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

:root {
  --bg: #0f1117;
  --surface: #1a1d27;
  --surface-hover: #22263a;
  --border: #2a2d3e;
  --text-primary: #e2e8f0;
  --text-secondary: #94a3b8;
  --accent: #6366f1;
  --accent-hover: #818cf8;
  --green: #22c55e;
  --red: #ef4444;
  --radius: 12px;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.4);
}

body {
  background-color: var(--bg);
  color: var(--text-primary);
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header */
.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 2rem;
  background-color: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header__brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.header__logo {
  font-size: 1.75rem;
  color: var(--accent);
}

.header__title {
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.header__controls {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

.currency-selector {
  background-color: var(--surface-hover);
  border: 1px solid var(--border);
  color: var(--text-primary);
  padding: 0.4rem 0.75rem;
  border-radius: 8px;
  font-size: 0.9rem;
  cursor: pointer;
  outline: none;
  transition: border-color 0.2s;
}

.currency-selector:hover {
  border-color: var(--accent);
}

.refresh-info {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.refresh-info__countdown {
  font-weight: 700;
  color: var(--accent);
  min-width: 2.5rem;
  text-align: right;
}

.user-info {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.user-info__name {
  font-size: 0.85rem;
  color: var(--text-secondary);
  font-weight: 600;
}

.logout-btn {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-secondary);
  padding: 0.35rem 0.75rem;
  border-radius: 8px;
  font-size: 0.8rem;
  cursor: pointer;
  transition: all 0.2s;
}

.logout-btn:hover {
  border-color: var(--red);
  color: var(--red);
}

/* Main */
.main {
  flex: 1;
  padding: 2rem;
  max-width: 1400px;
  margin: 0 auto;
  width: 100%;
}

/* Cards */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 1.25rem;
}

.crypto-card {
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  cursor: pointer;
  transition: transform 0.2s, border-color 0.2s, box-shadow 0.2s;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.crypto-card:hover {
  transform: translateY(-4px);
  border-color: var(--accent);
  box-shadow: var(--shadow);
}

.crypto-card.active {
  border-color: var(--accent);
  background-color: var(--surface-hover);
}

.card__header {
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

.card__icon {
  width: 32px;
  height: 32px;
  border-radius: 50%;
}

.card__name {
  font-weight: 600;
  font-size: 0.95rem;
}

.card__symbol {
  font-size: 0.75rem;
  color: var(--text-secondary);
  text-transform: uppercase;
}

.card__price {
  font-size: 1.4rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.card__change {
  font-size: 0.85rem;
  font-weight: 600;
  padding: 0.2rem 0.5rem;
  border-radius: 6px;
  width: fit-content;
}

.card__change--positive {
  color: var(--green);
  background-color: rgba(34, 197, 94, 0.1);
}

.card__change--negative {
  color: var(--red);
  background-color: rgba(239, 68, 68, 0.1);
}

.cards-error {
  grid-column: 1 / -1;
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-left: 3px solid var(--red);
  border-radius: var(--radius);
  padding: 1rem 1.25rem;
  color: var(--text-secondary);
  font-size: 0.95rem;
}

/* Skeleton */
.skeleton-card {
  background: linear-gradient(90deg, var(--surface) 25%, var(--surface-hover) 50%, var(--surface) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: var(--radius);
  height: 160px;
  border: 1px solid var(--border);
}

@keyframes shimmer {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* Chart */
.chart-section {
  margin-top: 2rem;
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

.chart-section.hidden {
  display: none;
}

.chart-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}

.chart-title {
  font-size: 1.1rem;
  font-weight: 700;
  flex: 1;
}

.chart-controls {
  display: flex;
  gap: 0.5rem;
}

.chart-range-btn {
  background-color: var(--surface-hover);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  padding: 0.35rem 0.75rem;
  border-radius: 8px;
  font-size: 0.8rem;
  cursor: pointer;
  transition: all 0.2s;
}

.chart-range-btn:hover,
.chart-range-btn.active {
  background-color: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.chart-close {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-secondary);
  width: 32px;
  height: 32px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.9rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
}

.chart-close:hover {
  border-color: var(--red);
  color: var(--red);
}

.chart-wrapper {
  position: relative;
  height: 320px;
}

/* Footer */
.footer {
  text-align: center;
  padding: 1.25rem;
  font-size: 0.8rem;
  color: var(--text-secondary);
  border-top: 1px solid var(--border);
}

.footer a {
  color: var(--accent);
  text-decoration: none;
}

.footer a:hover {
  text-decoration: underline;
}

/* Responsive */
@media (max-width: 640px) {
  .header {
    padding: 1rem;
    flex-wrap: wrap;
    gap: 0.75rem;
  }

  .main {
    padding: 1rem;
  }

  .cards-grid {
    grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
  }
}