:root {
  color-scheme: dark;
  --bg: #07111f;
  --panel: rgba(9, 18, 34, 0.88);
  --panel-border: rgba(160, 188, 255, 0.14);
  --text: #f5f7ff;
  --muted: #9eb0d0;
  --accent: #72d6ff;
  --accent-strong: #8a7dff;
  --success: #7fffb1;
  --warning: #ffd46f;
  --danger: #ff8f8f;
  --shadow: 0 24px 60px rgba(0, 0, 0, 0.35);
  --panel-width: 340px;
  --toggle-size: 36px;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
  background:
    radial-gradient(circle at top, rgba(84, 137, 255, 0.16), transparent 32%),
    linear-gradient(180deg, #08111f 0%, #040913 100%);
  color: var(--text);
  font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

body {
  min-height: 100vh;
  overflow: hidden;
}

/* ───────── Layout ───────── */

#app {
  display: grid;
  grid-template-columns: var(--panel-width) 1fr var(--panel-width);
  grid-template-areas: "left viewport right";
  height: 100vh;
  overflow: hidden;
  transition: grid-template-columns 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

#app.left-collapsed {
  grid-template-columns: 0px 1fr var(--panel-width);
}

#app.right-collapsed {
  grid-template-columns: var(--panel-width) 1fr 0px;
}

#app.left-collapsed.right-collapsed {
  grid-template-columns: 0px 1fr 0px;
}

/* ───────── Panels (shared) ───────── */

.control-panel,
.reference-panel {
  position: relative;
  z-index: 2;
  background: var(--panel);
  backdrop-filter: blur(18px);
  box-shadow: var(--shadow);
  overflow: hidden;
  transition: opacity 0.3s ease;
}

.control-panel {
  grid-area: left;
  border-right: 1px solid var(--panel-border);
}

.reference-panel {
  grid-area: right;
  border-left: 1px solid var(--panel-border);
}

.left-collapsed .control-panel,
.right-collapsed .reference-panel {
  opacity: 0;
  pointer-events: none;
}

.panel-scroll {
  height: 100vh;
  overflow-y: auto;
  overflow-x: hidden;
  padding: 24px;
  scrollbar-width: thin;
  scrollbar-color: rgba(114, 214, 255, 0.18) transparent;
}

.panel-scroll::-webkit-scrollbar {
  width: 6px;
}

.panel-scroll::-webkit-scrollbar-track {
  background: transparent;
}

.panel-scroll::-webkit-scrollbar-thumb {
  background: rgba(114, 214, 255, 0.18);
  border-radius: 3px;
}

/* ───────── Toggle buttons ───────── */

.panel-toggle {
  position: fixed;
  z-index: 10;
  top: 50%;
  transform: translateY(-50%);
  width: var(--toggle-size);
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--panel-border);
  background: var(--panel);
  backdrop-filter: blur(14px);
  color: var(--muted);
  cursor: pointer;
  transition: background 0.2s ease, color 0.2s ease, left 0.35s cubic-bezier(0.4, 0, 0.2, 1), right 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

.panel-toggle:hover {
  background: rgba(114, 214, 255, 0.12);
  color: var(--accent);
}

.panel-toggle--left {
  left: var(--panel-width);
  border-radius: 0 10px 10px 0;
  border-left: none;
}

.panel-toggle--left svg {
  transform: rotate(180deg);
  transition: transform 0.3s ease;
}

.left-collapsed .panel-toggle--left {
  left: 0;
}

.left-collapsed .panel-toggle--left svg {
  transform: rotate(0deg);
}

.panel-toggle--right {
  right: var(--panel-width);
  border-radius: 10px 0 0 10px;
  border-right: none;
}

.panel-toggle--right svg {
  transform: rotate(180deg);
  transition: transform 0.3s ease;
}

.right-collapsed .panel-toggle--right {
  right: 0;
}

.right-collapsed .panel-toggle--right svg {
  transform: rotate(0deg);
}

/* ───────── Panel content ───────── */

.panel-header h1,
.control-group h2 {
  margin: 0;
}

.panel-header h1 {
  font-size: 1.15rem;
}

.panel-header p {
  margin: 10px 0 0;
  color: var(--muted);
  line-height: 1.5;
  font-size: 0.9rem;
}

.control-group {
  margin-top: 20px;
  padding: 16px;
  border: 1px solid var(--panel-border);
  border-radius: 16px;
  background: rgba(17, 28, 48, 0.7);
}

