/* =========================================
   tools.css — Chemistry calculator cards, balancer, molar mass, empirical, solubility
   ========================================= */

/* ========================================
   Chemistry Tools Page - Modular Card Design
   ======================================== */
.chemistry-tools-page {
  align-items: center;
  justify-content: center;
  padding: 0;
  position: relative;
  overflow: hidden;
  /* STRICT NO-SCROLL POLICY */
  height: 100%;
}

/* Background Ambient Orbs Decoration */
.chemistry-tools-page::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 60vh;
  background: radial-gradient(ellipse at top left, rgba(56, 189, 248, 0.12), transparent 70%),
    radial-gradient(ellipse at top right, rgba(167, 139, 250, 0.12), transparent 70%);
  z-index: 0;
  pointer-events: none;
}

html.dark-theme .chemistry-tools-page::before {
  background: radial-gradient(ellipse at top left, rgba(56, 189, 248, 0.05), transparent 70%),
    radial-gradient(ellipse at top right, rgba(167, 139, 250, 0.05), transparent 70%);
}

.chem-tools-container {
  max-width: 1100px;
  width: 100%;
  height: 100%;
  padding: clamp(20px, 4vh, 60px) clamp(20px, 4vw, 60px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
  z-index: 1;
}

.chem-tools-title {
  font-size: clamp(2rem, 5vh, 3.5rem);
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: 0.5vh;
  text-align: center;
  letter-spacing: -0.03em;
}

.chem-tools-subtitle {
  font-size: clamp(0.85rem, 1.8vh, 1.1rem);
  font-weight: 600;
  color: var(--text-secondary);
  text-align: center;
  margin-bottom: clamp(20px, 4vh, 48px);
  letter-spacing: 0.15em;
  text-transform: uppercase;
  opacity: 0.7;
}

.chem-tools-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  grid-template-rows: repeat(2, 1fr);
  gap: clamp(16px, 2.5vh, 32px) clamp(16px, 2.5vw, 32px);
  width: 100%;
  flex: 1;
  max-height: 65vh;
}

@media (max-width: 768px) {
  .chem-tools-grid {
    grid-template-columns: 1fr;
    max-height: none;
  }
}

/* Chemistry Tool Card - Redesigned Premium */
.chem-tool-card {
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  border-radius: clamp(20px, 3vh, 32px);
  padding: clamp(20px, 3.5vh, 40px) clamp(20px, 3vw, 40px);
  cursor: pointer;
  transition: all 0.4s cubic-bezier(0.16, 1, 0.3, 1);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  gap: clamp(12px, 2vh, 24px);
  position: relative;
  overflow: hidden;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.02), inset 0 2px 0 rgba(255, 255, 255, 0.5);
  height: 100%;
}

html.dark-theme .chem-tool-card {
  background: rgba(40, 40, 45, 0.6);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.2), inset 0 2px 0 rgba(255, 255, 255, 0.05);
}

.chem-tool-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  border-radius: clamp(20px, 3vh, 32px);
  background: linear-gradient(135deg, rgba(255, 255, 255, 0.4) 0%, rgba(255, 255, 255, 0.0) 100%);
  z-index: 0;
  pointer-events: none;
  opacity: 0.5;
  transition: opacity 0.4s ease;
}

html.dark-theme .chem-tool-card::before {
  background: linear-gradient(135deg, rgba(255, 255, 255, 0.05) 0%, transparent 100%);
}

.chem-tool-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 16px 32px -8px rgba(0, 0, 0, 0.1), 0 0 0 1px var(--text-highlight);
  background: var(--element-bg);
}

.chem-tool-card:hover::before {
  opacity: 1;
}

.chem-tool-card:active {
  transform: translateY(-2px);
  box-shadow: 0 8px 16px -8px rgba(0, 0, 0, 0.1), 0 0 0 1px var(--text-highlight);
}

.chem-tool-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  position: relative;
  z-index: 1;
  width: 100%;
}

/* Tool Icon Box */
.chem-tool-icon-box {
  width: clamp(54px, 10vh, 72px);
  height: clamp(54px, 10vh, 72px);
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: clamp(16px, 2.5vh, 20px);
  position: relative;
  transition: all 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

.chem-tool-icon-box::after {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: clamp(16px, 2.5vh, 20px);
  box-shadow: inset 0 2px 4px rgba(255, 255, 255, 0.6), inset 0 -2px 4px rgba(0, 0, 0, 0.05);
  pointer-events: none;
}

html.dark-theme .chem-tool-icon-box::after {
  box-shadow: inset 0 2px 4px rgba(255, 255, 255, 0.1), inset 0 -2px 4px rgba(0, 0, 0, 0.2);
}

.chem-tool-icon-box svg {
  width: clamp(28px, 4.5vh, 36px);
  height: clamp(28px, 4.5vh, 36px);
  transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1);
  filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.1));
}

.chem-tool-card:hover .chem-tool-icon-box {
  transform: scale(1.08) rotate(-4deg);
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.1);
}

/* Arrow */
.chem-tool-arrow {
  width: clamp(36px, 6.5vh, 44px);
  height: clamp(36px, 6.5vh, 44px);
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: var(--border-color);
  color: var(--text-primary);
  opacity: 0;
  transform: scale(0.8) translate(-10px, 10px);
  transition: all 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

.chem-tool-arrow svg {
  width: clamp(18px, 3.5vh, 20px);
  height: clamp(18px, 3.5vh, 20px);
  transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

.chem-tool-card:hover .chem-tool-arrow {
  opacity: 1;
  transform: scale(1) translate(0, 0);
  background: var(--text-highlight);
  color: white;
  box-shadow: 0 8px 16px rgba(0, 0, 0, 0.1);
}

