:root {
  --primary-color: #2563eb;
  --primary-hover: #1d4ed8;
  --bg-color: #f8fafc;
  --text-color: #1e293b;
  --border-color: #e2e8f0;
  --error-color: #ef4444;
  --success-color: #10b981;
  --card-bg: #ffffff;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.5;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

header {
  background-color: var(--card-bg);
  padding: 1rem 2rem;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

main {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 2rem;
}

footer {
  padding: 1rem;
  text-align: center;
  font-size: 0.875rem;
  color: #64748b;
}

article {
  background: var(--card-bg);
  padding: 2.5rem;
  border-radius: 0.75rem;
  box-shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  width: 100%;
  max-width: 400px;
}

h1 {
  margin-bottom: 1.5rem;
  font-size: 1.5rem;
  font-weight: 700;
  text-align: center;
}

form {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

section {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

label {
  font-weight: 500;
  font-size: 0.875rem;
}

input {
  padding: 0.625rem;
  border: 1px solid var(--border-color);
  border-radius: 0.375rem;
  font-size: 1rem;
  width: 100%;
}

input:focus {
  outline: 2px solid var(--primary-color);
  outline-offset: -1px;
}

button {
  background-color: var(--primary-color);
  color: white;
  padding: 0.625rem;
  border: none;
  border-radius: 0.375rem;
  font-weight: 600;
  cursor: pointer;
  transition: background-color 0.2s;
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 0.5rem;
}

button:hover:not(:disabled) {
  background-color: var(--primary-hover);
}

button:disabled {
  opacity: 0.7;
  cursor: not-allowed;
}

.error-message {
  color: var(--error-color);
  background-color: #fee2e2;
  padding: 0.75rem;
  border-radius: 0.375rem;
  margin-bottom: 1rem;
  font-size: 0.875rem;
}

.success-message {
  color: var(--success-color);
  background-color: #dcfce7;
  padding: 0.75rem;
  border-radius: 0.375rem;
  margin-bottom: 1rem;
  font-size: 0.875rem;
}

.spinner {
  width: 1rem;
  height: 1rem;
  border: 2px solid #ffffff33;
  border-top-color: #fff;
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
  display: none;
}

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

button.loading .spinner {
  display: inline-block;
}

nav {
  display: flex;
  gap: 1rem;
}

nav a {
  text-decoration: none;
  color: var(--primary-color);
  font-size: 0.875rem;
}

nav a:hover {
  text-decoration: underline;
}

img.qr-code {
  display: block;
  margin: 1.5rem auto;
  border: 1px solid var(--border-color);
  border-radius: 0.5rem;
}

code {
  background: #f1f5f9;
  padding: 0.2rem 0.4rem;
  border-radius: 0.25rem;
  font-family: monospace;
}