html, body, main, header, footer {
  padding: 0px;
  margin: 0px;
}

/* Material 3 Purple Theme Variables */
:root {
  --md-primary: #6750a4;
  --md-on-primary: #ffffff;
  --md-primary-container: #eaddff;
  --md-on-primary-container: #21005d;
  --md-surface: #fef7ff;
  --md-surface-variant: #e7e0ec;
  --md-on-surface: #1d1b20;
  --md-on-surface-variant: #49454f;
  --md-outline: #79747e;
  --md-error: #b3261e;
  --md-error-container: #f9dedc;
  --md-on-error: #ffffff;
  --md-success: #1b7a35;
  --md-success-container: #d9f4e1;
}

body {
  font-family: "Roboto", "Noto Sans SC", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background-color: #f5f0fa;
  color: var(--md-on-surface);
  line-height: 1.6;
}

/* Header */
header {
  text-align: center;
  padding: 24px 16px 12px;
}

#page-title {
  font-size: 1.8rem;
  color: var(--md-primary);
  margin: 16px 0 4px;
  font-weight: 700;
}

#page-subtitle {
  font-size: 0.95rem;
  color: var(--md-on-surface-variant);
  margin: 0 0 8px;
}

/* Ad Slot */
.ad-slot {
  margin: 0 auto 8px;
  max-width: 720px;
}

/* Main App Container */
#app {
  max-width: 600px;
  margin: 0 auto;
  padding: 16px;
  background: var(--md-surface);
  border-radius: 16px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08), 0 4px 12px rgba(103, 80, 164, 0.08);
}

/* Tab Bar */
#tab-bar {
  display: flex;
  gap: 4px;
  margin-bottom: 24px;
  background: var(--md-surface-variant);
  border-radius: 12px;
  padding: 4px;
}

.tab-btn {
  flex: 1;
  padding: 10px 8px;
  border: none;
  border-radius: 8px;
  background: transparent;
  color: var(--md-on-surface-variant);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.2s, color 0.2s;
  min-height: 44px;
  touch-action: manipulation;
}

.tab-btn.active {
  background: var(--md-primary);
  color: var(--md-on-primary);
  box-shadow: 0 1px 3px rgba(103, 80, 164, 0.3);
}

.tab-btn:hover:not(.active) {
  background: rgba(103, 80, 164, 0.08);
}

/* Tab Panels */
.tab-panel {
  display: none;
  animation: fadeIn 0.2s ease;
}

.tab-panel.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Solve Grid */
#solve-grid {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto 1fr auto 1fr;
  align-items: center;
  gap: 8px;
  margin-bottom: 12px;
}

.grid-cell {
  position: relative;
}

.grid-sep, .grid-sep-eq {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--md-primary);
  text-align: center;
  padding: 0 2px;
  user-select: none;
}

.grid-sep-eq {
  font-size: 1.2rem;
}

.ratio-input {
  width: 100%;
  box-sizing: border-box;
  padding: 12px 8px;
  border: 2px solid var(--md-outline);
  border-radius: 8px;
  font-size: 1.1rem;
  text-align: center;
  background: #fff;
  color: var(--md-on-surface);
  transition: border-color 0.2s, box-shadow 0.2s;
  min-height: 44px;
  touch-action: manipulation;
}

.ratio-input:focus {
  outline: none;
  border-color: var(--md-primary);
  box-shadow: 0 0 0 3px rgba(103, 80, 164, 0.15);
}

.ratio-input.error {
  border-color: var(--md-error);
  box-shadow: 0 0 0 3px rgba(179, 38, 30, 0.12);
}

/* Text Inputs */
.text-input {
  width: 100%;
  box-sizing: border-box;
  padding: 12px 16px;
  border: 2px solid var(--md-outline);
  border-radius: 8px;
  font-size: 1rem;
  background: #fff;
  color: var(--md-on-surface);
  transition: border-color 0.2s, box-shadow 0.2s;
  min-height: 44px;
  touch-action: manipulation;
}

.text-input:focus {
  outline: none;
  border-color: var(--md-primary);
  box-shadow: 0 0 0 3px rgba(103, 80, 164, 0.15);
}

.text-input.error {
  border-color: var(--md-error);
  box-shadow: 0 0 0 3px rgba(179, 38, 30, 0.12);
}

/* Error & Result Messages */
.error-msg {
  color: var(--md-error);
  font-size: 0.85rem;
  min-height: 20px;
  margin: 4px 0 8px;
  padding: 0 4px;
}

