* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: Arial, sans-serif;
}

body {
    background-color: #f0f2f5;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.container {
    background-color: white;
    border-radius: 10px;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
    padding: 2rem;
    width: 90%;
    max-width: 800px;
}

.screen {
    text-align: center;
}

.hidden {
    display: none;
}

h1 {
    color: #2c3e50;
    margin-bottom: 2rem;
}

h2 {
    color: #34495e;
    margin-bottom: 1.5rem;
}

.instructions {
    color: #7f8c8d;
    font-size: 1.1rem;
    margin-bottom: 2rem;
    line-height: 1.5;
}

.difficulty-selection {
    margin-bottom: 2rem;
}

.difficulty-info {
    display: flex;
    align-items: center;
    margin-bottom: 1rem;
    justify-content: center;
}

.difficulty-desc {
    color: #7f8c8d;
    margin-left: 1rem;
    font-size: 0.95rem;
}

.difficulty-btn {
    background-color: #3498db;
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    margin: 0.5rem;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s;
}

.difficulty-btn:hover {
    background-color: #2980b9;
}

.main-btn {
    background-color: #2ecc71;
    color: white;
    border: none;
    padding: 1rem 2rem;
    border-radius: 5px;
    cursor: pointer;
    font-size: 1.1rem;
    transition: background-color 0.3s;
}

.main-btn:hover {
    background-color: #27ae60;
}

.quit-btn {
    background-color: #e74c3c;
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: 5px;
    cursor: pointer;
    margin-left: 1rem;
    transition: background-color 0.3s;
}

.quit-btn:hover {
    background-color: #c0392b;
}

.home-btn {
    display: inline-block;
    background-color: #9b59b6;
    color: white;
    text-decoration: none;
    padding: 0.8rem 1.5rem;
    border-radius: 5px;
    margin-top: 1rem;
    transition: background-color 0.3s;
}

.home-btn:hover {
    background-color: #8e44ad;
}

.quiz-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: 2rem;
    color: #7f8c8d;
}

#question-text {
    font-size: 1.2rem;
    color: #2c3e50;
    margin-bottom: 1.5rem;
}

#options-container {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-bottom: 2rem;
}

.option-label {
    display: flex;
    align-items: center;
    padding: 1rem;
    border: 2px solid #bdc3c7;
    border-radius: 5px;
    cursor: pointer;
    transition: all 0.3s;
}

.option-label:hover {
    background-color: #f7f9fa;
}

.option-label input[type="radio"] {
    margin-right: 1rem;
}

#quiz-summary {
    margin-top: 2rem;
    text-align: left;
}

.summary-item {
    margin-bottom: 1rem;
    padding: 1rem;
    border-radius: 5px;
}

.correct {
    background-color: #d5f5e3;
    color: #27ae60;
}

.incorrect {
    background-color: #fadbd8;
    color: #c0392b;
}

#final-score {
    font-size: 1.5rem;
    color: #2c3e50;
    margin: 1rem 0;
}