.control-group h2 {
  margin-bottom: 12px;
  font-size: 0.92rem;
}

label {
  display: block;
  margin-top: 10px;
  color: var(--muted);
  font-size: 0.9rem;
}

label > span:first-child {
  display: block;
}

select,
input[type="range"] {
  width: 100%;
  margin-top: 6px;
}

input[type="checkbox"] {
  accent-color: var(--accent);
}

select {
  padding: 9px 11px;
  border: 1px solid rgba(140, 167, 235, 0.18);
  border-radius: 10px;
  background: rgba(5, 11, 22, 0.95);
  color: var(--text);
  font-size: 0.88rem;
}

input[type="range"] {
  accent-color: var(--accent);
}

.range-labels,
.info-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.range-labels {
  margin-top: 8px;
  color: var(--muted);
  font-size: 0.82rem;
}

.checkbox-row {
  display: flex;
  align-items: center;
  gap: 10px;
}

.checkbox-row span {
  color: var(--text);
}

.view-toggle {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 8px;
}

.button-row {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 8px;
  margin-top: 12px;
}

.compact-row {
  margin-top: 10px;
}

.mode-button,
.reset-button {
  border: 1px solid rgba(140, 167, 235, 0.2);
  border-radius: 10px;
  background: rgba(10, 18, 33, 0.92);
  color: var(--text);
  cursor: pointer;
  font-size: 0.88rem;
  transition: transform 150ms ease, border-color 150ms ease, background 150ms ease;
}

.mode-button {
  padding: 10px 8px;
}

.mode-button:hover,
.reset-button:hover {
  transform: translateY(-1px);
  border-color: rgba(114, 214, 255, 0.55);
}

.mode-button.is-active {
  background: linear-gradient(135deg, rgba(114, 214, 255, 0.22), rgba(138, 125, 255, 0.22));
  border-color: rgba(114, 214, 255, 0.65);
}

.info-group {
  display: grid;
  gap: 10px;
}

.info-row {
  gap: 10px;
  font-size: 0.9rem;
}

.bond-badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 110px;
  padding: 5px 10px;
  border-radius: 999px;
  font-size: 0.85rem;
  text-transform: lowercase;
}

.bond-badge.none {
  background: rgba(158, 176, 208, 0.14);
  color: var(--muted);
}

.bond-badge.covalent {
  background: rgba(127, 255, 177, 0.14);
  color: var(--success);
}

.bond-badge.polar_covalent {
  background: rgba(255, 212, 111, 0.14);
  color: var(--warning);
}

.bond-badge.ionic {
  background: rgba(255, 143, 143, 0.14);
  color: var(--danger);
}

.bond-badge.metallic {
  background: rgba(114, 214, 255, 0.16);
  color: var(--accent);
}

.bond-badge.semiconductor {
  background: rgba(182, 140, 255, 0.16);
  color: #c6a8ff;
}

.bond-description {
  margin: 4px 0 0;
  color: var(--muted);
  line-height: 1.45;
  font-size: 0.88rem;
}

.legend-group ul {
  margin: 0;
  padding-left: 16px;
  color: var(--muted);
  line-height: 1.5;
  font-size: 0.88rem;
}

.panel-footer {
  margin-top: 20px;
  padding-bottom: 24px;
}

.reset-button {
  width: 100%;
  padding: 10px 14px;
}

/* ───────── Reference panel specifics ───────── */

.ref-section {
  padding: 14px;
}

.formula-card {
  margin-top: 8px;
}

.formula-expr {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--accent);
  padding: 10px 12px;
  background: rgba(114, 214, 255, 0.06);
  border: 1px solid rgba(114, 214, 255, 0.12);
  border-radius: 10px;
  text-align: center;
  line-height: 1.6;
}

.formula-detail {
  display: flex;
  flex-direction: column;
  gap: 4px;
  margin-top: 10px;
  padding: 0 4px;
  color: var(--muted);
  font-size: 0.84rem;
  line-height: 1.5;
}

.ref-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 10px;
  font-size: 0.84rem;
}

.ref-table th,
.ref-table td {
  padding: 7px 8px;
  text-align: left;
  border-bottom: 1px solid rgba(160, 188, 255, 0.08);
}

.ref-table th {
  color: var(--muted);
  font-weight: 500;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.ref-table td {
  color: var(--text);
}

