:root {
  --color-primary: #1a5276;
  --color-accent: #2e86c1;
  --color-bg: #f8f9fa;
  --color-surface: #ffffff;
  --color-text: #2c3e50;
  --color-text-light: #7f8c8d;
  --color-border: #dee2e6;
  --color-row-alt: #f1f3f5;
  --radius: 8px;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
  --font-stack: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: var(--font-stack);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
}

header {
  text-align: center;
  padding: 1.5rem 1rem 0.5rem;
  width: 100%;
}

header h1 {
  font-size: 1.5rem;
  color: var(--color-primary);
  font-weight: 700;
  letter-spacing: -0.02em;
}

.subtitle {
  font-size: 0.9rem;
  color: var(--color-text-light);
  margin-top: 0.25rem;
}

main {
  width: 100%;
  max-width: 480px;
  padding: 1rem;
  flex: 1;
}

/* Rate hero */
.rate-hero {
  background: var(--color-surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 2rem 1.5rem;
  text-align: center;
  margin-bottom: 1.5rem;
}

.rate-label {
  display: block;
  font-size: 0.9rem;
  color: var(--color-text-light);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.rate-value {
  display: block;
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1.2;
  margin: 0.25rem 0;
}

.rate-currency {
  display: block;
  font-size: 1rem;
  color: var(--color-text-light);
  margin-bottom: 0.75rem;
}

.rate-timestamp {
  font-size: 0.8rem;
  color: var(--color-text-light);
}

.retry-btn {
  display: none;
  margin-top: 0.75rem;
  padding: 0.5rem 1.25rem;
  border: 1px solid var(--color-accent);
  border-radius: var(--radius);
  background: transparent;
  color: var(--color-accent);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
}

.retry-btn:hover {
  background: var(--color-accent);
  color: #fff;
}

.rate-hero.error .rate-value {
  color: #c0392b;
  font-size: 1.25rem;
  font-weight: 600;
}

.rate-hero.error .retry-btn {
  display: inline-block;
}

.rate-hero.loading .rate-value::after {
  content: "";
  display: inline-block;
  width: 1.5rem;
  height: 1.5rem;
  border: 3px solid var(--color-border);
  border-top-color: var(--color-accent);
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

.rate-hero.loading .rate-value {
  font-size: 0;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* Slider converter */
.slider-converter {
  background: var(--color-surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1.5rem;
  text-align: center;
}

.slider-converter h2 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: 0.75rem;
}

.slider-row {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 0.5rem;
}

.slider-row input[type="range"] {
  flex: 1;
  -webkit-appearance: none;
  appearance: none;
  height: 6px;
  background: var(--color-border);
  border-radius: 3px;
  outline: none;
}

.slider-row input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--color-accent);
  cursor: pointer;
  border: 2px solid #fff;
  box-shadow: 0 1px 4px rgba(0,0,0,0.2);
}

.slider-row input[type="range"]::-moz-range-thumb {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--color-accent);
  cursor: pointer;
  border: 2px solid #fff;
  box-shadow: 0 1px 4px rgba(0,0,0,0.2);
}

.slider-value {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-text);
  min-width: 5rem;
  text-align: right;
  font-variant-numeric: tabular-nums;
}

.slider-result {
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--color-primary);
  font-variant-numeric: tabular-nums;
}

/* Conversion table */
.conversion-table {
  background: var(--color-surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
}

.conversion-table h2 {
  font-size: 1rem;
  font-weight: 600;
  padding: 1rem 1.25rem 0.5rem;
  color: var(--color-primary);
}

table {
  width: 100%;
  border-collapse: collapse;
}

thead th {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-light);
  padding: 0.5rem 1.25rem;
  border-bottom: 2px solid var(--color-border);
  text-align: left;
}

tbody td {
  padding: 0.65rem 1.25rem;
  border-bottom: 1px solid var(--color-border);
  font-variant-numeric: tabular-nums;
}

tbody tr:nth-child(even) {
  background: var(--color-row-alt);
}

tbody tr:last-child td {
  border-bottom: none;
}

td:nth-child(2) {
  font-weight: 600;
  color: var(--color-primary);
  text-align: right;
}

/* Footer */
footer {
  text-align: center;
  padding: 1rem;
  font-size: 0.8rem;
  color: var(--color-text-light);
  width: 100%;
}

/* Tablet */
@media (min-width: 768px) {
  header h1 {
    font-size: 1.75rem;
  }

  main {
    max-width: 600px;
    padding: 1.5rem;
  }

  .rate-hero {
    padding: 2.5rem 2rem;
  }

  .rate-value {
    font-size: 3rem;
  }

  thead th,
  tbody td {
    padding: 0.75rem 1.5rem;
  }

  .slider-result {
    font-size: 2rem;
  }
}

/* Desktop */
@media (min-width: 1024px) {
  main {
    max-width: 680px;
  }

  .rate-value {
    font-size: 3.5rem;
  }
}