/* ── Reset ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

/* ── Design tokens ── */
:root {
  --bg:          #121417;
  --surface:     #1b1e24;
  --surface-alt: #22262e;
  --border:      #2c3038;
  --border-warm: #3a3229;
  --text:        #e4e5e9;
  --text-muted:  #878c99;
  --amber:       #e8a838;
  --amber-dim:   #c78820;
  --amber-glow:  rgba(232, 168, 56, 0.10);
  --ember:       #d45a20;
  --ember-glow:  rgba(212, 90, 32, 0.08);
  --radius:      14px;
  --radius-sm:   8px;
  --shadow:      0 2px 24px rgba(0,0,0,.35);
}

html { scroll-behavior: smooth; }
body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

.container { max-width: 1120px; margin: 0 auto; padding: 0 24px; }

/* ── Header ── */
header {
  position: relative;
  overflow: hidden;
  padding: 56px 0 48px;
  text-align: center;
  background: linear-gradient(180deg, #241b1b 0%, var(--bg) 100%);
  border-bottom: 1px solid var(--border);
}
.header-glow {
  position: absolute;
  top: -80px;
  left: 50%;
  transform: translateX(-50%);
  width: 600px;
  height: 260px;
  border-radius: 50%;
  background: radial-gradient(ellipse, rgba(200,40,40,0.14) 0%, transparent 70%);
  pointer-events: none;
}
.brand-logo {
  display: block;
  margin: 0 auto 16px;
  height: 32px;
  width: auto;
  object-fit: contain;
}
header h1 {
  font-family: 'Poppins', sans-serif;
  font-size: 2.4rem;
  font-weight: 700;
  letter-spacing: -0.5px;
  color: var(--text);
  line-height: 1.2;
}
.subtitle {
  color: var(--text-muted);
  margin-top: 10px;
  font-size: 1rem;
  font-weight: 400;
}

/* ── Cards ── */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 36px 40px;
  margin: 28px 0;
  box-shadow: var(--shadow);
  position: relative;
}
.card h2 {
  font-family: 'Poppins', sans-serif;
  font-size: 1.35rem;
  font-weight: 600;
  line-height: 1.3;
}
.card-desc {
  color: var(--text-muted);
  margin-top: 4px;
  font-size: 0.9rem;
  line-height: 1.5;
}
.step-row {
  display: flex;
  align-items: flex-start;
  gap: 18px;
  margin-bottom: 28px;
}
.step-num {
  flex-shrink: 0;
  width: 38px;
  height: 38px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-weight: 700;
  font-size: 0.95rem;
  color: #fff;
  background: #c0392b;
  box-shadow: 0 0 18px rgba(192,57,43,0.15), 0 0 0 4px rgba(192,57,43,0.08);
  line-height: 1;
}

/* ── Forms ── */
.form-row { display: flex; gap: 20px; flex-wrap: wrap; }
.form-group { flex: 1; min-width: 180px; margin-bottom: 8px; }
.form-group label {
  display: block;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 6px;
  text-transform: uppercase;
  letter-spacing: 0.6px;
}
select, input[type="number"] {
  width: 100%;
  padding: 11px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg);
  color: var(--text);
  font-family: inherit;
  font-size: 0.95rem;
  appearance: none;
  cursor: pointer;
  transition: border-color 0.2s, box-shadow 0.2s;
}
select:hover, input[type="number"]:hover { border-color: #3e4452; }
select:focus, input[type="number"]:focus {
  outline: none;
  border-color: var(--amber-dim);
  box-shadow: 0 0 0 3px var(--amber-glow);
}
select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%23878c99' stroke-width='2' fill='none'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 14px center;
  padding-right: 36px;
}

/* ── Cutout Layout (dims left, diagram right) ── */
.cutout-layout {
  display: grid;
  grid-template-columns: 180px 1fr;
  gap: 24px;
  align-items: start;
}
.dimensions-display {
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.dim-box {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 20px 18px;
  text-align: center;
  transition: border-color 0.2s;
}
.dim-box:hover { border-color: var(--border-warm); }
.dim-label {
  display: block;
  font-size: 0.7rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.8px;
  margin-bottom: 6px;
}
.dim-value {
  display: block;
  font-size: 1.65rem;
  font-weight: 700;
  color: var(--amber);
  font-variant-numeric: tabular-nums;
}

/* ── Cutout Diagram ── */
.cutout-diagram-wrapper { text-align: center; }
#cutout-diagram { width: 100%; max-height: 380px; }