.chem-tool-card:hover .chem-tool-arrow svg {
  transform: translateX(2px);
}

/* Tool Number Badge */
.chem-tool-number {
  position: absolute;
  top: clamp(6px, 1.2vh, 8px);
  left: clamp(8px, 1.5vh, 10px);
  font-size: clamp(10px, 1.6vh, 11px);
  font-weight: 800;
  color: inherit;
  opacity: 0.5;
}

/* Tool Info Section */
.chem-tool-info {
  display: flex;
  flex-direction: column;
  gap: clamp(8px, 1.5vh, 12px);
  position: relative;
  z-index: 1;
}

.chem-tool-name {
  font-size: clamp(1.25rem, 2.5vh, 1.6rem);
  font-weight: 800;
  color: var(--text-primary);
  letter-spacing: -0.02em;
  margin: 0;
  transition: color 0.3s ease;
}

.chem-tool-card:hover .chem-tool-name {
  color: var(--text-highlight);
}

.chem-tool-desc {
  font-size: clamp(0.9rem, 1.7vh, 1rem);
  color: var(--text-secondary);
  line-height: 1.6;
  margin: 0;
  font-weight: 500;
  opacity: 0.85;
}

/* Tool Icon Color Variations */
.balancer-icon {
  background: linear-gradient(135deg, #ffcccc 0%, #ffe5cc 100%);
  color: #c2410c;
}

.molar-icon {
  background: linear-gradient(135deg, #fff2cc 0%, #d9e2f3 100%);
  color: #854d0e;
}

.percent-icon {
  background: linear-gradient(135deg, #d1e7dd 0%, #e2f0d9 100%);
  color: #047857;
}

.empirical-icon {
  background: linear-gradient(135deg, #e0ccff 0%, #d9e2f3 100%);
  color: #6d28d9;
}

html.dark-theme .balancer-icon,
html.dark-theme .molar-icon,
html.dark-theme .percent-icon,
html.dark-theme .empirical-icon {
  opacity: 0.9;
}

/* Tool Tags */
.chem-tool-tags {
  display: flex;
  gap: clamp(6px, 1vw, 10px);
  margin-top: clamp(6px, 1vh, 10px);
  align-items: center;
}

.grade-tag,
.feature-tag {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: clamp(22px, 4vh, 26px);
  padding: 0 clamp(8px, 1.5vw, 12px);
  border-radius: clamp(6px, 0.8vh, 8px);
  font-size: clamp(10px, 1.6vh, 12px);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  white-space: nowrap;
}

.grade-tag {
  background: rgba(120, 53, 15, 0.08);
  color: #b45309;
  border: 1px solid rgba(120, 53, 15, 0.15);
}

html.dark-theme .grade-tag {
  color: #fcd34d;
  background: rgba(252, 211, 77, 0.1);
  border-color: rgba(252, 211, 77, 0.2);
}

.feature-tag {
  background: rgba(0, 0, 0, 0.03);
  color: var(--text-secondary);
  border: 1px solid rgba(0, 0, 0, 0.08);
}

html.dark-theme .feature-tag {
  background: rgba(255, 255, 255, 0.05);
  border-color: rgba(255, 255, 255, 0.1);
}

/* Original tool styles (for modal content) */
.tools-title {
  font-size: 3.5vmin;
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: 0.8vmin;
  text-align: center;
  letter-spacing: -0.03em;
}

.tools-subtitle {
  font-size: 1.1vmin;
  font-weight: 600;
  color: var(--text-secondary);
  text-align: center;
  margin-bottom: 4vmin;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  opacity: 0.7;
}

.tool-section {
  background: var(--element-bg);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  padding: 24px;
  margin-bottom: 2vmin;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.04);
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

.tool-section:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.08);
  border-color: rgba(0, 0, 0, 0.1);
}

.tool-heading {
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 20px;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 12px;
  letter-spacing: -0.02em;
}

.tool-input-group {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 20px;
}

.tool-input-group label {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  opacity: 0.8;
}

.tool-input,
.tool-select {
  padding: 14px 18px;
  border: 1px solid var(--border-color);
  border-radius: 12px;
  font-size: 1.05rem;
  font-family: "Inter", sans-serif;
  background: var(--bg-color);
  color: var(--text-primary);
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

.tool-input:focus,
.tool-select:focus {
  outline: none;
  border-color: rgba(0, 0, 0, 0.2);
  background: #ffffff;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
  transform: translateY(-1px);
}

.tool-button {
  padding: 12px 24px;
  background: var(--text-primary);
  color: var(--bg-color);
  border: 1px solid var(--text-primary);
  border-radius: 12px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
  font-family: "Inter", sans-serif;
}

.tool-button:hover {
  background: var(--text-highlight);
  border-color: var(--text-highlight);
  transform: translateY(-2px) scale(1.02);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.12);
}

.tool-button:active {
  transform: translateY(0) scale(1);
}

.tool-result {
  background: var(--element-bg);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 20px;
  margin-top: 20px;
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text-primary);
  font-family: "Inter", sans-serif;
  text-align: center;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
}

.tool-explanation {
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  border-left: 4px solid var(--text-highlight);
  border-radius: 12px;
  padding: 20px;
  margin-top: 16px;
  font-size: 0.95rem;
  line-height: 1.6;
  color: var(--text-primary);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
}

.tool-explanation h4 {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text-highlight);
  letter-spacing: -0.01em;
}

.tool-explanation ol,
.tool-explanation ul {
  margin-left: 20px;
  margin-top: 8px;
}

