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

:root {
  --panel-width: 240px;
  --bg: #0a0a12;
  --panel-bg: #10101e;
  --border: #1e1e3a;
  --accent: #4fc3f7;
  --text: #cdd6f4;
  --muted: #6e7396;
  --danger: #f38ba8;
  --btn-bg: #1e1e3a;
  --btn-hover: #2a2a4a;
}

html, body {
  width: 100%;
  height: 100%;
  background: var(--bg);
  color: var(--text);
  font-family: 'Segoe UI', system-ui, sans-serif;
  font-size: 13px;
  overflow: hidden;
}

#app {
  display: flex;
  width: 100%;
  height: 100%;
}

#canvas {
  flex: 1;
  display: block;
  cursor: crosshair;
  min-width: 0; /* allow canvas to shrink below its default 300px intrinsic size */
}

#panel {
  width: var(--panel-width);
  min-width: var(--panel-width);
  flex-shrink: 0;
  background: #14142a; /* slightly lighter so it's distinct from the canvas */
  border-left: 3px solid #3a3a6a; /* wider, brighter border so the panel is obvious */
  padding: 16px 12px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  overflow-y: auto;
}

h2 {
  font-size: 15px;
  font-weight: 600;
  color: var(--accent);
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

h3 {
  font-size: 12px;
  font-weight: 600;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 8px;
}

.control-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.control-group label {
  display: flex;
  justify-content: space-between;
  color: var(--text);
}

input[type="range"] {
  width: 100%;
  accent-color: var(--accent);
  cursor: pointer;
}

input[type="color"] {
  width: 100%;
  height: 32px;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: none;
  cursor: pointer;
  padding: 2px;
}

.button-row {
  display: flex;
  gap: 8px;
}

button {
  flex: 1;
  padding: 7px 0;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: var(--btn-bg);
  color: var(--text);
  font-size: 12px;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s;
}

button:hover {
  background: var(--btn-hover);
}

button.active {
  border-color: var(--accent);
  color: var(--accent);
}

/* Mode toggle — segmented control */
.mode-toggle {
  display: flex;
  border: 1px solid var(--border);
  border-radius: 6px;
  overflow: hidden;
  gap: 0;
}

.mode-btn {
  flex: 1;
  border: none;
  border-radius: 0;
  background: var(--btn-bg);
  color: var(--muted);
  font-size: 12px;
  font-weight: 500;
}

.mode-btn + .mode-btn {
  border-left: 1px solid var(--border);
}

.mode-btn:hover {
  background: var(--btn-hover);
  color: var(--text);
}

.mode-btn.active {
  background: var(--accent);
  color: #0a0a12;
  font-weight: 700;
}

.mode-btn.active:hover {
  background: var(--accent);
}

.section-label {
  font-size: 10px;
  font-weight: 700;
  color: #9096c0; /* brighter than --muted so it's legible */
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: -8px;
}

/* Sub-section (e.g. star controls) */
.sub-section {
  display: flex;
  flex-direction: column;
  gap: 8px;
  border-top: 1px solid var(--border);
  padding-top: 12px;
  margin-top: -4px;
}

.sub-section .section-label {
  margin-bottom: 0;
}

.sub-section.hidden {
  display: none;
}

/* Body preview + size controls */
.size-row {
  display: flex;
  gap: 10px;
  align-items: flex-start;
}

#body-preview {
  flex-shrink: 0;
  border-radius: 8px;
  background: #07070f;
  border: 1px solid var(--border);
}

.size-controls {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 8px;
  min-width: 0;
}

.mass-readout {
  font-size: 10px;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
  margin-top: -4px;
}

.body-list-section {
  flex: 1;
  min-height: 0;
  display: flex;
  flex-direction: column;
}

#body-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 6px;
  overflow-y: auto;
  flex: 1;
}

.body-item {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 6px 8px;
  background: #15152a;
  border: 1px solid var(--border);
  border-radius: 4px;
}

.body-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  flex-shrink: 0;
}

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

.body-name {
  font-size: 11px;
  font-weight: 600;
  color: var(--text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.body-vel {
  font-size: 10px;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}

.body-remove {
  flex-shrink: 0;
  padding: 2px 6px;
  font-size: 11px;
  border-radius: 3px;
  background: transparent;
  border: 1px solid transparent;
  color: var(--muted);
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s;
}

.body-remove:hover {
  color: var(--danger);
  border-color: var(--danger);
  background: transparent;
}

.preset-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 5px;
}

.preset-btn {
  font-size: 11px;
  padding: 5px 2px;
}

.hint {
  color: var(--muted);
  font-size: 11px;
  line-height: 1.6;
  border-top: 1px solid var(--border);
  padding-top: 12px;
}

.hint p + p {
  margin-top: 4px;
}