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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f5f5;
}

header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    text-align: center;
    padding: 3rem 1rem;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

header p {
    font-size: 1.1rem;
    opacity: 0.9;
}

.container {
    display: grid;
    grid-template-columns: 1fr 300px;
    gap: 2rem;
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 1rem;
}

.posts {
    background: white;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

.posts h2 {
    color: #667eea;
    margin-bottom: 1.5rem;
    font-size: 1.5rem;
}

.post-list {
    list-style: none;
}

.post-list li {
    padding: 0.75rem 0;
    border-bottom: 1px solid #eee;
}

.post-list li:last-child {
    border-bottom: none;
}

.post-list a {
    color: #667eea;
    text-decoration: none;
    font-size: 1.1rem;
    transition: color 0.3s;
}

.post-list a:hover {
    color: #764ba2;
    text-decoration: underline;
}

.post {
    margin-bottom: 3rem;
    padding-bottom: 2rem;
    border-bottom: 1px solid #eee;
}

.post:last-child {
    border-bottom: none;
    margin-bottom: 0;
    padding-bottom: 0;
}

.post h2 {
    margin-bottom: 0.5rem;
    font-size: 1.8rem;
}

.post-title-link {
    color: #667eea;
    text-decoration: none;
    transition: color 0.3s;
}

.post-title-link:hover {
    color: #764ba2;
}

.post-date {
    color: #888;
    font-size: 0.9rem;
    margin-bottom: 1rem;
}

.post-image {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
    margin: 1rem 0 0.5rem 0;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.post-caption {
    font-size: 0.85rem;
    color: #888;
    margin: 0 0 1rem 0;
    font-style: italic;
    text-align: center;
}

.post-kousatu {
    font-size: 0.9rem;
    color: #003366;
    margin: 0.5rem 0 1rem 0;
    padding-left: 1rem;
    border-left: 3px solid #ddd;
    line-height: 1.5;
}

.post p {
    margin-bottom: 1rem;
}

.back-link {
    display: inline-block;
    margin-top: 1rem;
    color: #667eea;
    text-decoration: none;
    transition: color 0.3s;
    font-weight: 500;
}

.back-link:hover {
    color: #764ba2;
    text-decoration: underline;
}

.post-navigation {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    margin-top: 2rem;
    padding-top: 1.5rem;
    border-top: 1px solid #eee;
}

.post-navigation a {
    flex: 1;
    padding: 1rem;
    background-color: #f0f4ff;
    border-radius: 6px;
    color: #667eea;
    text-decoration: none;
    transition: all 0.3s;
    border: 1px solid #e0e7ff;
    text-align: center;
    font-weight: 500;
}

.post-navigation a:hover {
    background-color: #e0e7ff;
    border-color: #667eea;
    color: #764ba2;
}

.post-navigation .nav-prev {
    text-align: left;
}

.post-navigation .nav-next {
    text-align: right;
}

.post-navigation span {
    flex: 1;
}

.sidebar {
    background: white;
    padding: 1.5rem;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
    height: fit-content;
}

.sidebar h3 {
    color: #667eea;
    margin-top: 0;
    margin-bottom: 1rem;
    font-size: 1.2rem;
}

.sidebar p {
    font-size: 0.95rem;
    margin-bottom: 1.5rem;
    line-height: 1.5;
}

.sidebar ul {
    list-style: none;
}

.sidebar ul li {
    margin-bottom: 0.5rem;
}

.sidebar ul li a {
    color: #667eea;
    text-decoration: none;
    transition: color 0.3s;
}

.sidebar ul li a:hover {
    color: #764ba2;
    text-decoration: underline;
}

.progress-info {
    background-color: #f9f9f9;
    padding: 1rem;
    border-radius: 6px;
    border-left: 4px solid #667eea;
}

.progress-item {
    margin-bottom: 1rem;
}

.progress-item:last-child {
    margin-bottom: 0;
}

.progress-item strong {
    color: #667eea;
    display: block;
    margin-bottom: 0.3rem;
    font-size: 0.95rem;
}

.progress-item p {
    margin: 0;
    padding-left: 1rem;
    color: #555;
}

footer {
    background-color: #333;
    color: white;
    text-align: center;
    padding: 2rem 1rem;
    margin-top: 3rem;
    font-size: 0.9rem;
}

@media (max-width: 768px) {
    .container {
        grid-template-columns: 1fr;
    }

    header h1 {
        font-size: 1.8rem;
    }

    .posts {
        padding: 1rem;
    }

    .sidebar {
        padding: 1rem;
    }
}