/* ── Sliders ── */
.slider-row { display: flex; align-items: center; gap: 14px; }
input[type="range"] {
  flex: 1;
  -webkit-appearance: none;
  height: 5px;
  border-radius: 3px;
  background: var(--border);
  outline: none;
  transition: background 0.15s;
}
input[type="range"]:hover { background: #3a3e48; }
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 20px; height: 20px;
  border-radius: 50%;
  background: var(--amber);
  cursor: grab;
  box-shadow: 0 1px 6px rgba(0,0,0,.4), 0 0 12px var(--amber-glow);
  transition: transform 0.12s, box-shadow 0.12s;
  border: 2px solid rgba(255,255,255,0.12);
}
input[type="range"]::-webkit-slider-thumb:hover {
  box-shadow: 0 1px 6px rgba(0,0,0,.4), 0 0 20px rgba(232,168,56,0.25);
}
input[type="range"]::-webkit-slider-thumb:active { cursor: grabbing; transform: scale(1.12); }
input[type="range"]::-moz-range-thumb {
  width: 20px; height: 20px;
  border-radius: 50%;
  background: var(--amber);
  cursor: grab;
  border: 2px solid rgba(255,255,255,0.12);
}
.slider-value {
  min-width: 64px;
  text-align: right;
  font-weight: 700;
  font-size: 1rem;
  color: var(--amber);
  font-variant-numeric: tabular-nums;
}
.hint {
  font-size: 0.78rem;
  color: var(--text-muted);
  margin-top: 6px;
  line-height: 1.45;
}

/* ── Calculator layout ── */
.calculator-layout {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 28px;
  align-items: start;
}
.controls-panel { position: sticky; top: 24px; }

/* ── Result card ── */
.result-card {
  margin-top: 24px;
  padding: 22px 24px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--amber-dim);
  background: linear-gradient(135deg, rgba(232,168,56,0.06) 0%, rgba(212,90,32,0.04) 100%);
  position: relative;
  overflow: hidden;
}
.result-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--amber), var(--ember));
}
.result-label {
  display: block;
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.6px;
}
.result-value {
  display: block;
  font-family: 'Poppins', sans-serif;
  font-size: 2rem;
  font-weight: 700;
  color: var(--amber);
  margin: 6px 0 2px;
  line-height: 1.1;
}
.result-sub {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* ── Canvas ── */
.diagram-panel {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  overflow: hidden;
}
#light-diagram { width: 100%; height: auto; display: block; }

/* ── Formula note ── */
.formula-note {
  margin-top: 20px;
  padding: 0;
  font-size: 0.8rem;
  color: var(--text-muted);
  line-height: 1.5;
  font-style: italic;
}

/* ── Table ── */
.table-wrapper { overflow-x: auto; margin-top: 4px; }
table { width: 100%; border-collapse: collapse; font-size: 0.88rem; }
th, td {
  padding: 11px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border);
  white-space: nowrap;
}
th {
  color: var(--text-muted);
  font-weight: 600;
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.6px;
}
td { color: var(--text); }
tr:hover td { background: rgba(255,255,255,0.02); }

/* ── Footer ── */
footer {
  text-align: center;
  padding: 36px 0;
  color: var(--text-muted);
  font-size: 0.8rem;
  border-top: 1px solid var(--border);
  margin-top: 48px;
}

/* ── CTA Section ── */
.cta-section {
  text-align: center;
  padding: 48px 40px;
}
.cta-section h2 {
  font-size: 1.6rem;
  margin-bottom: 24px;
}
.cta-button {
  display: inline-block;
  padding: 14px 40px;
  background: #c0392b;
  color: #fff;
  font-family: 'Poppins', sans-serif;
  font-size: 1rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  text-decoration: none;
  transition: background 0.2s, box-shadow 0.2s;
  box-shadow: 0 2px 12px rgba(192,57,43,0.25);
}
.cta-button:hover {
  background: #a93226;
  box-shadow: 0 4px 20px rgba(192,57,43,0.35);
}
.cta-link {
  display: block;
  margin-top: 14px;
  color: var(--text-muted);
  font-size: 0.88rem;
  text-decoration: none;
  transition: color 0.2s;
}
.cta-link:hover {
  color: var(--text);
  text-decoration: underline;
}

/* ── Responsive ── */
@media (max-width: 800px) {
  .calculator-layout { grid-template-columns: 1fr; }
  .controls-panel { position: static; }
  .cutout-layout { grid-template-columns: 1fr; }
  .dimensions-display { flex-direction: row; flex-wrap: wrap; gap: 10px; }
  .dim-box { flex: 1; min-width: 100px; }
  header { padding: 36px 0 32px; }
  header h1 { font-size: 1.7rem; }
  .card { padding: 24px 20px; margin: 20px 0; }
  .step-row { gap: 14px; }
  .step-num { width: 32px; height: 32px; font-size: 0.85rem; }
  .dim-value { font-size: 1.3rem; }
  .result-value { font-size: 1.7rem; }
}

@media (max-width: 480px) {
  .container { padding: 0 16px; }
  .card { padding: 20px 16px; }
  .form-row { flex-direction: column; gap: 12px; }
  .dimensions-display { gap: 8px; }
  .dim-box { min-width: 80px; padding: 14px 8px; }
  .dim-value { font-size: 1.15rem; }
}