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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  line-height: 1.6;
  min-height: 100vh;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem;
}

header {
  text-align: center;
  margin-bottom: 3rem;
  position: relative;
}

#theme-toggle {
  position: absolute;
  top: 0;
  right: 0;
  background: transparent;
  border: 1px solid currentColor;
  border-radius: 6px;
  cursor: pointer;
  padding: 0.4rem;
  opacity: 0.5;
  transition: opacity 0.2s ease;
  color: inherit;
  display: flex;
  align-items: center;
  justify-content: center;
}

#theme-toggle:hover {
  opacity: 1;
}

header h1 {
  font-size: 2.5rem;
  margin-bottom: 0.5rem;
}

header p {
  font-size: 1.1rem;
  opacity: 0.8;
}

.provider-section {
  margin-bottom: 2.5rem;
}

.provider-heading {
  font-size: 1.5rem;
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
}

.cert-list {
  list-style: none;
}

.cert-item {
  display: grid;
  grid-template-columns: 1fr auto auto auto;
  gap: 1rem;
  align-items: center;
  padding: 1rem;
  margin-bottom: 0.5rem;
}

.cert-name {
  font-weight: 600;
}

.cert-number {
  font-family: 'Courier New', monospace;
  font-size: 0.9rem;
}

.cert-date {
  font-size: 0.9rem;
}

.cert-verify {
  text-decoration: none;
  padding: 0.4rem 0.8rem;
  border-radius: 4px;
  font-size: 0.85rem;
  font-weight: 500;
  transition: all 0.2s ease;
}

.error {
  text-align: center;
  color: #dc3545;
  padding: 2rem;
}

footer {
  text-align: center;
  padding: 2rem;
  margin-top: 2rem;
  font-size: 0.9rem;
  opacity: 0.7;
}

@media (max-width: 768px) {
  .container {
    padding: 1.5rem 1rem;
  }

  header h1 {
    font-size: 1.8rem;
  }

  header p {
    font-size: 1rem;
  }

  .provider-heading {
    font-size: 1.2rem;
  }

  .cert-item {
    grid-template-columns: 1fr;
    gap: 0.4rem;
    padding: 1rem;
  }

  .cert-name {
    font-size: 1rem;
  }

  .cert-number {
    font-size: 0.8rem;
    word-break: break-all;
  }

  .cert-date {
    font-size: 0.85rem;
  }

  .cert-verify {
    justify-self: start;
    margin-top: 0.5rem;
    padding: 0.5rem 1rem;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 1rem 0.75rem;
  }

  header {
    margin-bottom: 2rem;
  }

  header h1 {
    font-size: 1.5rem;
  }

  .provider-section {
    margin-bottom: 1.5rem;
  }

  .cert-item {
    padding: 0.75rem;
  }
}