/* ===== CSS Variables ===== */
:root {
  --color-primary: #2563eb;
  --color-primary-hover: #1d4ed8;
  --color-secondary: #64748b;
  --color-success: #10b981;
  --color-error: #ef4444;
  --color-bg: #ffffff;
  --color-bg-secondary: #f8fafc;
  --color-text: #1e293b;
  --color-text-secondary: #64748b;
  --color-border: #e2e8f0;

  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;

  --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 2rem;

  --border-radius: 0.5rem;
  --border-radius-lg: 0.75rem;
  --box-shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1);
  --box-shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);

  --transition: all 0.2s ease;
}

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

/* ===== Typography ===== */
body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg-secondary);
}

h1 {
  font-size: var(--font-size-3xl);
  font-weight: 700;
  margin-bottom: var(--spacing-lg);
  color: var(--color-text);
}

h2 {
  font-size: var(--font-size-2xl);
  font-weight: 600;
  margin-bottom: var(--spacing-md);
}

h3 {
  font-size: var(--font-size-xl);
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
}

p {
  margin-bottom: var(--spacing-md);
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: var(--transition);
}

a:hover {
  color: var(--color-primary-hover);
  text-decoration: underline;
}

/* ===== Layout ===== */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--spacing-xl);
}

.container-narrow {
  max-width: 600px;
  margin: 0 auto;
  padding: var(--spacing-xl);
}

/* ===== Header ===== */
.header {
  background-color: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  padding: var(--spacing-md) 0;
  margin-bottom: var(--spacing-2xl);
}

.header-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-xl);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
}

.logo:hover {
  text-decoration: none;
}

.nav {
  display: flex;
  gap: var(--spacing-lg);
  align-items: center;
}

.nav a, .nav button {
  color: var(--color-text-secondary);
  font-size: var(--font-size-base);
}

.nav a:hover, .nav button:hover {
  color: var(--color-text);
}

/* ===== Buttons ===== */
.btn {
  display: inline-block;
  padding: var(--spacing-sm) var(--spacing-lg);
  font-size: var(--font-size-base);
  font-weight: 500;
  text-align: center;
  border: none;
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: var(--transition);
  text-decoration: none;
}

.btn-primary {
  background-color: var(--color-primary);
  color: white;
}

.btn-primary:hover {
  background-color: var(--color-primary-hover);
  text-decoration: none;
}

.btn-secondary {
  background-color: var(--color-secondary);
  color: white;
}

.btn-secondary:hover {
  background-color: #475569;
}

.btn-danger {
  background-color: var(--color-error);
  color: white;
}

.btn-danger:hover {
  background-color: #dc2626;
}

.btn-outline {
  background-color: transparent;
  border: 1px solid var(--color-border);
  color: var(--color-text);
}

.btn-outline:hover {
  background-color: var(--color-bg-secondary);
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* ===== Forms ===== */
.form-group {
  margin-bottom: var(--spacing-lg);
}

.form-group label {
  display: block;
  margin-bottom: var(--spacing-xs);
  font-weight: 500;
  color: var(--color-text);
}

.form-group input,
.form-group textarea,
.form-group select {
  width: 100%;
  padding: var(--spacing-sm) var(--spacing-md);
  font-size: var(--font-size-base);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  background-color: var(--color-bg);
  transition: var(--transition);
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* ===== Cards ===== */
.card {
  background-color: var(--color-bg);
  border-radius: var(--border-radius-lg);
  box-shadow: var(--box-shadow);
  padding: var(--spacing-xl);
  margin-bottom: var(--spacing-lg);
}

.auth-card {
  max-width: 400px;
  margin: 4rem auto;
  background-color: var(--color-bg);
  border-radius: var(--border-radius-lg);
  box-shadow: var(--box-shadow-lg);
  padding: var(--spacing-2xl);
}

.auth-card h1 {
  text-align: center;
  margin-bottom: var(--spacing-sm);
}

.auth-card h2 {
  text-align: center;
  font-size: var(--font-size-xl);
  margin-bottom: var(--spacing-xl);
  color: var(--color-text-secondary);
}

.auth-link {
  text-align: center;
  margin-top: var(--spacing-lg);
  color: var(--color-text-secondary);
}

/* ===== Messages ===== */
.error-message {
  background-color: #fee2e2;
  border: 1px solid #fecaca;
  color: #991b1b;
  padding: var(--spacing-md);
  border-radius: var(--border-radius);
  margin-bottom: var(--spacing-lg);
}

.success-message {
  background-color: #d1fae5;
  border: 1px solid #a7f3d0;
  color: #065f46;
  padding: var(--spacing-md);
  border-radius: var(--border-radius);
  margin-bottom: var(--spacing-lg);
}

/* ===== Loader ===== */
.loader {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.5);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 9999;
}

.spinner {
  width: 50px;
  height: 50px;
  border: 4px solid rgba(255, 255, 255, 0.3);
  border-top-color: white;
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

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

/* ===== Responsive ===== */
@media (max-width: 640px) {
  .container {
    padding: var(--spacing-md);
  }

  .auth-card {
    margin: 2rem auto;
    padding: var(--spacing-xl);
  }

  h1 {
    font-size: var(--font-size-2xl);
  }

  h2 {
    font-size: var(--font-size-xl);
  }
}