:root {
  --primary-color: #2563eb;
  --primary-hover: #1d4ed8;
  --secondary-color: #64748b;
  --background: #f8fafc;
  --surface: #ffffff;
  --border: #e2e8f0;
  --text-primary: #0f172a;
  --text-secondary: #64748b;
  --error: #dc2626;
  --success: #16a34a;
  --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background-color: var(--background);
  color: var(--text-primary);
  line-height: 1.6;
}

/* Utility Classes */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 1rem;
}

.btn {
  padding: 0.5rem 1rem;
  border: none;
  border-radius: 0.375rem;
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}

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

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

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

.btn-secondary:hover {
  opacity: 0.9;
}

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

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

.input {
  width: 100%;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 0.375rem;
  font-size: 0.875rem;
  transition: border-color 0.2s;
}

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

.card {
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: 0.5rem;
  padding: 1.5rem;
  box-shadow: var(--shadow);
}

.error-message {
  color: var(--error);
  font-size: 0.875rem;
  margin-top: 0.5rem;
}

.success-message {
  color: var(--success);
  font-size: 0.875rem;
  margin-top: 0.5rem;
}

/* Loading Spinner */
.spinner {
  border: 3px solid var(--border);
  border-top-color: var(--primary-color);
  border-radius: 50%;
  width: 2rem;
  height: 2rem;
  animation: spin 1s linear infinite;
}

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

/* Layout */
.app-layout {
  display: flex;
  height: 100vh;
  overflow: hidden;
}

.sidebar {
  width: 250px;
  background-color: var(--surface);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
}

.main-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.header {
  height: 60px;
  background-color: var(--surface);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  padding: 0 1rem;
  justify-content: space-between;
}

.content-area {
  flex: 1;
  overflow-y: auto;
  padding: 1rem;
}

/* Responsive */
@media (max-width: 768px) {
  .app-layout {
    flex-direction: column;
  }
  
  .sidebar {
    width: 100%;
    height: auto;
    border-right: none;
    border-bottom: 1px solid var(--border);
  }
}