.result-msg {
  color: var(--md-success);
  font-size: 1.05rem;
  min-height: 20px;
  margin: 4px 0 12px;
  padding: 8px 12px;
  background: var(--md-success-container);
  border-radius: 8px;
  font-weight: 500;
  display: none;
}

.result-msg.visible {
  display: block;
}

/* Action Buttons */
.action-btn {
  display: block;
  width: 100%;
  padding: 14px 24px;
  border: none;
  border-radius: 12px;
  background: var(--md-primary);
  color: var(--md-on-primary);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  min-height: 44px;
  touch-action: manipulation;
  transition: background 0.2s, box-shadow 0.2s;
}

.action-btn:hover {
  background: #5a3ea3;
  box-shadow: 0 2px 8px rgba(103, 80, 164, 0.3);
}

.action-btn:active {
  background: #4e3591;
}

/* Simplify Panel */
#simplify-input-row {
  display: flex;
  gap: 8px;
  margin-bottom: 4px;
}

#simplify-input-row .text-input {
  flex: 1;
}

#simplify-input-row .action-btn {
  width: auto;
  white-space: nowrap;
  padding: 12px 20px;
}

/* Chain Panel */
#chain-input-rows {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 4px;
}

.chain-row {
  display: flex;
  align-items: center;
  gap: 8px;
}

.chain-row label {
  min-width: 56px;
  font-weight: 600;
  color: var(--md-on-surface-variant);
  font-size: 0.9rem;
}

.chain-row .text-input {
  flex: 1;
}

/* Extended Sections */
#__fork {
  text-align: center;
  margin: 32px auto 0;
  max-width: 600px;
  padding: 0 16px;
}

#__fork button {
  padding: 12px 32px;
  border: 2px solid var(--md-primary);
  border-radius: 12px;
  background: var(--md-on-primary);
  color: var(--md-primary);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  min-height: 44px;
  touch-action: manipulation;
  transition: background 0.2s, color 0.2s;
}

#__fork button:hover {
  background: var(--md-primary);
  color: var(--md-on-primary);
}

#features, #scenarios, #FAQ {
  max-width: 600px;
  margin: 32px auto;
  padding: 20px 24px;
  background: var(--md-surface);
  border-radius: 16px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06), 0 2px 8px rgba(103, 80, 164, 0.06);
}

#features h2, #scenarios h2, #FAQ h2 {
  font-size: 1.3rem;
  color: var(--md-primary);
  margin: 0 0 12px;
  font-weight: 700;
}

#features p {
  font-size: 0.95rem;
  color: var(--md-on-surface-variant);
  margin: 0;
  line-height: 1.8;
}

#scenarios ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

#scenarios li {
  font-size: 0.95rem;
  color: var(--md-on-surface-variant);
  padding: 8px 0;
  border-bottom: 1px solid #ece6f4;
  line-height: 1.6;
}

#scenarios li:last-child {
  border-bottom: none;
}

#FAQ dl {
  margin: 0;
}

#FAQ dt {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--md-on-surface);
  margin: 16px 0 4px;
  padding: 0;
}

#FAQ dt:first-child {
  margin-top: 0;
}

#FAQ dd {
  font-size: 0.9rem;
  color: var(--md-on-surface-variant);
  margin: 0 0 8px;
  padding: 0 0 0 16px;
  border-left: 3px solid var(--md-primary-container);
  line-height: 1.7;
}

/* Footer */
footer {
  text-align: center;
  padding: 24px 16px;
  font-size: 0.85rem;
  color: var(--md-on-surface-variant);
}

.page-info a {
  color: var(--md-primary);
  text-decoration: none;
}

.page-info a:hover {
  text-decoration: underline;
}

/* Responsive */
@media (max-width: 480px) {
  #page-title {
    font-size: 1.4rem;
  }

  #page-subtitle {
    font-size: 0.85rem;
  }

  #app {
    margin: 0 8px;
    padding: 12px;
    border-radius: 12px;
  }

  .tab-btn {
    font-size: 0.8rem;
    padding: 8px 4px;
  }

  #solve-grid {
    gap: 4px;
  }

  .ratio-input {
    font-size: 0.95rem;
    padding: 10px 4px;
  }

  .grid-sep, .grid-sep-eq {
    font-size: 1.2rem;
  }

  #simplify-input-row {
    flex-direction: column;
  }

  #simplify-input-row .action-btn {
    width: 100%;
  }

  .chain-row {
    flex-direction: column;
    align-items: stretch;
  }

  .chain-row label {
    min-width: auto;
  }

  #features, #scenarios, #FAQ {
    margin: 20px 8px;
    padding: 16px;
  }
}