.tool-explanation li {
  margin-bottom: 6px;
}

.tool-check {
  background: var(--element-bg);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 20px;
  margin-top: 16px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
}

.tool-check h4 {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text-primary);
  letter-spacing: -0.01em;
}

.tool-check table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 8px;
}

.tool-check td {
  padding: 8px;
  border-bottom: 1px solid rgba(0, 0, 0, 0.05);
  font-family: "Courier New", monospace;
}

.tool-check td:first-child {
  font-weight: 600;
}

.tool-breakdown {
  background: var(--element-bg);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 20px;
  margin-top: 16px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
}

.tool-breakdown table {
  width: 100%;
  border-collapse: collapse;
}

.tool-breakdown th {
  text-align: left;
  padding: 12px;
  font-weight: 600;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-secondary);
  border-bottom: 1px solid var(--border-color);
  opacity: 0.8;
}

.tool-breakdown td {
  padding: 12px;
  border-bottom: 1px solid var(--border-color);
  font-family: "Inter", monospace;
  color: var(--text-primary);
}

.tool-breakdown tr:last-child td {
  border-bottom: none;
  font-weight: 700;
  background: var(--bg-color);
  border-top: 1px solid var(--border-color);
}

.formula-inputs-container {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 20px;
}

.element-input-row {
  display: grid;
  grid-template-columns: 120px 1fr 1fr;
  gap: 12px;
  align-items: center;
}

.element-input-row label {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  opacity: 0.8;
}

.element-input-row input {
  padding: 10px 14px;
  border: 1px solid var(--border-color);
  border-radius: 12px;
  font-size: 0.95rem;
  font-family: "Inter", sans-serif;
  background: var(--bg-color);
  color: var(--text-primary);
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

.element-input-row input:focus {
  outline: none;
  border-color: rgba(0, 0, 0, 0.2);
  background: #ffffff;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.06);
}

/* Features Page Styles */
.features-page {
  align-items: flex-start;
  padding-top: 80px;
}

.features-container {
  max-width: 1200px;
  width: 100%;
  padding: 20px;
}

.features-title {
  font-size: 3.5vmin;
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: 0.8vmin;
  text-align: center;
  letter-spacing: -0.03em;
}

.features-subtitle {
  font-size: 1.1vmin;
  font-weight: 600;
  color: var(--text-secondary);
  text-align: center;
  margin-bottom: 4vmin;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  opacity: 0.7;
}

/* Ion elements: responsive to width only.
   Boxes keep a reasonable minimum size; page scrolls vertically if needed. */
.ions-table-page .element {
  width: clamp(60px, 5vw, 90px);
  container-type: inline-size;
}

/* Long formulas (e.g. CH₃COO⁻) need smaller symbol text to fit */
.ions-table-page .element.ion-long-formula .symbol {
  font-size: 22cqi;
}


.feature-modal-body {
  padding: 60px;
  height: 100%;
  overflow: auto;
  display: flex;
  flex-direction: column;
  position: relative;
}

/* Tool name label - plain text in padding area */
.tool-padding-label {
  position: absolute;
  top: 20px;
  left: 60px;
  font-size: 1.25rem;
  font-weight: 700;
  color: #1e293b;
  letter-spacing: -0.02em;
  pointer-events: none;
}

.feature-modal-body::-webkit-scrollbar {
  display: none;
}

/* Feature modal uses same size as element modal */
#feature-modal-content {
  flex-direction: column;
}

.feature-detail-header {
  display: flex;
  align-items: center;
  gap: 24px;
  margin-bottom: 24px;
}

.feature-detail-icon {
  width: 100px;
  height: 100px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--element-bg);
  border-radius: 16px;
  border: 1px solid var(--border-color);
  font-size: 3rem;
  flex-shrink: 0;
}

.feature-detail-title {
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--text-primary);
  letter-spacing: -0.03em;
  margin: 0;
}

.feature-detail-content {
  font-size: 1rem;
  line-height: 1.8;
  color: var(--text-primary);
}

.feature-detail-section {
  background: var(--element-bg);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 24px;
  margin-top: 16px;
}

.feature-detail-section h3 {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 16px;
  letter-spacing: -0.02em;
}

.feature-detail-section p {
  font-size: 0.95rem;
  line-height: 1.7;
  color: var(--text-secondary);
  margin-bottom: 12px;
}

.feature-detail-section ul {
  margin-left: 24px;
  margin-top: 12px;
}

.feature-detail-section li {
  font-size: 0.95rem;
  line-height: 1.7;
  color: var(--text-secondary);
  margin-bottom: 8px;
}

.tool-modal-title-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.tool-modal-content {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

/* Special two-column layout for Empirical Formula tool */
.tool-modal-content.empirical-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  align-items: start;
}

.empirical-left {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.empirical-right {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.empirical-layout .tool-result-box,
.empirical-layout .tool-explanation-box {
  grid-column: span 2;
}

.compact-tips {
  padding: 20px;
}

.compact-tips h4 {
  font-size: 1rem;
  margin-bottom: 10px;
}

.compact-tips ol,
.compact-tips ul {
  margin-left: 20px;
  line-height: 1.6;
}

.compact-tips li {
  margin-bottom: 6px;
  font-size: 0.95rem;
}

/* ========================================
   Balance Scale Balancer UI
   ======================================== */
.balancer-scale-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 24px;
  padding: 20px;
  height: 100%;
  background: linear-gradient(180deg, #ffffff 0%, #f8fafc 100%);
  border-radius: 24px;
  overflow: hidden;
}

/* SVG Balance Scale */
.balance-scale-svg {
  width: 100%;
  max-width: 500px;
  height: auto;
  filter: drop-shadow(0 4px 15px rgba(0, 0, 0, 0.1));
}