.ref-table--compact td,
.ref-table--compact th {
  padding: 5px 6px;
}

.ref-covalent { color: var(--success); font-weight: 600; }
.ref-polar { color: var(--warning); font-weight: 600; }
.ref-ionic { color: var(--danger); font-weight: 600; }

/* ───────── Viewport ───────── */

.viewport-shell {
  grid-area: viewport;
  position: relative;
  min-width: 0;
  overflow: hidden;
}

.scene-container {
  width: 100%;
  height: 100vh;
}

.scene-container canvas {
  display: block;
}

.scene-error {
  display: grid;
  place-items: center;
  width: 100%;
  height: 100%;
  padding: 24px;
  text-align: center;
  color: #ffd2d2;
  background: radial-gradient(circle at center, rgba(255, 143, 143, 0.1), rgba(4, 9, 19, 0.95));
  font-size: 1rem;
  line-height: 1.6;
}

.atom-tooltip {
  position: absolute;
  z-index: 4;
  min-width: 150px;
  max-width: 220px;
  padding: 10px 12px;
  border: 1px solid rgba(140, 167, 235, 0.18);
  border-radius: 14px;
  background: rgba(8, 15, 29, 0.9);
  color: var(--text);
  backdrop-filter: blur(10px);
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.24);
  pointer-events: none;
  transform: translate3d(0, 0, 0);
}

.atom-tooltip.is-hidden {
  display: none;
}

.atom-tooltip strong {
  display: block;
  margin-bottom: 4px;
  color: var(--accent);
}

.atom-tooltip span {
  display: block;
  color: var(--muted);
  font-size: 0.9rem;
  line-height: 1.4;
}

.scene-hint {
  position: absolute;
  right: 24px;
  bottom: 24px;
  padding: 10px 14px;
  border: 1px solid rgba(140, 167, 235, 0.18);
  border-radius: 999px;
  background: rgba(6, 13, 26, 0.75);
  color: var(--muted);
  backdrop-filter: blur(10px);
  font-size: 0.88rem;
}

/* ───────── Mobile: < 860px ───────── */

@media (max-width: 860px) {
  :root {
    --panel-width: 300px;
  }

  #app,
  #app.left-collapsed,
  #app.right-collapsed,
  #app.left-collapsed.right-collapsed {
    grid-template-columns: 1fr;
    grid-template-rows: 1fr;
    grid-template-areas: "viewport";
  }

  .control-panel,
  .reference-panel {
    position: fixed;
    top: 0;
    height: 100vh;
    width: var(--panel-width);
    transition: transform 0.35s cubic-bezier(0.4, 0, 0.2, 1), opacity 0.3s ease;
  }

  .control-panel {
    left: 0;
    border-right: 1px solid var(--panel-border);
    border-bottom: none;
    transform: translateX(0);
  }

  .reference-panel {
    right: 0;
    border-left: 1px solid var(--panel-border);
    transform: translateX(0);
  }

  #app.left-collapsed .control-panel {
    transform: translateX(calc(-1 * var(--panel-width)));
    opacity: 1;
    pointer-events: auto;
  }

  #app.right-collapsed .reference-panel {
    transform: translateX(var(--panel-width));
    opacity: 1;
    pointer-events: auto;
  }

  #app.left-collapsed .control-panel,
  #app.right-collapsed .reference-panel {
    pointer-events: none;
  }

  .panel-toggle {
    position: fixed;
  }

  .panel-toggle--left {
    left: var(--panel-width);
    transition: left 0.35s cubic-bezier(0.4, 0, 0.2, 1), background 0.2s ease, color 0.2s ease;
  }

  .left-collapsed .panel-toggle--left {
    left: 0;
  }

  .panel-toggle--right {
    right: var(--panel-width);
    transition: right 0.35s cubic-bezier(0.4, 0, 0.2, 1), background 0.2s ease, color 0.2s ease;
  }

  .right-collapsed .panel-toggle--right {
    right: 0;
  }

  .scene-container {
    height: 100vh;
  }

  .scene-hint {
    right: 12px;
    bottom: 12px;
    font-size: 0.8rem;
    padding: 8px 12px;
  }
}

/* ───────── Very small mobile: < 480px ───────── */

@media (max-width: 480px) {
  :root {
    --panel-width: 85vw;
  }

  .panel-scroll {
    padding: 18px 14px;
  }

  .control-group {
    padding: 12px;
  }

  .panel-header h1 {
    font-size: 1.05rem;
  }
}