/*
  Recipe Builder (limiting reactant simulation). Layered on the shared assets/site.css.
  Motion: short transform/opacity transitions only while a reaction runs; nothing loops.
  "Reduce motion" turns every transition off.
*/

.rb {
  --pink: #f472b6;
  --pink-soft: rgba(244, 114, 182, 0.14);
  --tile: 46px;
}

.rb main {
  flex: 1;
  padding-bottom: 32px;
}

.rb-head h1 {
  margin: 4px 0 6px;
  font-family: var(--serif);
  font-size: clamp(1.8rem, 1.3rem + 2vw, 2.6rem);
}

.rb-head .lead {
  margin: 0 0 14px;
  max-width: 60ch;
}

.rb-modes {
  display: inline-flex;
  gap: 4px;
  padding: 4px;
  margin-bottom: 16px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--glass);
}

.rb-modes a {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  padding: 8px 20px;
  border-radius: 999px;
  color: var(--muted);
  font-weight: 700;
  text-decoration: none;
}

.rb-modes a:hover {
  color: var(--text);
}

.rb-modes a[aria-current="page"] {
  background: var(--pink);
  color: var(--on-accent);
}

.rb-label {
  margin: 0 0 10px;
  font-size: 0.8125rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted);
}

.rb-dim {
  color: var(--muted);
  font-weight: 400;
  letter-spacing: 0;
  text-transform: none;
}

.rb-note {
  margin: 8px 0 0;
  font-size: 0.9375rem;
  color: var(--muted);
}

.rb-panel {
  margin: 0 0 14px;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--glass);
}

/* ---------- Reaction picker ---------- */

.rb-picker {
  margin-bottom: 14px;
}

.rb-chips {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 8px;
}

.rb-chip {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 2px;
  min-height: 56px;
  padding: 10px 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--glass);
  color: var(--text);
  font: inherit;
  text-align: left;
  cursor: pointer;
}

.rb-chip:hover {
  border-color: var(--line-strong);
  background: var(--glass-strong);
}

.rb-chip[aria-pressed="true"] {
  border-color: var(--pink);
  background: var(--pink-soft);
}

.rb-chip-name {
  font-weight: 700;
}

.rb-chip-eq {
  font-size: 0.875rem;
  color: var(--muted);
}

.rb-chip[aria-pressed="true"] .rb-chip-eq {
  color: var(--text);
}

/* ---------- Recipe card ---------- */

.rb-recipe-line {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px 10px;
  margin: 0;
}

.rb-recipe-item {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 4px 10px 4px 8px;
  border-radius: 999px;
  background: var(--glass-strong);
}

.rb-coef {
  font-weight: 800;
  font-size: 1.125rem;
}

.rb-formula {
  font-weight: 700;
}

.rb-plus {
  font-size: 1.25rem;
  color: var(--muted);
}

.rb-yields {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--pink);
}

.rb-eq {
  margin: 10px 0 0;
  color: var(--muted);
}

.rb-eq strong {
  color: var(--text);
}

/* ---------- Reactor ---------- */

.rb-reactor {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 12px;
  align-items: start;
}

.rb-arrow {
  align-self: center;
  font-size: 2.25rem;
  font-weight: 800;
  color: var(--pink);
}

.rb-tray {
  grid-column: 1 / -1;
  min-height: 1.6em;
  margin: 0;
  text-align: center;
  font-weight: 700;
  color: var(--amber);
}

.rb-bins {
  display: grid;
  gap: 10px;
}

.rb-bin {
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: rgba(0, 0, 0, 0.22);
}

.rb-bin-head {
  display: flex;
  justify-content: space-between;
  gap: 8px;
  margin-bottom: 6px;
  font-weight: 700;
}

.rb-bin-count {
  color: var(--muted);
  font-weight: 400;
  font-size: 0.9375rem;
}

.rb-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  min-height: var(--tile);
}

.mol {
  display: inline-flex;
  width: var(--tile);
  height: var(--tile);
  padding: 3px;
  border: 2px solid transparent;
  border-radius: 10px;
  transition: transform 0.25s ease, opacity 0.25s ease, border-color 0.2s ease;
}

.mol svg {
  width: 100%;
  height: 100%;
}

.mol .bond {
  stroke: #cbd5e1;
  stroke-width: 3;
  stroke-linecap: round;
}

.mol .atom {
  stroke: rgba(0, 0, 0, 0.35);
  stroke-width: 1;
}

/* in the set that is reacting now */
.mol.is-picked {
  border-color: var(--amber);
  background: var(--amber-soft);
  transform: scale(1.08);
}

/* used up by a completed set: an empty dashed slot */
.mol.is-used {
  border: 2px dashed var(--line-strong);
  background: none;
  transform: none;
}

.mol.is-used svg {
  opacity: 0;
}

.mol.is-born {
  animation: rb-pop 0.3s ease-out;
}

@keyframes rb-pop {
  from { transform: scale(0.3); opacity: 0; }
  to { transform: scale(1); opacity: 1; }
}