.scale-stand,
.scale-base {
  stroke: #94a3b8;
  fill: none;
}

.scale-pivot {
  fill: #475569;
  stroke: #94a3b8;
  stroke-width: 2;
}

.scale-pivot-cap {
  fill: #64748b;
}

.scale-beam-group {
  transform-origin: 250px 95px;
  transition: transform 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.scale-beam {
  stroke: #e2e8f0;
  fill: none;
}

.scale-chain {
  stroke: #94a3b8;
  stroke-width: 2;
  fill: none;
}

.scale-pan {
  fill: none;
  stroke: #e2e8f0;
  stroke-width: 2;
  color: #e2e8f0;
}

.scale-label {
  fill: #475569;
  font-size: 13px;
  font-weight: 600;
  font-family: "Inter", sans-serif;
}

/* Pan and suspension physics - keep pans level via Y translation */
.scale-pan,
.left-suspension,
.right-suspension {
  transition: transform 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);
}

/* Tilting animations - entire scale tilts as one unit */
.scale-beam-group.tilt-left {
  transform: rotate(-12deg);
}

.scale-beam-group.tilt-right {
  transform: rotate(12deg);
}

.scale-beam-group.tilt-left-slight {
  transform: rotate(-6deg);
}

.scale-beam-group.tilt-right-slight {
  transform: rotate(6deg);
}

.scale-beam-group.balanced {
  transform: rotate(0deg);
}

/* Physics wobble animation when transitioning */
@keyframes pan-wobble {
  0% {
    transform: rotate(0deg);
  }

  15% {
    transform: rotate(3deg);
  }

  30% {
    transform: rotate(-2deg);
  }

  45% {
    transform: rotate(1.5deg);
  }

  60% {
    transform: rotate(-1deg);
  }

  75% {
    transform: rotate(0.5deg);
  }

  100% {
    transform: rotate(0deg);
  }
}

.scale-beam-group.wobbling .left-pan,
.scale-beam-group.wobbling .right-pan {
  animation: pan-wobble 0.6s ease-out;
}

/* Shake animation for auto-balance */
@keyframes scale-shake {

  0%,
  100% {
    transform: rotate(0deg);
  }

  10% {
    transform: rotate(-5deg);
  }

  20% {
    transform: rotate(5deg);
  }

  30% {
    transform: rotate(-4deg);
  }

  40% {
    transform: rotate(4deg);
  }

  50% {
    transform: rotate(-3deg);
  }

  60% {
    transform: rotate(3deg);
  }

  70% {
    transform: rotate(-2deg);
  }

  80% {
    transform: rotate(2deg);
  }

  90% {
    transform: rotate(-1deg);
  }
}

.scale-beam-group.shaking {
  animation: scale-shake 0.8s ease-out;
}

/* Input Areas */
.balancer-inputs {
  display: flex;
  align-items: flex-start;
  gap: 16px;
  width: 100%;
  max-width: 600px;
}

.balancer-formula-input {
  padding: 14px 18px;
  border: 2px solid #e2e8f0;
  border-radius: 12px;
  font-size: 1.1rem;
  font-family: "Inter", sans-serif;
  background: white;
  color: #1e293b;
  text-align: center;
  transition: all 0.3s ease;
}

.balancer-formula-input:focus {
  outline: none;
  border-color: #6366f1;
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

.balancer-formula-input::placeholder {
  color: #94a3b8;
}

.balancer-arrow {
  font-size: 2rem;
  color: #94a3b8;
  font-weight: 300;
}

.atom-count-display {
  font-size: 0.8rem;
  color: #64748b;
  text-align: center;
  min-height: 20px;
}

/* Feedback Area */
.balancer-feedback {
  padding: 12px 24px;
  border-radius: 12px;
  background: #f1f5f9;
  border: 1px solid #e2e8f0;
  text-align: center;
  min-height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.feedback-text {
  color: #64748b;
  font-size: 0.95rem;
}

.balancer-feedback.balanced {
  background: rgba(34, 197, 94, 0.1);
  border-color: rgba(34, 197, 94, 0.3);
}

.balancer-feedback.balanced .feedback-text {
  color: #22c55e;
  font-weight: 600;
}

.balancer-feedback.unbalanced {
  background: rgba(251, 191, 36, 0.15);
  border-color: rgba(251, 191, 36, 0.4);
}

.balancer-feedback.unbalanced .feedback-text {
  color: #d97706;
}

/* Auto Balance Button */
.auto-balance-btn {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px 32px;
  background: linear-gradient(135deg, #6366f1 0%, #4f46e5 100%);
  color: white;
  border: none;
  border-radius: 12px;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
  box-shadow: 0 4px 14px rgba(99, 102, 241, 0.35);
}

.auto-balance-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(99, 102, 241, 0.4);
}

.auto-balance-btn:active {
  transform: translateY(0);
}

.auto-balance-btn svg {
  transition: transform 0.3s ease;
}

.auto-balance-btn:hover svg {
  transform: rotate(90deg);
}

/* Balanced Equation Display */
.balanced-equation-display {
  padding: 20px 32px;
  background: rgba(34, 197, 94, 0.1);
  border: 2px solid rgba(34, 197, 94, 0.3);
  border-radius: 16px;
  text-align: center;
}

.balanced-label {
  font-size: 0.85rem;
  font-weight: 600;
  color: #94a3b8;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 8px;
}

.balanced-value {
  font-size: 1.8rem;
  font-weight: 800;
  color: #22c55e;
  letter-spacing: 0.02em;
}

