:root {
  --navy: #2c3e50;
  --teal: #1abc9c;
  --gold: #f1c40f;
  --coral: #e74c3c;
  --slate: #556366;
  --softgray: #ecf0f1;
  --white: #ffffff;
  --gray-100: #f7fafc;
  --gray-200: #edf2f7;
  --gray-300: #e2e8f0;
  --max-width: 1120px;
  --radius: 10px;
  --shadow-sm: 0 6px 18px rgba(0, 0, 0, 0.06);
  --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.06);
}

* {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
}

body {
  margin: 0;
  font-family: 'Montserrat', system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial;
  color: var(--navy);
  background: linear-gradient(135deg, #ecf0f1 0%, #d6dbdf 100%);
  padding: 16px;
  font-size: 17px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  line-height: 1.6;
}

.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 16px;
}

/* Header */
.page-header {
  text-align: center;
  padding: 1rem 0;
}

.header-grid {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 12px;
}

.page-title {
  margin: 0;
  font-size: clamp(24px, 2.6vw, 34px);
  font-weight: 700;
}

.header-actions {
  justify-self: end;
}

.subtitle {
  color: var(--slate);
  font-size: 16px;
}

@media (max-width: 767px) {
  .header-grid {
    grid-template-columns: 1fr;
    text-align: left;
  }

  .header-actions {
    justify-self: start;
  }
}

/* Simulation row: canvas + controls side by side on wide screens */
.sim-row {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
  margin-bottom: 16px;
  align-items: stretch;
}

@media (min-width: 980px) {
  .sim-row {
    grid-template-columns: minmax(0, 1.5fr) minmax(420px, 1fr);
  }
}

.sim-stage {
  background: var(--gray-100);
  border-radius: var(--radius);
  padding: 12px;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
}

.scene {
  width: 100%;
  height: auto;
  display: block;
  background: var(--white);
  border-radius: 8px;
  flex: 1;
}

.scene .label-small {
  font-family: 'Inter', sans-serif;
  font-size: 16px;
  fill: var(--slate);
}

.readouts {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 10px;
  margin-top: 12px;
}

@media (min-width: 640px) {
  .readouts {
    grid-template-columns: repeat(4, 1fr);
  }
}

.readout {
  background: var(--white);
  border-radius: 8px;
  padding: 12px 14px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  box-shadow: var(--shadow-xs);
}

.readout-label {
  font-size: 14px;
  color: var(--slate);
}

.readout-value {
  font-size: 22px;
  font-weight: 700;
  color: var(--navy);
  font-variant-numeric: tabular-nums;
}

.readout-value.teal {
  color: var(--teal);
}

/* Controls */
.controls {
  background: var(--white);
  border-radius: var(--radius);
  padding: 18px;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.control-group h3 {
  margin: 0 0 12px;
  font-size: 18px;
  font-weight: 700;
}

.label {
  display: block;
  margin-bottom: 8px;
  font-size: 16px;
  color: var(--slate);
  font-weight: 600;
}

.value {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 6px;
  background: rgba(26, 188, 156, 0.12);
  color: var(--teal);
  font-weight: 700;
  font-size: 16px;
  font-variant-numeric: tabular-nums;
}

.range {
  width: 100%;
}

.hint,
.micro {
  font-size: 14px;
  color: var(--slate);
  margin: 10px 0 0;
  line-height: 1.5;
}

/* Mode switch */
.mode-switch {
  display: grid;
  grid-template-columns: 1fr 1fr;
  border-radius: 8px;
  overflow: hidden;
  border: 1px solid var(--gray-300);
}

.mode-btn {
  background: var(--white);
  border: 0;
  padding: 12px 10px;
  font-family: inherit;
  font-weight: 600;
  font-size: 15px;
  color: var(--slate);
  cursor: pointer;
  transition: all 0.2s ease;
}

.mode-btn.active {
  background: var(--navy);
  color: var(--white);
}

/* Mass transfer */
.mass-row {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 10px;
  align-items: center;
  margin-top: 8px;
}

.mass-stack {
  background: var(--gray-100);
  border-radius: 8px;
  padding: 8px;
  text-align: center;
}

.mass-stack-label {
  font-size: 13px;
  color: var(--slate);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 6px;
}

.mass-stack-vis {
  display: flex;
  flex-direction: column-reverse;
  align-items: center;
  gap: 2px;
  min-height: 60px;
  justify-content: flex-start;
}

.mass-stack-vis .pellet {
  width: 38px;
  height: 8px;
  background: var(--navy);
  border-radius: 2px;
}

