:root {
  --border: #d7d7d7;
  --bg: #f7f7f8;
  --panel-bg: #ffffff;
  --text: #1a1a1a;
  --text-muted: #5a5a5a;
  --accent: #1f6feb;
  --warn-bg: #fff7e6;
  --warn-border: #e0b072;
  --err-bg: #fdecec;
  --err-border: #e08a8a;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  height: 100%;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  color: var(--text);
  background: var(--bg);
}

#root {
  height: 100%;
}

.iq-app {
  display: flex;
  flex-direction: column;
  height: 100vh;
}

/* Header */
.app-header {
  padding: 10px 16px;
  border-bottom: 1px solid var(--border);
  background: var(--panel-bg);
  display: flex;
  align-items: center;
  gap: 12px;
}

.app-header h1 {
  margin: 0;
  font-size: 1.15rem;
}

.lang-toggle {
  margin-left: auto;
  padding: 4px 10px;
  font: inherit;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: inherit;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 6px;
  cursor: pointer;
}
.lang-toggle:hover {
  background: var(--border);
}

/* Body: 3 columns */
.app-body {
  flex: 1;
  display: flex;
  min-height: 0;
}

.panel {
  overflow-y: auto;
  padding: 12px;
}
.panel-left {
  width: 340px;
  border-right: 1px solid var(--border);
  background: var(--panel-bg);
  flex-shrink: 0;
}
.panel-center {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.panel-right {
  width: 340px;
  border-left: 1px solid var(--border);
  background: var(--panel-bg);
  flex-shrink: 0;
}

.panel-title {
  margin: 0 0 8px;
  font-size: 1rem;
}

/* Footer */
.app-footer {
  padding: 6px 16px;
  font-size: 0.78rem;
  color: var(--text-muted);
  border-top: 1px solid var(--border);
  background: var(--panel-bg);
}

/* Controls */
.control-section {
  border: 1px solid var(--border);
  border-radius: 6px;
  margin-bottom: 8px;
  background: #fff;
}
.control-section > summary {
  cursor: pointer;
  padding: 8px 10px;
  font-weight: 600;
  font-size: 0.88rem;
  list-style: revert;
}
.control-body {
  padding: 8px 10px 10px;
  border-top: 1px solid var(--border);
}

.field {
  margin-bottom: 10px;
}
.field-head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
}
.field-label {
  display: block;
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 3px;
}
.field-value {
  font-size: 0.78rem;
  font-variant-numeric: tabular-nums;
  color: var(--text);
}
.input,
.select {
  width: 100%;
  padding: 5px 6px;
  font: inherit;
  font-size: 0.85rem;
  border: 1px solid var(--border);
  border-radius: 5px;
  background: #fff;
}
.slider {
  width: 100%;
}
.subhead {
  margin: 10px 0 4px;
  font-size: 0.8rem;
  font-weight: 600;
}
.slit-row {
  border-top: 1px dashed var(--border);
  padding-top: 6px;
  margin-top: 6px;
}
.checkbox-row {
  display: flex;
  align-items: center;
  gap: 7px;
  font-size: 0.83rem;
  margin: 5px 0;
  cursor: pointer;
}
.caption {
  margin: 4px 0;
  font-size: 0.74rem;
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
}
.warn-inline {
  margin: 4px 0;
  font-size: 0.75rem;
  color: #a06400;
}

.row {
  display: flex;
  gap: 6px;
  align-items: center;
}
.row .select {
  flex: 1;
}

.btn {
  padding: 6px 10px;
  font: inherit;
  font-size: 0.83rem;
  border: 1px solid var(--border);
  border-radius: 5px;
  background: #fff;
  cursor: pointer;
}
.btn:hover {
  background: #f0f0f0;
}
.btn-primary {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.btn-primary:hover {
  background: #1a5fd0;
}

/* Center: summary + warnings + views */
.summary {
  margin: 0;
  padding: 8px 10px;
  background: #0f1720;
  color: #e6edf3;
  border-radius: 6px;
  font-size: 0.76rem;
  line-height: 1.5;
  white-space: pre-wrap;
  overflow-x: auto;
  font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
}
.warnings:empty {
  display: none;
}
.warn,
.error {
  margin: 4px 0;
  padding: 6px 9px;
  border-radius: 5px;
  font-size: 0.8rem;
}
.warn {
  background: var(--warn-bg);
  border: 1px solid var(--warn-border);
}
.error {
  background: var(--err-bg);
  border: 1px solid var(--err-border);
}

.view-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
}
.view-button {
  padding: 5px 10px;
  font: inherit;
  font-size: 0.8rem;
  border: 1px solid var(--border);
  border-radius: 5px;
  background: #fff;
  cursor: pointer;
}
.view-button.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

.plot-area {
  flex: 1;
  min-height: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.plot-panel {
  border: 1px solid var(--border);
  border-radius: 6px;
  background: #fff;
  padding: 8px;
}
.plot-panel-title {
  font-size: 0.82rem;
  font-weight: 600;
  margin-bottom: 6px;
}
.plot-canvas-wrap {
  position: relative;
  height: 260px;
}
.schematic-wrap {
  width: 100%;
}
.schematic-canvas {
  width: 100%;
  display: block;
}
.export-panel .btn {
  display: block;
  width: 100%;
  margin-bottom: 8px;
  text-align: left;
}

/* Explanations */
.explanations .tab-bar {
  display: flex;
  gap: 4px;
  margin: 8px 0;
  flex-wrap: wrap;
}
.tab-button {
  padding: 5px 9px;
  font: inherit;
  font-size: 0.8rem;
  border: 1px solid var(--border);
  border-radius: 5px;
  background: #fff;
  cursor: pointer;
}
.tab-button.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.tab-content .select {
  margin-bottom: 8px;
}
.explain-heading {
  margin: 6px 0;
  font-size: 0.95rem;
}
.explain-text {
  font-size: 0.85rem;
  line-height: 1.5;
  white-space: pre-wrap;
}
.explain-line {
  font-size: 0.85rem;
  line-height: 1.5;
  margin: 6px 0;
}

/* Responsive: stack columns on narrow screens */
@media (max-width: 1000px) {
  .app-body {
    flex-direction: column;
  }
  .panel-left,
  .panel-right {
    width: 100%;
    border: none;
    border-bottom: 1px solid var(--border);
  }
}