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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: #f5f5f5;
  color: #333;
  min-height: 100vh;
}

header {
  display: flex;
  justify-content: flex-end;
  align-items: center;
  gap: 1rem;
  padding: 0.75rem 2rem;
  background: #fff;
  border-bottom: 1px solid #e0e0e0;
}

main {
  max-width: 600px;
  margin: 4rem auto;
  padding: 2rem;
  background: #fff;
  border-radius: 8px;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.08);
  text-align: center;
}

h1 {
  font-size: 1.75rem;
  margin-bottom: 0.75rem;
  color: #1a1a2e;
}

p {
  color: #555;
  margin-bottom: 1.5rem;
  line-height: 1.5;
}

.btn {
  display: inline-block;
  padding: 0.6rem 1.4rem;
  border-radius: 6px;
  text-decoration: none;
  font-weight: 500;
  background: #e8e8e8;
  color: #333;
  transition: background 0.15s;
}

.btn:hover {
  background: #d8d8d8;
}

.btn-primary {
  background: #0078d4;
  color: #fff;
}

.btn-primary:hover {
  background: #006cbe;
}

.btn:disabled,
.btn-primary:disabled {
  background: #c0c0c0;
  color: #fff;
  cursor: not-allowed;
}

.btn:disabled:hover,
.btn-primary:disabled:hover {
  background: #c0c0c0;
}

.btn-small {
  padding: 0.35rem 0.9rem;
  font-size: 0.85rem;
}