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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
}

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

/* Header Styles */
header {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 20px 0;
    box-shadow: 0 2px 20px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

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

.logo {
    font-size: 28px;
    font-weight: bold;
    text-decoration: none;
    color: #2c3e50;
    display: flex;
    align-items: center;
    gap: 10px;
}

.logo-icon {
    color: #3498db;
}

nav ul {
    display: flex;
    list-style: none;
    gap: 30px;
}

nav a {
    text-decoration: none;
    color: #2c3e50;
    font-weight: 600;
    padding: 8px 16px;
    border-radius: 25px;
    transition: all 0.3s ease;
}

nav a:hover {
    background: #3498db;
    color: white;
}

/* Hero Section */
.hero {
    text-align: center;
    padding: 80px 0;
    color: white;
}

.hero h1 {
    font-size: 3.5rem;
    margin-bottom: 20px;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

.hero p {
    font-size: 1.2rem;
    max-width: 700px;
    margin: 0 auto 30px;
    opacity: 0.9;
}

.btn {
    display: inline-block;
    background: #3498db;
    color: white;
    padding: 12px 30px;
    border-radius: 25px;
    text-decoration: none;
    font-weight: bold;
    transition: all 0.3s ease;
    border: 2px solid #3498db;
}

.btn:hover {
    background: transparent;
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0,0,0,0.2);
}

.btn-secondary {
    background: transparent;
    border: 2px solid white;
    margin-left: 15px;
}

.btn-secondary:hover {
    background: white;
    color: #3498db;
}

/* Features Section */
.features {
    padding: 80px 0;
    background: white;
}

.section-title {
    text-align: center;
    margin-bottom: 50px;
}

.section-title h2 {
    font-size: 2.5rem;
    color: #2c3e50;
    margin-bottom: 15px;
}

.section-title p {
    color: #7f8c8d;
    max-width: 600px;
    margin: 0 auto;
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
}

.feature-card {
    background: #f8f9fa;
    padding: 30px;
    border-radius: 15px;
    text-align: center;
    transition: transform 0.3s ease;
    box-shadow: 0 5px 15px rgba(0,0,0,0.1);
}

.feature-card:hover {
    transform: translateY(-5px);
}

.feature-icon {
    font-size: 3rem;
    color: #3498db;
    margin-bottom: 20px;
}

.feature-card h3 {
    color: #2c3e50;
    margin-bottom: 15px;
}

/* Vocabulary Section */
.vocabulary-section {
    padding: 80px 0;
    background: #f8f9fa;
}

.vocab-container {
    max-width: 800px;
    margin: 0 auto;
    background: white;
    padding: 40px;
    border-radius: 20px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
}

.vocab-display {
    text-align: center;
    margin-bottom: 30px;
}

.current-word {
    font-size: 3rem;
    font-weight: bold;
    color: #2c3e50;
    margin-bottom: 10px;
}

.word-definition {
    font-size: 1.2rem;
    color: #7f8c8d;
    margin-bottom: 20px;
}

.word-example {
    font-style: italic;
    color: #555;
    margin-bottom: 20px;
    padding: 15px;
    background: #f1f8ff;
    border-radius: 10px;
}

.vocab-controls {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin-top: 20px;
}

.vocab-btn {
    padding: 12px 25px;
    border: none;
    border-radius: 25px;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.3s ease;
}

.known-btn {
    background: #27ae60;
    color: white;
}

.known-btn:hover {
    background: #219a52;
}

.unknown-btn {
    background: #e74c3c;
    color: white;
}

.unknown-btn:hover {
    background: #c0392b;
}

.progress-bar {
    width: 100%;
    height: 10px;
    background: #ecf0f1;
    border-radius: 5px;
    margin-top: 20px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: #3498db;
    transition: width 0.3s ease;
}

/* Footer */
footer {
    background: #2c3e50;
    color: white;
    padding: 40px 0;
    text-align: center;
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 20px;
}

.footer-links a {
    color: #bdc3c7;
    text-decoration: none;
    margin: 0 15px;
    transition: color 0.3s ease;
}

.footer-links a:hover {
    color: white;
}

.copyright {
    color: #bdc3c7;
    margin-top: 20px;
}

/* Responsive Design */
@media (max-width: 768px) {
    .hero h1 {
        font-size: 2.5rem;
    }
    
    .header-content {
        flex-direction: column;
        gap: 20px;
    }
    
    nav ul {
        gap: 15px;
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .vocab-container {
        padding: 20px;
    }
    
    .current-word {
        font-size: 2rem;
    }
    
    .footer-content {
        flex-direction: column;
        text-align: center;
    }
}

/* Animation */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.feature-card {
    animation: fadeInUp 0.6s ease forwards;
}

.feature-card:nth-child(2) {
    animation-delay: 0.2s;
}

.feature-card:nth-child(3) {
    animation-delay: 0.4s;
}