:root {
  --gold:        #c9922a;
  --gold-light:  #e8b84b;
  --gold-pale:   #f5e6c0;
  --forge:       #0e0c09;
  --forge-2:     #161410;
  --forge-3:     #1e1b16;
  --forge-4:     #2a261e;
  --forge-5:     #3a3328;
  --ash:         #8a7f6e;
  --ash-light:   #b0a690;
  --cream:       #f0e8d8;
  --error:       #c0392b;
  --success:     #2d6a4f;
  --radius:      4px;
  --transition:  180ms ease;
}

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

html, body {
  height: 100%;
  background: var(--forge);
  color: var(--cream);
  font-family: 'Cormorant Garamond', Georgia, serif;
  font-size: 17px;
  line-height: 1.6;
}

/* ── Layout ── */
.app {
  display: grid;
  grid-template-columns: 260px 1fr;
  grid-template-rows: auto 1fr;
  min-height: 100vh;
}

/* ── Top bar ── */
.topbar {
  grid-column: 1 / -1;
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 0 28px;
  height: 60px;
  background: var(--forge-2);
  border-bottom: 1px solid var(--forge-5);
  position: sticky;
  top: 0;
  z-index: 100;
}

.topbar-logo {
  display: flex;
  align-items: center;
  gap: 10px;
}

.topbar-logo svg {
  width: 28px;
  height: 28px;
  fill: var(--gold);
}

.topbar-title {
  font-size: 1.5rem;
  font-weight: 500;
  letter-spacing: 0.04em;
  color: var(--cream);
}

.topbar-title span {
  color: var(--gold-light);
  font-style: italic;
}

.topbar-sub {
  margin-left: auto;
  font-size: 0.8rem;
  font-family: 'DM Mono', monospace;
  color: var(--ash);
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

/* ── Sidebar ── */
.sidebar {
  background: var(--forge-2);
  border-right: 1px solid var(--forge-5);
  padding: 24px 0;
  overflow-y: auto;
  position: sticky;
  top: 60px;
  height: calc(100vh - 60px);
}

.sidebar-section-label {
  padding: 6px 20px;
  font-family: 'DM Mono', monospace;
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--ash);
}

.tool-btn {
  display: flex;
  align-items: center;
  gap: 12px;
  width: 100%;
  padding: 11px 20px;
  background: transparent;
  border: none;
  cursor: pointer;
  text-align: left;
  color: var(--ash-light);
  font-family: 'Cormorant Garamond', serif;
  font-size: 1rem;
  font-weight: 400;
  transition: background var(--transition), color var(--transition);
  border-left: 2px solid transparent;
}

.tool-btn:hover {
  background: var(--forge-3);
  color: var(--cream);
}

.tool-btn.active {
  background: var(--forge-3);
  color: var(--gold-light);
  border-left-color: var(--gold);
}

.tool-btn-icon {
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  flex-shrink: 0;
}

.tool-btn-info {
  flex: 1;
  min-width: 0;
}

.tool-btn-name {
  display: block;
  font-weight: 500;
  line-height: 1.2;
}

.tool-btn-desc {
  display: block;
  font-size: 0.78rem;
  color: var(--ash);
  line-height: 1.3;
  margin-top: 1px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.tool-btn.active .tool-btn-desc {
  color: var(--ash-light);
}

.sidebar-divider {
  height: 1px;
  background: var(--forge-4);
  margin: 12px 0;
}

/* ── Main content ── */
.main {
  padding: 36px 44px;
  overflow-y: auto;
  max-width: 860px;
}

/* ── Tool panels ── */
.tool-panel {
  display: none;
  animation: fadeUp 220ms ease both;
}

.tool-panel.visible {
  display: block;
}

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(12px); }
  to   { opacity: 1; transform: translateY(0); }
}

.panel-header {
  margin-bottom: 28px;
  padding-bottom: 18px;
  border-bottom: 1px solid var(--forge-4);
}

.panel-title {
  font-size: 2rem;
  font-weight: 300;
  color: var(--cream);
  letter-spacing: 0.02em;
  line-height: 1.15;
}

.panel-title em {
  color: var(--gold-light);
  font-style: italic;
}

.panel-sub {
  margin-top: 6px;
  font-size: 0.9rem;
  font-family: 'DM Mono', monospace;
  color: var(--ash);
  letter-spacing: 0.04em;
}

/* ── Form elements ── */
.form-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin-bottom: 24px;
}

.form-grid.three-col {
  grid-template-columns: 1fr 1fr 1fr;
}

.form-row {
  display: flex;
  gap: 12px;
  margin-bottom: 20px;
  align-items: flex-end;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 7px;
}

.field.full { grid-column: 1 / -1; }

label {
  font-size: 0.72rem;
  font-family: 'DM Mono', monospace;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--ash-light);
}

input[type="number"],
select {
  background: var(--forge-3);
  border: 1px solid var(--forge-5);
  border-radius: var(--radius);
  color: var(--cream);
  font-family: 'DM Mono', monospace;
  font-size: 0.95rem;
  padding: 10px 13px;
  width: 100%;
  outline: none;
  transition: border-color var(--transition), box-shadow var(--transition);
  -webkit-appearance: none;
}

input[type="number"]:focus,
select:focus {
  border-color: var(--gold);
  box-shadow: 0 0 0 2px rgba(201, 146, 42, 0.15);
}

select option {
  background: var(--forge-3);
  color: var(--cream);
}

/* optgroup label in dark bg */
select optgroup {
  font-style: normal;
  font-weight: 600;
  color: var(--ash-light);
  background: var(--forge-4);
}

