:root {
  --primary-color: #4a6fa5;
  --secondary-color: #166088;
  --accent-color: #4fc3a1;
  --background-color: #f8f9fa;
  --text-color: #333;
  --light-gray: #e9ecef;
  --medium-gray: #ced4da;
  --dark-gray: #6c757d;
  --success-color: #28a745;
  --warning-color: #ffc107;
  --danger-color: #dc3545;
}

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

body {
  font-family: 'Roboto', sans-serif;
  line-height: 1.6;
  color: var(--text-color);
  background-color: var(--background-color);
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

header {
  background-color: var(--primary-color);
  color: white;
  padding: 1rem 0;
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-size: 1.5rem;
  font-weight: bold;
}

.nav-links {
  display: flex;
  list-style: none;
}

.nav-links li {
  margin-left: 1.5rem;
}

.nav-links a {
  color: white;
  text-decoration: none;
  transition: color 0.3s;
}

.nav-links a:hover {
  color: var(--accent-color);
}

.btn {
  display: inline-block;
  padding: 0.5rem 1rem;
  background-color: var(--accent-color);
  color: white;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  font-size: 1rem;
  transition: background-color 0.3s;
}

.btn:hover {
  background-color: #3da58a;
}

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

.btn-secondary:hover {
  background-color: #124e6c;
}

.card {
  background-color: white;
  border-radius: 8px;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
}

.form-group {
  margin-bottom: 1rem;
}

label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 500;
}

input, textarea, select {
  width: 100%;
  padding: 0.75rem;
  border: 1px solid var(--medium-gray);
  border-radius: 4px;
  font-size: 1rem;
}

textarea {
  min-height: 200px;
  resize: vertical;
}

.word-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 1rem;
}

.word-card {
  border: 1px solid var(--light-gray);
  border-radius: 4px;
  padding: 1rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.word-actions {
  display: flex;
  gap: 0.5rem;
}

.badge {
  display: inline-block;
  padding: 0.25rem 0.5rem;
  border-radius: 20px;
  font-size: 0.75rem;
  font-weight: 500;
}

.badge-known {
  background-color: var(--success-color);
  color: white;
}

.badge-learning {
  background-color: var(--warning-color);
  color: var(--text-color);
}

.tab-container {
  margin-top: 1.5rem;
}

.tabs {
  display: flex;
  border-bottom: 1px solid var(--medium-gray);
  margin-bottom: 1rem;
}

.tab {
  padding: 0.75rem 1.5rem;
  cursor: pointer;
  border-bottom: 3px solid transparent;
}

.tab.active {
  border-bottom-color: var(--primary-color);
  font-weight: 500;
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

.loading {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100px;
}

.spinner {
  border: 4px solid rgba(0, 0, 0, 0.1);
  border-radius: 50%;
  border-top: 4px solid var(--primary-color);
  width: 30px;
  height: 30px;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

@media (max-width: 768px) {
  .word-list {
    grid-template-columns: 1fr;
  }
  
  .nav-links {
    display: none;
  }
}