/* End Balance Scale Styles */

.tool-input-section {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.tool-input-section label {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.tool-input-hint {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin: 0;
  font-style: italic;
}

.tool-button.primary-btn {
  padding: 14px 28px;
  background: linear-gradient(135deg, var(--text-primary) 0%, #4a3f36 100%);
  color: var(--bg-color);
  border: none;
  border-radius: 12px;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
  align-self: flex-start;
}

.tool-button.primary-btn:hover {
  transform: translateY(-2px) scale(1.02);
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.15);
}

.tool-result-box {
  background: linear-gradient(135deg, var(--element-bg) 0%, #f9f5ef 100%);
  border: 2px solid var(--border-color);
  border-radius: 16px;
  padding: 28px;
  text-align: center;
}

.big-value {
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--text-highlight);
}

.unit {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-left: 8px;
}

.tool-explanation-box,
.tool-breakdown-box,
.tool-check-box {
  background: var(--element-bg);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 24px;
}

.tool-explanation-box h4,
.tool-breakdown-box h4,
.tool-check-box h4 {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 16px;
}

.tool-explanation-box ol,
.tool-explanation-box ul {
  margin-left: 24px;
  line-height: 1.8;
}

.tool-explanation-box li {
  margin-bottom: 8px;
  color: var(--text-primary);
}

.tool-tips-section h4 {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 12px;
}

.tool-tips-section ul,
.tool-tips-section ol {
  margin-left: 24px;
  line-height: 1.7;
}

.tool-tips-section li {
  color: var(--text-secondary);
  margin-bottom: 8px;
}

.tool-tips-section p {
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 10px;
}


/* Section Icon Styling */
.section-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 20px;
  height: 20px;
  margin-right: 8px;
  vertical-align: middle;
  color: var(--text-highlight);
}

.section-icon svg {
  width: 100%;
  height: 100%;
}

.section-icon.warning {
  color: #dc6b00;
}

/* Tool Modal Icon Theming */
.tool-modal-icon.balancer-icon {
  background: linear-gradient(135deg, #fee2e2 0%, #fecaca 100%);
  color: #b91c1c;
}

.tool-modal-icon.molar-icon {
  background: linear-gradient(135deg, #fef3c7 0%, #fde68a 100%);
  color: #b45309;
}

.tool-modal-icon.percent-icon {
  background: linear-gradient(135deg, #d1fae5 0%, #a7f3d0 100%);
  color: #047857;
}

.tool-modal-icon.empirical-icon {
  background: linear-gradient(135deg, #e0e7ff 0%, #c7d2fe 100%);
  color: #4338ca;
}

/* Enhanced Tool Select */
.tool-select {
  padding: 12px 16px;
  border: 1px solid var(--border-color);
  border-radius: 12px;
  font-size: 1rem;
  font-family: "Inter", sans-serif;
  background: var(--bg-color);
  color: var(--text-primary);
  cursor: pointer;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%235D544F' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10l-5 5z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 16px center;
  padding-right: 40px;
}

.tool-select:focus {
  outline: none;
  border-color: var(--text-highlight);
  box-shadow: 0 0 0 3px rgba(120, 53, 15, 0.1);
}

/* Enhanced Warning Box */
.warning-box {
  background: linear-gradient(135deg, #fef3c7 0%, #fde68a 100%);
  border: 1px solid #f59e0b;
  border-radius: 12px;
  padding: 14px 18px;
  margin-top: 12px;
  font-size: 0.9rem;
  color: #92400e;
  display: flex;
  align-items: center;
  gap: 10px;
}

.warning-box::before {
  content: "";
  display: inline-block;
  width: 20px;
  height: 20px;
  min-width: 20px;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%2392400E' stroke-width='2'%3E%3Cpath d='M10.29 3.86L1.82 18a2 2 0 0 0 1.71 3h16.94a2 2 0 0 0 1.71-3L13.71 3.86a2 2 0 0 0-3.42 0z'/%3E%3Cline x1='12' y1='9' x2='12' y2='13'/%3E%3Cline x1='12' y1='17' x2='12.01' y2='17'/%3E%3C/svg%3E");
  background-size: contain;
  background-repeat: no-repeat;
}

/* h4 in tool sections */
.tool-tips-section h4,
.tool-explanation-box h4,
.tool-breakdown-box h4,
.tool-check-box h4 {
  display: flex;
  align-items: center;
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
}


/* ========================================
   Molar Mass Calculator - Electronic Scale
   倾斜3D电子秤 + 精准出票
   ======================================== */

/* 整体包裹器 - 3D透视空间 */
.electronic-scale-wrapper {
  position: relative;
  width: 360px;
  margin: 0 auto 60px;
  transform-style: preserve-3d;
  transform: rotateX(15deg) rotateZ(-3deg);
  /* 不要transition，保持固定 */
}

/* Ground shadow - 桌面投影 */
.electronic-scale-wrapper::after {
  content: "";
  position: absolute;
  bottom: -40px;
  left: 50%;
  transform: translateX(-50%) rotateZ(3deg);
  width: 85%;
  height: 30px;
  background: radial-gradient(ellipse at center,
      rgba(0, 0, 0, 0.13) 0%,
      transparent 70%);
  border-radius: 50%;
  pointer-events: none;
}

/* 元素方块区域 - 固定高度 */
.scale-blocks-area {
  display: flex;
  align-items: flex-end;
  justify-content: center;
  gap: 10px;
  height: 100px;
  /* 固定高度，不随内容变化 */
  padding: 10px;
  margin-bottom: 0;
  position: relative;
  z-index: 10;
}