.mass-stack-vis.hanger .pellet {
  background: var(--coral);
}

.mass-stack-count {
  font-size: 14px;
  color: var(--navy);
  font-weight: 600;
  margin-top: 6px;
  font-variant-numeric: tabular-nums;
}

.mass-transfer {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.mass-transfer .btn {
  padding: 6px 10px;
  min-width: 44px;
  font-size: 14px;
}

/* Buttons */
.button-stack {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.btn {
  display: inline-block;
  padding: 12px 18px;
  border-radius: 8px;
  font-weight: 600;
  font-size: 16px;
  font-family: inherit;
  text-align: center;
  cursor: pointer;
  border: 1px solid transparent;
  transition: all 0.2s ease;
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn.small {
  padding: 8px 12px;
  font-size: 14px;
}

.teal-btn {
  background: var(--teal);
  color: var(--white);
}

.teal-btn:hover:not(:disabled) {
  background: #17a589;
  transform: translateY(-1px);
}

.gold-btn {
  background: var(--gold);
  color: var(--navy);
}

.gold-btn:hover:not(:disabled) {
  background: #e5b80a;
  transform: translateY(-1px);
}

.coral-btn {
  background: var(--coral);
  color: var(--white);
}

.coral-btn:hover:not(:disabled) {
  background: #d9382b;
  transform: translateY(-1px);
}

.navy-btn {
  background: var(--navy);
  color: var(--white);
}

.navy-btn:hover:not(:disabled) {
  background: #1f2d3a;
  transform: translateY(-1px);
}

/* Panels */
.panel {
  background: var(--white);
  border-radius: var(--radius);
  padding: 16px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 16px;
}

.panel h3 {
  margin: 0 0 14px;
  font-size: 19px;
}

.panel ol {
  margin: 0;
  padding-left: 22px;
  font-size: 16px;
}

.panel ol li {
  margin-bottom: 8px;
  line-height: 1.6;
}

/* Results table */
.table-wrap {
  overflow-x: auto;
}

.results-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 15px;
  font-variant-numeric: tabular-nums;
}

.results-table th,
.results-table td {
  padding: 10px 12px;
  text-align: right;
  border-bottom: 1px solid var(--gray-200);
}

.results-table th:first-child,
.results-table td:first-child {
  text-align: left;
}

.results-table thead th {
  background: var(--gray-100);
  font-weight: 700;
  color: var(--navy);
  border-bottom: 2px solid var(--gray-300);
}

.results-table tbody tr:hover {
  background: var(--gray-100);
}

.results-table .empty-row td {
  text-align: center;
  color: var(--slate);
  padding: 16px;
  font-style: italic;
}

.row-delete {
  background: transparent;
  border: 0;
  color: var(--coral);
  cursor: pointer;
  font-size: 16px;
  padding: 4px 8px;
  border-radius: 4px;
}

.row-delete:hover {
  background: rgba(231, 76, 60, 0.08);
}

.panel-footer {
  margin-top: 12px;
  display: flex;
  justify-content: flex-end;
}

.cell-input {
  width: 90px;
  padding: 8px 10px;
  border: 1px solid var(--gray-300);
  border-radius: 6px;
  font: inherit;
  font-size: 15px;
  text-align: right;
  font-variant-numeric: tabular-nums;
  background: var(--white);
  color: var(--navy);
}

.cell-input:focus {
  outline: none;
  border-color: var(--teal);
  box-shadow: 0 0 0 3px rgba(26, 188, 156, 0.15);
}

.cell-input::-webkit-outer-spin-button,
.cell-input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.cell-input[type='number'] {
  appearance: textfield;
  -moz-appearance: textfield;
}

/* Range input */
input[type='range'] {
  -webkit-appearance: none;
  appearance: none;
  height: 6px;
  background: transparent;
  width: 100%;
}

input[type='range']::-webkit-slider-runnable-track {
  height: 6px;
  background: linear-gradient(90deg, #d0d0d0, #bdbdbd);
  border-radius: 6px;
}

input[type='range']::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--navy);
  margin-top: -8px;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.2);
}

input[type='range']::-moz-range-track {
  height: 6px;
  background: linear-gradient(90deg, #d0d0d0, #bdbdbd);
  border-radius: 6px;
}

input[type='range']::-moz-range-thumb {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--navy);
  border: 0;
}

a:focus,
button:focus,
input:focus {
  outline: 3px solid rgba(26, 188, 156, 0.18);
  outline-offset: 2px;
}

/* Footer */
.site-footer {
  background: var(--navy);
  color: #fff;
  text-align: center;
  padding: 16px;
  font-size: 0.8rem;
  margin: 32px -16px -16px;
}

.site-footer p {
  margin: 0;
}