* { box-sizing: border-box; }
:root {
  --bg: #F1F4F8;
  --panel-bg: #FFFFFF;
  --input-bg: #F7F9FB;
  --border: #DCE2E8;
  --border-strong: #C3CBD4;
  --text: #22222F;
  --text-secondary: #606F7B;
  --text-muted: #8A94A0;
  --accent: #3F7BEF;
  --accent-hover: #2E68D8;
  --danger: #DA2A07;
  --success: #1A7F37;

  /* Canvas drawing colors, read by app.js so the plan matches the page theme */
  --canvas-bg: #FFFFFF;
  --room-stroke: #22222F;
  --clearance-fill: #EDF1F5;
  --row-block-fill: #FFFFFF;
  --row-label: #22222F;
  --brief-header: #22222F;
  --brief-body: #606F7B;
}
:root[data-theme="dark"] {
  --bg: #1B1E24;
  --panel-bg: #22262E;
  --input-bg: #1A1D23;
  --border: #3A4150;
  --border-strong: #4A5262;
  --text: #E6E8EC;
  --text-secondary: #B6BCC6;
  --text-muted: #7C8593;
  --accent: #4F8CFF;
  --accent-hover: #3F7BEF;
  --danger: #FF6B6B;
  --success: #7EE787;

  --canvas-bg: #000000;
  --room-stroke: #EEEEEE;
  --clearance-fill: #1C1F26;
  --row-block-fill: #000000;
  --row-label: #EEEEEE;
  --brief-header: #EEEEEE;
  --brief-body: #AAAAAA;
}
body {
  margin: 0;
  font-family: -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
}
.app {
  display: flex;
  height: 100vh;
}
.panel {
  width: 320px;
  flex-shrink: 0;
  background: var(--panel-bg);
  padding: 20px;
  overflow-y: auto;
  border-right: 1px solid var(--border);
}
.tabs {
  display: flex;
  gap: 0;
  margin-bottom: 20px;
  border-bottom: 1px solid var(--border);
}
.tab-btn {
  flex: 1;
  padding: 10px;
  background: transparent;
  border: none;
  border-bottom: 2px solid transparent;
  color: var(--text-secondary);
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}
.tab-btn:hover {
  color: var(--text);
}
.tab-btn.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}
.tab-content {
  display: none;
}
.tab-content.active {
  display: block;
}
.panel h1 {
  font-size: 18px;
  margin: 0 0 16px;
  color: var(--text);
}
.panel h2 {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
  margin: 18px 0 8px;
}
.field {
  margin-bottom: 10px;
  flex: 1;
}
.field-row {
  display: flex;
  gap: 10px;
}
.field label {
  display: block;
  font-size: 12px;
  color: var(--text-secondary);
  margin-bottom: 4px;
}
.field input, .field select {
  width: 100%;
  padding: 6px 8px;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--input-bg);
  color: var(--text);
  font-size: 13px;
}

/* ---- Spreadsheet-style Ready / Enter / Edit modes for number fields ---- */
.field input[type="number"] {
  caret-color: transparent; /* Ready mode: no visible cursor */
}
.field input[type="number"]:focus {
  outline: none;
}
.field input[type="number"].mode-ready:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 2px rgba(63, 123, 239, 0.25);
}
.field input[type="number"].mode-enter {
  caret-color: var(--accent); /* Enter mode: typing, cursor visible */
  border-color: var(--accent);
  box-shadow: 0 0 0 2px rgba(63, 123, 239, 0.25);
}
.field input[type="number"].mode-edit {
  caret-color: var(--success); /* Edit mode: in-place cursor, distinct color */
  border-color: var(--success);
  box-shadow: 0 0 0 2px rgba(26, 127, 55, 0.2);
}
.field input::placeholder {
  color: var(--text-muted);
}
/* Hide the number input spin arrows */
.field input[type="number"]::-webkit-inner-spin-button,
.field input[type="number"]::-webkit-outer-spin-button {
  -webkit-appearance: none;
  margin: 0;
}
.field input[type="number"] {
  -moz-appearance: textfield;
  appearance: textfield;
}
.hint {
  font-size: 11px;
  color: var(--text-secondary);
  margin: -4px 0 10px;
  line-height: 1.4;
}
.checkbox-field label {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--text);
  cursor: pointer;
}
.checkbox-field input {
  width: auto;
  accent-color: var(--accent);
}
.actions {
  margin-top: 20px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
button {
  padding: 10px;
  border-radius: 6px;
  border: none;
  font-size: 14px;
  cursor: pointer;
  font-weight: 600;
}
#generateBtn {
  background: var(--accent);
  color: #fff;
}
#generateBtn:hover {
  background: var(--accent-hover);
}
#downloadBtn {
  background: var(--input-bg);
  color: var(--text);
  border: 1px solid var(--border);
}
#downloadBtn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}
#downloadBtn:not(:disabled):hover {
  background: var(--border);
}
.message {
  margin-top: 12px;
  font-size: 12px;
  line-height: 1.4;
  white-space: pre-line;
  color: var(--text-secondary);
}
.message.error {
  color: var(--danger);
}
.message.ok {
  color: var(--success);
}
.canvas-wrap {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 20px;
  overflow: auto;
}
canvas {
  background: var(--canvas-bg);
  border: 1px solid var(--border);
  border-radius: 4px;
  max-width: 100%;
  max-height: calc(100vh - 80px);
}
.legend {
  margin-top: 12px;
  display: flex;
  gap: 18px;
  font-size: 12px;
  color: var(--text-secondary);
}
.legend .swatch {
  display: inline-block;
  width: 12px;
  height: 12px;
  border-radius: 2px;
  margin-right: 6px;
  vertical-align: middle;
}
.swatch.rack { background: #4f8cff; }
.swatch.hot { background: #ff6b6b; }
.swatch.cold { background: #6bb8ff; }
.swatch.door { background: #b5651d; }
.swatch.clear { background: var(--clearance-fill); border: 1px solid var(--border); }

.theme-toggle {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 16px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--border);
}
.theme-toggle span {
  font-size: 12px;
  color: var(--text-secondary);
}
.switch {
  position: relative;
  display: inline-block;
  width: 36px;
  height: 20px;
  flex-shrink: 0;
}
.switch input {
  opacity: 0;
  width: 0;
  height: 0;
}
.switch .slider {
  position: absolute;
  inset: 0;
  background: var(--border-strong);
  border-radius: 20px;
  cursor: pointer;
  transition: background 0.2s;
}
.switch .slider::before {
  content: "";
  position: absolute;
  height: 14px;
  width: 14px;
  left: 3px;
  top: 3px;
  background: #fff;
  border-radius: 50%;
  transition: transform 0.2s;
}
.switch input:checked + .slider {
  background: var(--accent);
}
.switch input:checked + .slider::before {
  transform: translateX(16px);
}
.switch input:focus-visible + .slider {
  box-shadow: 0 0 0 2px rgba(63, 123, 239, 0.35);
}
.results-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  margin-top: 16px;
}
.result-item {
  background: var(--input-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 12px;
}
.result-item label {
  display: block;
  font-size: 11px;
  color: var(--text-secondary);
  margin-bottom: 6px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.result-value {
  font-size: 24px;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 4px;
}
.result-formula {
  font-size: 11px;
  color: var(--text-muted);
  font-family: monospace;
  line-height: 1.4;
}
button.full-width {
  width: 100%;
  margin-bottom: 20px;
}