/* Individual Element Blocks */
.element-block {
  position: relative;
  border-radius: 12px;
  box-shadow:
    inset 0 0 15px rgba(255, 255, 255, 0.3),
    inset 0 -2px 5px rgba(0, 0, 0, 0.1),
    0 4px 8px rgba(0, 0, 0, 0.15);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  color: white;
  font-size: 1.2rem;
  cursor: pointer;
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
  border: 1px solid rgba(255, 255, 255, 0.4);
  min-width: 45px;
  min-height: 45px;
  text-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  animation: blockBounceIn 0.45s cubic-bezier(0.34, 1.56, 0.64, 1) both;
}

@keyframes blockBounceIn {
  0% {
    opacity: 0;
    transform: translateY(-40px) scale(0.6);
  }

  60% {
    opacity: 1;
    transform: translateY(4px) scale(1.05);
  }

  80% {
    transform: translateY(-2px) scale(0.98);
  }

  100% {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

.element-block:hover {
  transform: scale(1.08) translateY(-8px);
  z-index: 10;
  box-shadow: 0 15px 30px rgba(0, 0, 0, 0.25);
}

/* Tooltip for hover */
.block-tooltip {
  position: absolute;
  bottom: calc(100% + 10px);
  left: 50%;
  transform: translateX(-50%) translateY(5px);
  background: rgba(30, 41, 59, 0.95);
  color: white;
  padding: 8px 12px;
  border-radius: 12px;
  font-size: 0.85rem;
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  transition: all 0.2s cubic-bezier(0.175, 0.885, 0.32, 1.275);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
  z-index: 20;
  font-family: "Inter", sans-serif;
}

.block-tooltip::after {
  content: "";
  position: absolute;
  top: 100%;
  left: 50%;
  margin-left: -6px;
  border-width: 6px;
  border-style: solid;
  border-color: rgba(30, 41, 59, 0.95) transparent transparent transparent;
}

.element-block:hover .block-tooltip {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

/* The Scale itself - 秤主体 */
.electronic-scale-base {
  width: 100%;
  height: 100px;
  background: linear-gradient(180deg, #e2e8f0 0%, #cbd5e1 100%);
  border-radius: 16px;
  box-shadow:
    0 8px 0 #94a3b8,
    0 20px 40px rgba(0, 0, 0, 0.2),
    inset 0 1px 0 rgba(255, 255, 255, 0.8);
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 15px 20px;
  position: relative;
  z-index: 10;
}

.electronic-scale-base::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  border-radius: 16px;
  background: linear-gradient(135deg,
      rgba(255, 255, 255, 0.5) 0%,
      transparent 50%);
  pointer-events: none;
}

/* Metal Platform on top - 顶部称重台 */
.scale-platform-top {
  width: 280px;
  height: 12px;
  border-radius: 100px;
  margin-top: -6px;
  margin-bottom: 10px;
  box-shadow: 0 3px 6px rgba(0, 0, 0, 0.15);
  background: linear-gradient(to right,
      #78909c,
      #b0bec5 30%,
      #78909c 70%,
      #546e7a);
  transition:
    transform 0.35s cubic-bezier(0.25, 0.8, 0.25, 1),
    filter 0.35s ease;
}

.scale-platform-top.has-weight {
  transform: translateY(2px);
  filter: brightness(0.95);
}

/* Digital Screen - 数字显示屏 */
.scale-screen {
  width: 220px;
  height: 50px;
  background: #0a0f1a;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  padding: 0 15px;
  font-family: "Courier New", monospace;
  font-size: 1.8rem;
  color: #4ade80;
  box-shadow: inset 0 3px 10px rgba(0, 0, 0, 0.7);
  border: 2px solid #1e293b;
  letter-spacing: 2px;
}

.receipt-wrapper::before {
  /* 去掉顶部锯齿，避免漏出 */
  display: none;
}

.receipt-wrapper::after {
  /* 锯齿底边 */
  content: "";
  position: absolute;
  bottom: -8px;
  left: 0;
  width: 100%;
  height: 8px;
  background:
    linear-gradient(135deg, #f9fafb 50%, transparent 50%),
    linear-gradient(-135deg, #f9fafb 50%, transparent 50%);
  background-size: 10px 8px;
  background-repeat: repeat-x;
}

.receipt-header {
  text-align: center;
  border-bottom: none;
  padding-bottom: 6px;
  margin-bottom: 0;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 3px;
  font-size: 0.9rem;
  color: #374151;
}

/* 条形码样式 */
.receipt-barcode {
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 1.2rem;
  letter-spacing: -1px;
  color: #1f2937;
  margin: 4px 0 8px;
  border-bottom: 1px dashed #d1d5db;
  padding-bottom: 10px;
  width: 100%;
}

.receipt-date {
  font-size: 0.7rem;
  text-align: center;
  color: #9ca3af;
  margin-top: 0;
  margin-bottom: 12px;
  letter-spacing: 0.5px;
}

.receipt-item-row {
  display: flex;
  justify-content: space-between;
  margin-bottom: 6px;
  font-size: 0.8rem;
  line-height: 1.4;
}

.receipt-item-name {
  display: flex;
  gap: 6px;
  color: #4b5563;
}

.receipt-item-qty {
  color: #9ca3af;
  font-size: 0.75rem;
}

.receipt-total-row {
  border-top: 1px dashed #d1d5db;
  margin-top: 12px;
  padding-top: 10px;
  display: flex;
  justify-content: space-between;
  font-weight: 700;
  font-size: 1rem;
  color: #1f2937;
}

.receipt-footer {
  text-align: center;
  font-size: 0.65rem;
  margin-top: 14px;
  color: #9ca3af;
  text-transform: uppercase;
  letter-spacing: 1px;
  border-top: 1px dashed #e5e7eb;
  padding-top: 10px;
}

