body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #2c3e50, #34495e);
    color: #ecf0f1;
    line-height: 1.6;
    margin: 0;
    padding: 20px;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    background: rgba(255, 255, 255, 0.05);
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

h1 {
    text-align: center;
    color: #3498db;
    margin-bottom: 30px;
    font-size: 2.5rem;
}

h2 {
    color: #f1c40f;
    border-bottom: 2px solid #3498db;
    padding-bottom: 10px;
    margin-top: 30px;
}

h3 {
    color: #3498db;
    margin-top: 25px;
}

.instruction-section {
    margin-bottom: 25px;
    padding: 20px;
    background: rgba(0, 0, 0, 0.2);
    border-radius: 8px;
    border-left: 4px solid #3498db;
}

ul {
    padding-left: 20px;
}

li {
    margin-bottom: 8px;
}

.example-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
    max-width: 300px;
    margin: 20px auto;
}

.example-tile {
    background: linear-gradient(145deg, #3498db, #2980b9);
    color: white;
    padding: 15px;
    text-align: center;
    border-radius: 8px;
    font-weight: bold;
    font-size: 14px;
}

.example-tile.empty {
    background: rgba(255, 255, 255, 0.1);
    border: 2px dashed rgba(255, 255, 255, 0.3);
    color: rgba(255, 255, 255, 0.7);
}

.highlight {
    background: rgba(52, 152, 219, 0.2);
    padding: 2px 6px;
    border-radius: 4px;
    font-weight: bold;
}

.tip {
    background: rgba(241, 196, 15, 0.1);
    border-left: 4px solid #f1c40f;
    padding: 15px;
    margin: 15px 0;
    border-radius: 4px;
}

.back-btn {
    display: inline-block;
    background: linear-gradient(145deg, #3498db, #2980b9);
    color: white;
    padding: 12px 24px;
    text-decoration: none;
    border-radius: 8px;
    margin-top: 20px;
    transition: all 0.3s ease;
}

.back-btn:hover {
    background: linear-gradient(145deg, #5dade2, #3498db);
    transform: translateY(-2px);
}

.center-text {
    text-align: center;
}