.rb-badge {
  margin: 8px 0 0;
  font-size: 0.9375rem;
}

.rb-badge:empty {
  display: none;
}

.rb-bin.is-limiting {
  border-color: var(--bad);
  background: var(--bad-soft);
}

.rb-bin.is-limiting .rb-badge strong {
  color: var(--bad);
}

.rb-bin.is-excess {
  border-color: var(--teal);
}

.rb-bin.is-excess .rb-badge strong {
  color: var(--teal);
}

.rb-bin.is-excess .mol.is-left {
  border-color: var(--teal);
  background: var(--teal-soft);
}

.rb-bin--product {
  border-color: rgba(244, 114, 182, 0.35);
}

/* ---------- Controls ---------- */

.rb-controls {
  margin-bottom: 14px;
}

.rb-stepper {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-bottom: 8px;
}

.rb-step {
  width: 44px;
  min-width: 44px;
  padding: 0;
  font-size: 1.375rem;
}

.rb-step:disabled,
.rb-actions .btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.rb-step-val {
  min-width: 2ch;
  font-weight: 800;
  font-size: 1.125rem;
  text-align: center;
}

.rb-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
}

/* ---------- Sets possible bars ---------- */

.rb-bars {
  display: grid;
  gap: 10px;
}

.rb-bar-row {
  display: grid;
  grid-template-columns: minmax(150px, 14rem) 1fr;
  gap: 10px;
  align-items: center;
}

.rb-bar-track {
  height: 18px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.08);
  overflow: hidden;
}

.rb-bar-fill {
  display: block;
  height: 100%;
  border-radius: 999px;
  background: var(--teal);
  transform-origin: left center;
  transition: transform 0.4s ease;
}

.rb-bar-fill.is-limiting {
  background: var(--bad);
}

/* ---------- Results and Predict ---------- */

.rb-result p {
  margin: 0 0 8px;
}

.rb-result p:last-child {
  margin-bottom: 0;
}

.rb-done {
  padding: 10px 12px;
  border-radius: var(--radius-sm);
  background: var(--good-soft);
}

.rb-done a,
.rb-result a {
  color: var(--text);
}

.rb-good { color: var(--good); }
.rb-half { color: var(--amber); }
.rb-bad { color: var(--bad); }

.rb-predict {
  border-color: rgba(244, 114, 182, 0.4);
}

.rb-round-top {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 10px;
}

.rb-round-top h2:focus {
  outline: none;
}

.rb-score {
  margin: 0;
  font-weight: 700;
}

.rb-prompt {
  margin: 0;
  font-size: 1.0625rem;
}

.rb-questions {
  display: grid;
  gap: 14px;
}

.rb-q {
  margin: 0;
  padding: 0;
  border: 0;
}

.rb-q legend,
.rb-q label {
  display: block;
  margin-bottom: 8px;
  font-weight: 700;
}

.rb-choices {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.rb-choice {
  min-height: 44px;
  min-width: 64px;
  padding: 8px 18px;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  background: var(--glass);
  color: var(--text);
  font: inherit;
  font-weight: 700;
  cursor: pointer;
}

.rb-choice[aria-pressed="true"] {
  border-color: var(--pink);
  background: var(--pink-soft);
}

.rb-choice.is-right {
  border-color: var(--good);
  background: var(--good-soft);
}

.rb-choice.is-wrong {
  border-color: var(--bad);
  background: var(--bad-soft);
}

.rb-amount {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
}

.rb-amount input {
  width: 9rem;
  min-height: 44px;
  padding: 8px 12px;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius-sm);
  background: var(--bg-raised);
  color: var(--text);
  font: inherit;
  font-size: 1.125rem;
}

.rb-amount input.is-right { border-color: var(--good); }
.rb-amount input.is-wrong { border-color: var(--bad); }

.rb-unit {
  font-weight: 700;
}

.rb-summary {
  display: flex;
  gap: 16px;
  align-items: center;
  border-color: rgba(244, 114, 182, 0.4);
}

.rb-summary img {
  flex: none;
}

.rb-summary h2 {
  margin: 0 0 6px;
}

.rb-summary h2:focus {
  outline: none;
}

.rb-summary p {
  margin: 0 0 12px;
}

/* ---------- Legend ---------- */

.rb-legend ul {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 16px;
  margin: 0;
  padding: 0;
  list-style: none;
  font-size: 0.9375rem;
  color: var(--muted);
}

.rb-legend li {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.rb-dot {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.4);
}

/* ---------- Small screens ---------- */

@media (max-width: 720px) {
  .rb { --tile: 40px; }

  .rb-reactor {
    grid-template-columns: 1fr;
  }

  .rb-arrow {
    justify-self: center;
    transform: rotate(90deg);
  }

  .rb-bar-row {
    grid-template-columns: 1fr;
    gap: 4px;
  }

  .rb-summary {
    flex-direction: column;
    align-items: flex-start;
  }
}

@media (prefers-reduced-motion: reduce) {
  .mol,
  .rb-bar-fill {
    transition: none;
  }

  .mol.is-born {
    animation: none;
  }
}