/* ========================================
   Molar Mass Scale - Realtime Split Layout
   ======================================== */
.molar-tool-layout {
  display: grid;
  grid-template-columns: 1fr 1.4fr;
  gap: 40px;
  height: 100%;
  align-items: start;
}

/* LEFT COLUMN: Inputs & Tips */
.molar-input-panel {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

/* Glass float card for input section */
.molar-input-panel .tool-input-section {
  padding: 20px;
  background: rgba(255, 255, 255, 0.72);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border-radius: 16px;
  border: 1px solid rgba(255, 255, 255, 0.6);
  box-shadow:
    0 2px 8px rgba(0, 0, 0, 0.04),
    0 8px 24px rgba(0, 0, 0, 0.08),
    inset 0 1px 0 rgba(255, 255, 255, 0.8);
  transition: all 0.2s ease;
}

.molar-input-panel .tool-input-section:hover {
  box-shadow:
    0 4px 12px rgba(0, 0, 0, 0.06),
    0 12px 32px rgba(0, 0, 0, 0.1),
    inset 0 1px 0 rgba(255, 255, 255, 0.9);
}

.molar-input-panel .tool-input-section:focus-within {
  border-color: rgba(99, 102, 241, 0.4);
  box-shadow:
    0 0 0 3px rgba(99, 102, 241, 0.12),
    0 4px 12px rgba(0, 0, 0, 0.06),
    0 12px 32px rgba(0, 0, 0, 0.1),
    inset 0 1px 0 rgba(255, 255, 255, 0.9);
}

/* Input card label with icon */
.molar-input-label {
  display: flex !important;
  align-items: center;
  gap: 8px;
  font-size: 0.8rem !important;
  font-weight: 600 !important;
  color: #475569 !important;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.molar-label-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  background: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);
  border-radius: 7px;
  color: #fff;
  flex-shrink: 0;
}

/* Options row */
.molar-options-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 12px;
  flex-wrap: wrap;
  gap: 12px;
}

.molar-exact-label {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.85rem;
  color: #475569;
  cursor: pointer;
  font-weight: 500;
}

.molar-exact-label input[type="checkbox"] {
  width: 16px;
  height: 16px;
  accent-color: #6366f1;
}

/* RIGHT COLUMN: The Stage */
.molar-scale-stage {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start;
  padding-top: 0;
  padding-bottom: 200px;
  position: relative;
  perspective: 800px;
}

/* Front Panel - 前面板（带出票口）*/
.scale-front-panel {
  width: 100%;
  height: 35px;
  background: linear-gradient(180deg, #94a3b8 0%, #64748b 100%);
  border-bottom-left-radius: 10px;
  border-bottom-right-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  z-index: 5;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
}

/* 出票口 - 比小票宽一点 */
.receipt-slot {
  width: 260px;
  /* 比小票(240px)宽 */
  height: 10px;
  /* 竖向更宽 */
  background: #0a0f1a;
  border-radius: 5px;
  box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.9);
}

/* 小票动画容器 - 精准对齐出票口 */
.receipt-anim-container {
  position: absolute;
  top: 218px;
  left: 50%;
  transform: translateX(-50%);
  width: 240px;
  height: 400px;
  z-index: 9;
  pointer-events: none;
  overflow: hidden;
  /* 裁剪超出部分 */
}

/* 小票本身 */
.receipt-wrapper {
  width: 240px;
  background: linear-gradient(180deg, #fefefe 0%, #f9fafb 100%);
  padding: 14px 16px 20px;
  border-radius: 0;
  box-shadow:
    4px 4px 12px rgba(0, 0, 0, 0.15),
    8px 8px 24px rgba(0, 0, 0, 0.1),
    0 0 0 1px rgba(0, 0, 0, 0.02);
  position: relative;
  font-family: "Courier New", monospace;
  font-size: 0.75rem;
  color: #374151;
  transform: translateY(-300px);
  /* 固定值，确保完全隐藏 */
  opacity: 0;
  will-change: transform, opacity;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  transition:
    transform 0.6s cubic-bezier(0.25, 0.46, 0.45, 0.94),
    opacity 0.6s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

/* Receipt Animation States - 小票动画状态 */
.receipt-wrapper.printing {
  transform: translateY(0);
  opacity: 1;
}

.receipt-wrapper.discarding {
  transform: translateY(500px);
  /* 固定值，往下掉落 */
  opacity: 0;
  transition:
    transform 0.4s ease-in,
    opacity 0.3s ease;
}

/* 移除 discarding 后瞬间回到上方，无动画 */
.receipt-wrapper.reset-position {
  transition: none !important;
}

/* Input Styles */
.realtime-input {
  font-size: 1.5rem;
  padding: 16px 20px;
  border: 2px solid var(--border-color);
  border-radius: 16px;
  font-weight: 600;
  letter-spacing: 1px;
  background: rgba(255, 255, 255, 0.8);
  transition: all 0.3s ease;
}

.realtime-input:focus {
  border-color: var(--text-highlight);
  background: #fff;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.08);
}

/* Responsive - Electronic Scale */
@media (max-width: 900px) {
  .molar-tool-layout {
    grid-template-columns: 1fr;
  }

  .electronic-scale-wrapper {
    transform: rotateX(8deg) rotateZ(-2deg);
    width: 320px;
  }

  .molar-scale-stage {
    padding-bottom: 250px;
  }
}

/* Highlight Enter Key hint */
.enter-hint {
  font-size: 0.8rem;
  color: #475569;
  margin-top: 8px;
  text-align: right;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 4px;
  font-weight: 500;
}

