:root {
    --primary-color: #2c3e50;
    /* ダークネイビー */
    --secondary-color: #27ae60;
    /* 探偵のイメージのグリーン */
    --accent-color: #e67e22;
    /* アクセントのオレンジ */
    --bg-color: #ecf0f1;
    --text-color: #2c3e50;
    --card-bg: #ffffff;
}

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

body {
    font-family: 'Zen Maru Gothic', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    background-image:
        radial-gradient(var(--primary-color) 0.5px, transparent 0.5px);
    background-size: 30px 30px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.container {
    max-width: 800px;
    margin: 40px auto;
    padding: 20px;
    width: 100%;
}

.screen {
    display: none;
    background: var(--card-bg);
    padding: 50px;
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
    text-align: center;
    border: 4px solid var(--primary-color);
}

.screen.active {
    display: block;
    animation: fadeIn 0.4s ease-out;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

h1 {
    color: var(--primary-color);
    font-size: 2.8rem;
    margin-bottom: 25px;
}

.btn {
    display: inline-block;
    padding: 18px 50px;
    font-size: 1.3rem;
    font-weight: bold;
    color: white;
    background-color: var(--primary-color);
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s;
    margin: 15px;
}

.btn:hover {
    background-color: #34495e;
    transform: translateY(-2px);
}

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

.btn.next:hover {
    background-color: #2ecc71;
}

.quiz-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: 30px;
    font-size: 1.3rem;
    color: #555;
    border-bottom: 2px solid #eee;
    padding-bottom: 10px;
}

.question-box {
    background: #f8f9fa;
    padding: 40px;
    border-radius: 10px;
    margin-bottom: 30px;
    font-size: 1.8rem;
    color: #000;
    box-shadow: inset 0 2px 5px rgba(0, 0, 0, 0.05);
}

.choices-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
}

.choice-btn {
    padding: 20px;
    font-size: 1.3rem;
    background: white;
    border: 2px solid #ddd;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.2s;
}

.choice-btn:hover {
    border-color: var(--primary-color);
    background: #f0f3f6;
}

.choice-btn.correct {
    background-color: #d4edda;
    border-color: #28a745;
    color: #155724;
}

.choice-btn.incorrect {
    background-color: #f8d7da;
    border-color: #dc3545;
    color: #721c24;
}

.feedback-area {
    margin-top: 30px;
    padding: 25px;
    border-radius: 10px;
    background: #fff;
    border: 3px solid var(--accent-color);
    text-align: left;
}

.progress-bar-container {
    width: 100%;
    height: 12px;
    background: #dfe6e9;
    border-radius: 6px;
    margin-bottom: 30px;
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    width: 0%;
    transition: width 0.4s;
}

.back-link {
    display: block;
    margin-top: 25px;
    color: #7f8c8d;
    text-decoration: none;
    font-size: 1rem;
}

footer {
    text-align: center;
    padding: 30px;
    color: #95a5a6;
}