.model-calculator {
  --calculator-key-min: 58px;
  display: grid;
  grid-template-columns: minmax(360px, 0.54fr) minmax(0, 1fr);
  gap: 14px;
  align-items: stretch;
}

.model-calculator__entry {
  display: grid;
  gap: 8px;
  align-content: start;
}

.model-calculator__term {
  display: grid;
  align-items: center;
  min-height: 172px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  overflow-x: auto;
  background: var(--surface-strong);
  font-size: 1.08rem;
}

.model-calculator__actions {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 8px;
}

.model-calculator__keys {
  display: grid;
  grid-template-columns: repeat(7, minmax(var(--calculator-key-min), 1fr));
  gap: 8px;
}

.model-calculator__key,
.model-calculator__actions button,
.model-calculator__variable-grid button,
.model-calculator__picker-head button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 52px;
  padding: 0 10px;
  border: 1px solid color-mix(in srgb, var(--line) 65%, transparent);
  border-radius: 8px;
  background: color-mix(in srgb, var(--surface) 84%, var(--bg));
  color: var(--ink);
  font: inherit;
  font-weight: 800;
  cursor: pointer;
}

.model-calculator__key:hover,
.model-calculator__actions button:hover,
.model-calculator__variable-grid button:hover,
.model-calculator__picker-head button:hover {
  border-color: var(--accent);
  color: var(--accent-strong);
}

.mcplaceholder {
  display: inline-block;
  min-width: 1.1em;
  min-height: 0.86em;
  border: 1.5px dotted currentColor;
  border-radius: 3px;
  opacity: 0.72;
}

.mccursor {
  animation: model-calculator-cursor 1s steps(2, start) infinite;
  color: var(--accent-strong);
}

.model-calculator__key:disabled,
.model-calculator__variable-grid button:disabled {
  border-color: color-mix(in srgb, var(--line) 55%, transparent);
  background: color-mix(in srgb, var(--surface) 55%, var(--line));
  color: color-mix(in srgb, var(--muted) 75%, var(--surface));
  cursor: not-allowed;
}

.model-calculator__term.is-error {
  border-color: color-mix(in srgb, var(--coral) 78%, var(--line));
  background: color-mix(in srgb, var(--coral) 12%, var(--surface-strong));
  box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--coral) 35%, transparent);
}

.model-calculator__actions [data-mc-action="add"] {
  border-color: var(--accent);
  background: var(--accent);
  color: #fff;
}

.model-calculator__actions [data-mc-action="backspace"],
.model-calculator__key[data-mc-action="left"],
.model-calculator__key[data-mc-action="right"] {
  background: color-mix(in srgb, var(--line) 34%, var(--surface));
}

.model-calculator__picker {
  position: fixed;
  inset: 0;
  z-index: 260;
  display: grid;
  align-items: start;
  justify-items: center;
  padding: 7vh 20px;
  background: color-mix(in srgb, var(--bg) 72%, transparent);
  backdrop-filter: blur(3px);
}

.model-calculator__picker[hidden] {
  display: none;
}

.model-calculator__picker-panel {
  width: min(900px, 100%);
  max-height: 82vh;
  overflow: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
  box-shadow: 0 24px 80px color-mix(in srgb, #000 20%, transparent);
}

.model-calculator__picker-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 16px;
  border-bottom: 1px solid var(--line);
}

.model-calculator__picker-head h2 {
  margin: 0;
  font-size: 1.08rem;
}

.model-calculator__picker-head button {
  width: 42px;
  min-height: 42px;
}

.model-calculator__variable-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 10px;
  padding: 16px;
}

body.has-model-calculator-picker {
  overflow: hidden;
}

.hero-side-stack {
  display: grid;
  gap: 14px;
}

.regression-case-hero {
  align-items: start;
}

.regression-case-hero .hero-side-stack {
  margin-top: 10px;
}

.regression-reference {
  margin-top: 0.75rem;
  font-size: 0.95rem;
}

.regression-variable-card h2 {
  font-size: 1.05rem;
}

.regression-variable-wrap {
  max-height: 280px;
  overflow: auto;
}

.regression-variable-table th,
.regression-variable-table td {
  vertical-align: top;
  white-space: normal;
}

.regression-variable-table td:first-child {
  width: 120px;
}

.regression-variable-table code {
  color: var(--ink);
  font-weight: 850;
}

.regression-ols-summary {
  display: grid;
  gap: 10px;
  margin-bottom: 12px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface-strong);
}

.regression-ols-head-controls,
.regression-ols-hold-controls {
  display: flex;
  flex-wrap: wrap;
  align-items: end;
  gap: 10px;
}

.regression-ols-head-controls {
  justify-content: flex-end;
}

.regression-ols-hold-controls[hidden] {
  display: none;
}

.regression-ols-hold-controls > span {
  color: var(--muted);
  font-size: 0.8rem;
  font-weight: 850;
  text-transform: uppercase;
}

.regression-ols-hold-controls label {
  display: grid;
  gap: 3px;
  min-width: 74px;
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 850;
}

.regression-ols-hold-controls select {
  min-width: 72px;
}

.regression-ols-equation {
  display: grid;
  gap: 4px;
  overflow-x: auto;
}

.regression-ols-equation span {
  color: var(--muted);
  font-size: 0.8rem;
  font-weight: 850;
  text-transform: uppercase;
}

.regression-ols-equation mjx-container {
  margin: 0 !important;
}

.regression-card-grid {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

@keyframes model-calculator-cursor {
  50% { opacity: 0; }
}

@media (max-width: 1100px) {
  .model-calculator {
    grid-template-columns: 1fr;
  }

  .model-calculator__keys {
    grid-template-columns: repeat(4, minmax(var(--calculator-key-min), 1fr));
  }

  .regression-card-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 620px) {
  .model-calculator__actions,
  .model-calculator__keys {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .regression-card-grid {
    grid-template-columns: 1fr;
  }
}