:root {
  --color-primary: #4a90d9;
  --color-primary-light: #6ba3e0;
  --color-primary-dark: #3a7bc8;
  --color-bg: #f5f5f5;
  --color-card: #ffffff;
  --color-text: #333333;
  --color-text-secondary: #666666;
  --color-border: #e0e0e0;
  --color-highlight: #e8f0fe;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
  --transition: 0.2s ease;
}

html, body {
  margin: 0;
  padding: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background-color: var(--color-bg);
  color: var(--color-text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

header {
  margin: 0;
  padding: 0;
}

main {
  margin: 0;
  padding: 0;
  flex: 1;
}

footer {
  margin: 0;
  padding: 0;
}

div#app {
  max-width: 720px;
  margin: 0 auto;
  padding: 32px 20px 48px 20px;
}

#title {
  text-align: center;
  font-size: 28px;
  font-weight: 700;
  color: var(--color-text);
  margin: 0 0 8px 0;
}

#subtitle {
  text-align: center;
  font-size: 14px;
  color: var(--color-text-secondary);
  margin: 0 0 32px 0;
}

#converter {
  background: var(--color-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
  display: flex;
  align-items: flex-end;
  gap: 12px;
}

.input-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
  flex: 1;
  min-width: 0;
}

.input-label {
  font-size: 12px;
  font-weight: 600;
  color: var(--color-text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.input-field {
  width: 100%;
  box-sizing: border-box;
  height: 48px;
  font-size: 20px;
  font-weight: 500;
  padding: 0 14px;
  border: 2px solid var(--color-border);
  border-radius: var(--radius-sm);
  outline: none;
  transition: border-color var(--transition), box-shadow var(--transition);
  background: var(--color-card);
  color: var(--color-text);
}

.input-field:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(74, 144, 217, 0.15);
}

.input-field::placeholder {
  color: #bbbbbb;
}

.unit-select {
  width: 100%;
  box-sizing: border-box;
  height: 44px;
  font-size: 15px;
  padding: 0 10px;
  border: 2px solid var(--color-border);
  border-radius: var(--radius-sm);
  outline: none;
  background: var(--color-card);
  color: var(--color-text);
  cursor: pointer;
  transition: border-color var(--transition);
  appearance: auto;
}

.unit-select:focus {
  border-color: var(--color-primary);
}

#swap-btn-wrapper {
  display: flex;
  align-items: center;
  padding-bottom: 3px;
  flex-shrink: 0;
}

#swap-btn {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 2px solid var(--color-border);
  background: var(--color-card);
  font-size: 20px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-primary);
  transition: background var(--transition), border-color var(--transition), transform var(--transition);
  padding: 0;
  line-height: 1;
}

#swap-btn:hover {
  background: var(--color-highlight);
  border-color: var(--color-primary);
  transform: rotate(180deg);
}

#table-container {
  margin-top: 32px;
  display: none;
}

#table-container.visible {
  display: block;
}

#table-title {
  font-size: 18px;
  font-weight: 600;
  color: var(--color-text);
  margin: 0 0 16px 0;
}

#unit-table {
  display: grid;
  grid-template-columns: 1fr;
  gap: 6px;
}

.unit-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
  background: var(--color-card);
  border-radius: var(--radius-sm);
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.04);
  transition: background var(--transition);
}

.unit-row.highlight {
  background: var(--color-highlight);
  box-shadow: 0 1px 6px rgba(74, 144, 217, 0.12);
}

.unit-name {
  font-size: 14px;
  font-weight: 500;
  color: var(--color-text-secondary);
}

.unit-row.highlight .unit-name {
  color: var(--color-primary-dark);
  font-weight: 600;
}

.unit-value {
  font-size: 14px;
  font-weight: 600;
  color: var(--color-text);
  font-variant-numeric: tabular-nums;
}

.unit-row.highlight .unit-value {
  color: var(--color-primary-dark);
}

#info-section {
  margin-top: 40px;
}

#info-section h2 {
  font-size: 20px;
  font-weight: 700;
  color: var(--color-text);
  margin: 0 0 12px 0;
}

#intro {
  background: var(--color-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
  margin-bottom: 24px;
}

#intro p {
  font-size: 14px;
  line-height: 1.8;
  color: var(--color-text-secondary);
  margin: 0 0 12px 0;
}

#intro p:last-child {
  margin-bottom: 0;
}

#intro p strong {
  color: var(--color-primary-dark);
}

#scenarios {
  background: var(--color-card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
}

.scenario-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.scenario-card {
  background: var(--color-bg);
  border-radius: var(--radius-sm);
  padding: 16px;
  transition: background var(--transition), box-shadow var(--transition);
}

.scenario-card:hover {
  background: var(--color-highlight);
  box-shadow: 0 2px 8px rgba(74, 144, 217, 0.1);
}

.scenario-icon {
  font-size: 24px;
  display: block;
  margin-bottom: 6px;
}

.scenario-card h3 {
  font-size: 15px;
  font-weight: 600;
  color: var(--color-text);
  margin: 0 0 6px 0;
}

.scenario-card p {
  font-size: 13px;
  line-height: 1.6;
  color: var(--color-text-secondary);
  margin: 0;
}

footer {
  text-align: center;
  padding: 20px 0;
}

.page-info {
  font-size: 12px;
  color: var(--color-text-secondary);
}

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

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

@media (max-width: 768px) {
  #converter {
    flex-direction: column;
    align-items: stretch;
    gap: 16px;
    padding: 20px;
  }

  #swap-btn-wrapper {
    justify-content: center;
    padding-bottom: 0;
  }

  #swap-btn {
    transform: rotate(90deg);
  }

  #swap-btn:hover {
    transform: rotate(270deg);
  }

  div#app {
    padding: 20px 12px 32px 12px;
  }

  #title {
    font-size: 24px;
  }

  .scenario-grid {
    grid-template-columns: 1fr;
  }

  #intro,
  #scenarios {
    padding: 20px;
  }
}