
  stroke: var(--muted);
  stroke-width: 1;
  fill: none;
}
.dim-label {
  font: italic 12px "Cambria Math", Cambria, serif;
  fill: var(--muted);
  stroke: none;
}

.b-sym {
  stroke: var(--b-symbol);
  stroke-width: 1.2;
  fill: none;
}
.b-sym-dot { fill: var(--b-symbol); stroke: none; }

.screen-bg {
  fill: rgba(120,200,140,0.18);
  stroke: #2d8a4a;
  stroke-width: 1.4;
}
.screen-grid line {
  stroke: rgba(45,138,74,0.45);
  stroke-width: 0.5;
}
.screen-grid .screen-grid-major {
  stroke: #2d8a4a;
  stroke-width: 1;
}

#beam-path {
  stroke: var(--beam-glow);
  stroke-width: 2;
  opacity: 0.95;
  filter: drop-shadow(0 0 2.5px var(--beam)) drop-shadow(0 0 5px rgba(56,189,248,0.55));
  transition: opacity 0.1s;
}

#beam-spot {
  fill: #86efac;
  filter: drop-shadow(0 0 4px #4ade80) drop-shadow(0 0 9px rgba(74,222,128,0.7));
}

#beam-spot.hidden { display: none; }

/* ── Controls ───────────────────────────────────────────── */
.controls {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.85rem;
  margin-top: 0.85rem;
}

.ctrl {
  padding: 0.7rem 0.85rem 0.55rem;
  background: rgba(239,247,255,0.7);
  border: 1px solid rgba(21,48,77,0.08);
  border-radius: 12px;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.ctrl-head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 0.5rem;
}

.ctrl label {
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--ink);
}

.ctrl-val {
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--ink);
}

.ctrl-val-wrap {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
}

input[type="number"].ctrl-val {
  width: 5.5rem;
  padding: 0.2rem 0.4rem;
  border: 1.5px solid rgba(21,48,77,0.2);
  border-radius: 7px;
  background: rgba(255,255,255,0.85);
  font: inherit;
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--ink);
  text-align: right;
  font-variant-numeric: tabular-nums;
  -moz-appearance: textfield;
}
input[type="number"].ctrl-val::-webkit-outer-spin-button,
input[type="number"].ctrl-val::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}
input[type="number"].ctrl-val:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
  background: white;
}

.ctrl-unit {
  font-size: 0.85rem;
  color: var(--muted);
}

.ctrl input[type="range"] {
  width: 100%;
  accent-color: var(--accent);
  cursor: pointer;
}

.ctrl-foot {
  display: flex;
  justify-content: space-between;
  font-size: 0.72rem;
}

/* ── Data column ────────────────────────────────────────── */
.data-col {
  padding: 1rem 1.15rem;
  position: sticky;
  top: 1rem;
  max-height: calc(100vh - 2rem);
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.data-title, .data-subtitle {
  margin: 0;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--muted);
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.readings-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}

.readings-table td {
  padding: 0.4rem 0.3rem;
  border-bottom: 1px solid rgba(21,48,77,0.06);
  vertical-align: middle;
}
.readings-table tr:last-child td { border-bottom: 0; }

.readings-table td:first-child {
  color: var(--muted);
  font-size: 0.86rem;
  padding-right: 0.6rem;
}

.readings-table td.mono {
  text-align: right;
  font-weight: 700;
  font-size: 0.92rem;
}

.readings-table .constant-row td:first-child {
  font-style: italic;
}
.readings-table .constant-row td.mono {
  color: var(--muted);
  font-weight: 600;
}

.constants-card {
  padding: 0.75rem 0.9rem;
  background: rgba(239,247,255,0.7);
  border: 1px solid rgba(21,48,77,0.06);
  border-radius: 12px;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

/* ── Responsive ─────────────────────────────────────────── */
@media (max-width: 1100px) {
  .layout { grid-template-columns: 1fr; }
  .data-col { position: static; max-height: none; }
}

@media (max-width: 760px) {
  .hero { flex-direction: column; align-items: flex-start; }
  .controls { grid-template-columns: 1fr; }
}