.unit-toggle {
  display: flex;
  border: 1px solid var(--forge-5);
  border-radius: var(--radius);
  overflow: hidden;
}

.unit-toggle button {
  flex: 1;
  padding: 10px 16px;
  background: var(--forge-3);
  border: none;
  color: var(--ash-light);
  font-family: 'DM Mono', monospace;
  font-size: 0.85rem;
  letter-spacing: 0.06em;
  cursor: pointer;
  transition: background var(--transition), color var(--transition);
}

.unit-toggle button.active {
  background: var(--gold);
  color: var(--forge);
  font-weight: 500;
}

.unit-toggle button:not(.active):hover {
  background: var(--forge-4);
  color: var(--cream);
}

/* ── Calculate button ── */
.btn-calc {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 32px;
  background: var(--gold);
  color: var(--forge);
  border: none;
  border-radius: var(--radius);
  font-family: 'Cormorant Garamond', serif;
  font-size: 1.05rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  cursor: pointer;
  transition: background var(--transition), transform 80ms;
  text-transform: uppercase;
}

.btn-calc:hover  { background: var(--gold-light); }
.btn-calc:active { transform: scale(0.98); }

/* ── Result card ── */
.result-card {
  margin-top: 28px;
  background: var(--forge-3);
  border: 1px solid var(--forge-5);
  border-radius: var(--radius);
  padding: 24px 28px;
  display: none;
  animation: fadeUp 220ms ease both;
}

.result-card.visible { display: block; }

.result-card.error {
  border-color: rgba(192, 57, 43, 0.4);
  background: rgba(192, 57, 43, 0.08);
}

.result-label {
  font-family: 'DM Mono', monospace;
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--ash);
  margin-bottom: 6px;
}

.result-weight {
  font-size: 3.2rem;
  font-weight: 300;
  color: var(--gold-light);
  letter-spacing: -0.01em;
  line-height: 1;
}

.result-weight sup {
  font-size: 1.2rem;
  vertical-align: super;
  color: var(--ash-light);
  font-style: italic;
}

.result-meta {
  margin-top: 18px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 14px;
}

.result-meta-item {
  background: var(--forge-4);
  border-radius: var(--radius);
  padding: 10px 14px;
}

.result-meta-item .label {
  font-family: 'DM Mono', monospace;
  font-size: 0.6rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--ash);
  display: block;
  margin-bottom: 3px;
}

.result-meta-item .value {
  font-size: 0.92rem;
  color: var(--cream);
}

.result-error-msg {
  color: #e74c3c;
  font-size: 0.95rem;
}

/* ── Density info table ── */
.alloy-table-wrap {
  margin-top: 36px;
}

.alloy-table-title {
  font-size: 1.1rem;
  font-weight: 400;
  color: var(--ash-light);
  margin-bottom: 14px;
  font-style: italic;
}

.alloy-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
}

.alloy-table th {
  font-family: 'DM Mono', monospace;
  font-size: 0.62rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--ash);
  text-align: left;
  padding: 8px 12px;
  border-bottom: 1px solid var(--forge-5);
}

.alloy-table td {
  padding: 7px 12px;
  border-bottom: 1px solid var(--forge-4);
  color: var(--cream);
  font-family: 'DM Mono', monospace;
  font-size: 0.84rem;
}

.alloy-table tr:last-child td { border-bottom: none; }

.alloy-table tbody tr:hover td {
  background: var(--forge-3);
}

.alloy-cat-header td {
  background: var(--forge-4) !important;
  color: var(--gold) !important;
  font-style: italic;
  font-family: 'Cormorant Garamond', serif;
  font-size: 0.92rem;
  letter-spacing: 0.04em;
  padding: 6px 12px;
}

/* ── Welcome screen ── */
.welcome {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  justify-content: center;
  min-height: 60vh;
  gap: 18px;
}

.welcome-ornament {
  font-size: 3rem;
  color: var(--gold);
  opacity: 0.6;
}

.welcome-title {
  font-size: 2.8rem;
  font-weight: 300;
  line-height: 1.1;
  color: var(--cream);
}

.welcome-title em {
  color: var(--gold-light);
  font-style: italic;
}

.welcome-body {
  max-width: 480px;
  font-size: 1.05rem;
  color: var(--ash-light);
  line-height: 1.7;
}

.welcome-hint {
  display: flex;
  align-items: center;
  gap: 8px;
  font-family: 'DM Mono', monospace;
  font-size: 0.75rem;
  color: var(--ash);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin-top: 8px;
}

.welcome-hint::before {
  content: '';
  display: inline-block;
  width: 24px;
  height: 1px;
  background: var(--ash);
}

/* ── Responsive ── */
@media (max-width: 720px) {
  .app {
    grid-template-columns: 1fr;
    grid-template-rows: auto auto 1fr;
  }
  .sidebar {
    position: static;
    height: auto;
    display: flex;
    flex-wrap: nowrap;
    overflow-x: auto;
    padding: 0;
    border-right: none;
    border-bottom: 1px solid var(--forge-5);
  }
  .sidebar-section-label, .sidebar-divider { display: none; }
  .tool-btn {
    flex-direction: column;
    gap: 4px;
    padding: 10px 16px;
    border-left: none;
    border-bottom: 2px solid transparent;
    white-space: nowrap;
    min-width: 110px;
    align-items: center;
    text-align: center;
  }
  .tool-btn.active { border-bottom-color: var(--gold); }
  .tool-btn-desc { display: none; }
  .main { padding: 24px 18px; }
  .form-grid { grid-template-columns: 1fr; }
  .result-meta { grid-template-columns: 1fr 1fr; }
}