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

body {
    font-family: 'Arial', sans-serif;
    line-height: 1.6;
    background-color: #0a0a1a;
    color: #e0e0e0;
}

header {
    background: linear-gradient(135deg, #1a1a3a, #2a2a5a);
    color: white;
    text-align: center;
    padding: 2rem 0;
    margin-bottom: 2rem;
    border-bottom: 3px solid #4a4a8a;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
    color: #00ff88;
    text-shadow: 0 0 10px rgba(0, 255, 136, 0.3);
}

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

.difficulty-section {
    margin-bottom: 3rem;
}

.difficulty-section h2 {
    color: #00ff88;
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid #4a4a8a;
}

.challenge-card {
    background: #1a1a3a;
    border-radius: 8px;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.3);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    border: 1px solid #4a4a8a;
}

.challenge-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 6px 12px rgba(0, 255, 136, 0.1);
}

.challenge-card h3 {
    color: #00ff88;
    margin-bottom: 1rem;
    font-size: 1.5rem;
}

.difficulty {
    display: inline-block;
    padding: 0.3rem 0.8rem;
    border-radius: 15px;
    font-size: 0.9rem;
    margin-bottom: 1rem;
    background-color: #2a2a5a;
    color: #00ff88;
    border: 1px solid #4a4a8a;
}

code {
    display: block;
    background-color: #0a0a2a;
    padding: 1rem;
    margin: 1rem 0;
    border-radius: 4px;
    font-family: 'Courier New', monospace;
    word-wrap: break-word;
    color: #00ff88;
    border: 1px solid #4a4a8a;
}

.hint {
    margin-top: 1rem;
    padding: 0.8rem;
    background-color: #2a2a5a;
    border-radius: 4px;
    font-style: italic;
    color: #aaa;
    border-left: 4px solid #00ff88;
}

.solve-btn {
    background-color: #1a237e;
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: 4px;
    cursor: pointer;
    font-size: 1rem;
    transition: background-color 0.2s ease;
}

.solve-btn:hover {
    background-color: #0d47a1;
}

.solution {
    display: none;
    margin-top: 1rem;
    padding: 1rem;
    background-color: #e8f5e9;
    border-radius: 4px;
    border-left: 4px solid #43a047;
}

.solution.show {
    display: block;
}

.solution ol {
    margin-left: 1.5rem;
    margin-top: 0.5rem;
}

.solution li {
    margin-bottom: 0.5rem;
}

footer {
    text-align: center;
    padding: 2rem;
    background-color: #1a1a3a;
    color: #888;
    margin-top: 3rem;
    border-top: 3px solid #4a4a8a;
}

footer p {
    margin: 0.5rem 0;
}

@media (max-width: 768px) {
    .challenges-container {
        padding: 0 15px;
    }
    
    header h1 {
        font-size: 2rem;
    }
    
    .challenge-card {
        padding: 1rem;
    }
}