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

body {
    font-family: 'Hiragino Sans', 'Hiragino Kaku Gothic ProN', 'Yu Gothic', 'Meiryo', sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f5f5;
}

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

header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 60px 20px;
    text-align: center;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 10px;
}

.subtitle {
    font-size: 1.2rem;
    opacity: 0.9;
}

main {
    padding: 40px 20px;
}

section {
    margin-bottom: 60px;
}

h2 {
    font-size: 2rem;
    margin-bottom: 30px;
    color: #667eea;
    text-align: center;
}

h3 {
    font-size: 1.5rem;
    margin-bottom: 15px;
    color: #333;
}

h4 {
    font-size: 1.2rem;
    margin-bottom: 10px;
}

.intro {
    background: white;
    padding: 40px;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    text-align: center;
}

.intro p {
    font-size: 1.1rem;
    line-height: 1.8;
}

.days-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.day-card {
    background: white;
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    text-align: center;
}

.day-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 5px 20px rgba(0,0,0,0.15);
}

.day-number {
    display: inline-block;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 8px 20px;
    border-radius: 20px;
    font-weight: bold;
    margin-bottom: 20px;
    font-size: 0.9rem;
}

.day-card h3 {
    margin-bottom: 15px;
    color: #667eea;
}

.day-card p {
    color: #666;
    margin-bottom: 20px;
    line-height: 1.6;
}

.btn {
    display: inline-block;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 12px 30px;
    text-decoration: none;
    border-radius: 25px;
    transition: opacity 0.3s ease;
    font-weight: bold;
}

.btn:hover {
    opacity: 0.9;
}

.features {
    background: white;
    padding: 40px;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin-top: 30px;
}

.feature-item {
    text-align: center;
    padding: 20px;
}

.feature-item h4 {
    font-size: 1.3rem;
    margin-bottom: 10px;
    color: #667eea;
}

.feature-item p {
    color: #666;
    line-height: 1.6;
}

.lesson-content {
    background: white;
    padding: 40px;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    margin-bottom: 30px;
}

.lesson-content h3 {
    color: #667eea;
    margin-top: 30px;
    margin-bottom: 15px;
    padding-bottom: 10px;
    border-bottom: 2px solid #f0f0f0;
}

.lesson-content ul, .lesson-content ol {
    margin-left: 25px;
    margin-bottom: 20px;
}

.lesson-content li {
    margin-bottom: 10px;
    line-height: 1.8;
}

.highlight-box {
    background: #f8f9ff;
    border-left: 4px solid #667eea;
    padding: 20px;
    margin: 20px 0;
    border-radius: 5px;
}

.highlight-box h4 {
    color: #667eea;
    margin-bottom: 10px;
}

.example-box {
    background: #fff9e6;
    border-left: 4px solid #ffc107;
    padding: 20px;
    margin: 20px 0;
    border-radius: 5px;
}

.example-box h4 {
    color: #f57c00;
    margin-bottom: 10px;
}

.navigation {
    display: flex;
    justify-content: space-between;
    margin-top: 40px;
    gap: 20px;
}

.nav-btn {
    display: inline-block;
    background: #667eea;
    color: white;
    padding: 12px 30px;
    text-decoration: none;
    border-radius: 5px;
    transition: background 0.3s ease;
}

.nav-btn:hover {
    background: #5568d3;
}

.nav-btn.prev::before {
    content: "← ";
}

.nav-btn.next::after {
    content: " →";
}

.breadcrumb {
    background: white;
    padding: 15px 20px;
    border-radius: 5px;
    margin-bottom: 20px;
    box-shadow: 0 1px 5px rgba(0,0,0,0.05);
}

.breadcrumb a {
    color: #667eea;
    text-decoration: none;
    margin-right: 5px;
}

.breadcrumb a:hover {
    text-decoration: underline;
}

.breadcrumb span {
    color: #999;
    margin: 0 5px;
}

footer {
    background: #333;
    color: white;
    text-align: center;
    padding: 30px 20px;
    margin-top: 60px;
}

@media (max-width: 768px) {
    header h1 {
        font-size: 2rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    h2 {
        font-size: 1.5rem;
    }

    .days-grid {
        grid-template-columns: 1fr;
    }

    .features-grid {
        grid-template-columns: 1fr;
    }

    .lesson-content {
        padding: 20px;
    }

    .navigation {
        flex-direction: column;
    }

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