.kbd-key {
  background: #e2e8f0;
  border: 1px solid #cbd5e1;
  border-radius: 4px;
  padding: 2px 8px;
  font-size: 0.75rem;
  font-weight: 600;
  color: #334155;
  box-shadow: 0 2px 0 #94a3b8;
}

/* ========================================
   Molar Mass - Learning Mode & Tooltips
   ======================================== */

/* Show Calculation Button */
.show-calc-btn {
  width: 100%;
  padding: 10px;
  background: #f1f5f9;
  color: #475569;
  border: 1px solid #cbd5e1;
  border-radius: 12px;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  margin-top: 10px;
}

.show-calc-btn:hover {
  background: #e2e8f0;
  color: #1e293b;
}

/* Calculation Steps Container */
.calc-steps-content {
  background: #ffffff;
  border: 1px solid #e2e8f0;
  border-radius: 12px;
  padding: 15px;
  margin-top: 10px;
  font-size: 0.9rem;
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
  animation: slideDown 0.3s ease-out;
}

@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.calc-step-row {
  display: flex;
  justify-content: space-between;
  padding: 6px 0;
  border-bottom: 1px dashed #f1f5f9;
}

.calc-step-row:last-child {
  border-bottom: none;
  font-weight: 700;
  color: #0f172a;
  padding-top: 10px;
  margin-top: 5px;
  border-top: 2px solid #e2e8f0;
}

.calc-step-formula {
  color: #64748b;
  font-family: "SF Mono", monospace;
  font-size: 0.85rem;
}


/* ============================================
   Molar Mass Calculator - Apple Style Tips
   ============================================ */
.formula-live-preview {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 14px;
  background: rgba(248, 250, 252, 0.6);
  border: 1px solid rgba(226, 232, 240, 0.6);
  border-radius: 12px;
  margin-top: 8px;
  min-height: 44px;
}

.formula-live-preview .preview-label {
  font-size: 0.75rem;
  font-weight: 600;
  color: #94a3b8;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  white-space: nowrap;
}

.formula-live-preview .preview-formula {
  font-size: 1.1rem;
  font-weight: 600;
  color: #1e293b;
  font-family:
    "SF Pro Display",
    -apple-system,
    BlinkMacSystemFont,
    sans-serif;
  letter-spacing: 0.02em;
}

.formula-live-preview .preview-formula sub {
  font-size: 0.9em;
  vertical-align: sub;
}

.formula-suggestion {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 12px;
  background: rgba(248, 250, 252, 0.6);
  border: 1px solid rgba(226, 232, 240, 0.6);
  border-radius: 10px;
  margin-top: 8px;
  font-size: 0.8rem;
  color: #94a3b8;
  transition: all 0.25s ease;
}

.formula-suggestion.has-message {
  background: #fffbeb;
  border-color: #fcd34d;
  color: #92400e;
}

.formula-suggestion.has-error {
  background: #fef2f2;
  border-color: #fca5a5;
  color: #991b1b;
}

.formula-suggestion.has-error .suggestion-icon {
  background: rgba(239, 68, 68, 0.15);
  color: #dc2626;
}

.formula-suggestion .suggestion-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 26px;
  background: rgba(234, 179, 8, 0.15);
  border-radius: 50%;
  color: #b45309;
  flex-shrink: 0;
}

.formula-suggestion .suggestion-icon svg {
  display: block;
}

.formula-suggestion .suggestion-text {
  line-height: 1.4;
}

/* Tips Section - Neutral glass float card */
.molar-tips-apple {
  background: rgba(248, 250, 252, 0.7);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  padding: 16px 20px;
  margin-top: 0;
  border-radius: 16px;
  border: 1px solid rgba(255, 255, 255, 0.6);
  box-shadow:
    0 2px 8px rgba(0, 0, 0, 0.04),
    0 8px 24px rgba(0, 0, 0, 0.08),
    inset 0 1px 0 rgba(255, 255, 255, 0.8);
  flex-grow: 1;
  transition: all 0.2s ease;
}

/* Tips header with icon */
.molar-tips-header {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.75rem;
  font-weight: 600;
  color: #64748b;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 8px;
}

.molar-tips-header svg {
  color: #94a3b8;
}

.molar-tips-apple .tips-item {
  display: block;
  padding: 5px 0;
  font-size: 0.8rem;
  color: #64748b;
  line-height: 1.5;
}

.molar-tips-apple .tips-item::before {
  content: "";
  display: inline-block;
  width: 5px;
  height: 5px;
  background: #94a3b8;
  border-radius: 50%;
  margin-right: 8px;
  vertical-align: middle;
}

.molar-tips-apple .tips-examples {
  margin-top: 16px;
  padding: 12px;
  background: #f8fafc;
  border-radius: 12px;
}

.molar-tips-apple .example-row {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 6px 0;
  font-size: 0.8rem;
}

.molar-tips-apple .example-row code {
  font-family: "SF Mono", "Monaco", monospace;
  font-size: 0.8rem;
  color: #475569;
  background: #fff;
  padding: 3px 8px;
  border-radius: 6px;
  border: 1px solid #e2e8f0;
  min-width: 90px;
}

.molar-tips-apple .example-row span {
  color: #94a3b8;
}

.molar-tips-apple .example-row .result {
  font-weight: 600;
  color: #1e293b;
  font-family:
    "SF Pro Display",
    -apple-system,
    sans-serif;
}

.molar-tips-apple .example-row .result sub {
  font-size: 0.7em;
  vertical-align: baseline;
  position: relative;
  top: 0.25em;
}