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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: #f8f9fa;
    color: #222;
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    background-color: white;
    min-height: 100vh;
}

/* Header */
.header {
    border-bottom: 1px solid #a2a9b1;
    padding: 10px 20px;
    background-color: #f8f9fa;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 10px;
}

.logo img {
    width: 40px;
    height: 40px;
}

.site-name {
    font-size: 24px;
    font-weight: normal;
}

.nav-tabs {
    display: flex;
    gap: 20px;
    margin-bottom: 10px;
    font-size: 13px;
}

.nav-tabs a {
    color: #0645ad;
    text-decoration: none;
    padding: 5px 10px;
    border: 1px solid transparent;
}

.nav-tabs a:hover {
    text-decoration: underline;
}

.nav-tabs a.active {
    color: #000;
    border: 1px solid #a2a9b1;
    border-bottom: 1px solid white;
    background-color: white;
}

.search-box {
    display: flex;
    gap: 5px;
    margin-bottom: 10px;
}

.search-box input {
    flex: 1;
    max-width: 300px;
    padding: 5px;
    border: 1px solid #a2a9b1;
}

.search-box button {
    padding: 5px 15px;
    background-color: #f8f9fa;
    border: 1px solid #a2a9b1;
    cursor: pointer;
}

/* Main Content */
.main-content {
    display: flex;
    min-height: calc(100vh - 200px);
}

/* Sidebar */
.sidebar {
    width: 176px;
    padding: 20px 10px;
    background-color: #f6f6f6;
    border-right: 1px solid #a2a9b1;
}

.sidebar-section {
    margin-bottom: 20px;
}

.sidebar-section h3 {
    font-size: 12px;
    font-weight: normal;
    color: #4d5156;
    margin-bottom: 5px;
    padding: 5px;
    background-color: #ddd;
}

.sidebar-section ul {
    list-style: none;
}

.sidebar-section li {
    padding: 2px 5px;
}

.sidebar-section a {
    color: #0645ad;
    text-decoration: none;
    font-size: 13px;
}

.sidebar-section a:hover {
    text-decoration: underline;
}

/* Article */
.article {
    flex: 1;
    padding: 20px;
}

.article h1 {
    font-size: 32px;
    font-weight: normal;
    border-bottom: 1px solid #a2a9b1;
    padding-bottom: 10px;
    margin-bottom: 20px;
}

.article h2 {
    font-size: 24px;
    font-weight: normal;
    border-bottom: 1px solid #a2a9b1;
    margin-top: 30px;
    margin-bottom: 15px;
    padding-bottom: 5px;
}

.article h3 {
    font-size: 18px;
    font-weight: bold;
    margin-top: 20px;
    margin-bottom: 10px;
}

.article p {
    margin-bottom: 15px;
    text-align: justify;
}

.article a {
    color: #0645ad;
    text-decoration: none;
}

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

.article ul, .article ol {
    margin-left: 40px;
    margin-bottom: 15px;
}

/* Info Box */
.info-box {
    float: right;
    width: 300px;
    margin: 0 0 20px 20px;
    border: 1px solid #a2a9b1;
    background-color: #f8f9fa;
    padding: 5px;
}

.info-box h4 {
    text-align: center;
    background-color: #ddd;
    padding: 5px;
    margin-bottom: 10px;
    font-weight: bold;
}

.info-box img {
    width: 100%;
    height: auto;
    margin-bottom: 10px;
}

.info-box table {
    width: 100%;
    font-size: 13px;
}

.info-box td {
    padding: 3px 5px;
    vertical-align: top;
}

.info-box td:first-child {
    font-weight: bold;
    width: 30%;
}

/* Table of Contents */
.toc {
    display: inline-block;
    border: 1px solid #a2a9b1;
    background-color: #f8f9fa;
    padding: 10px;
    margin-bottom: 20px;
}

.toc h2 {
    font-size: 16px;
    border: none;
    margin: 0 0 10px 0;
    padding: 0;
}

.toc ol {
    margin-left: 20px;
}

.toc a {
    color: #0645ad;
    text-decoration: none;
}

/* Equation */
.equation {
    background-color: #f8f9fa;
    padding: 15px;
    margin: 15px 0;
    text-align: center;
    font-family: "Times New Roman", serif;
    font-size: 18px;
    border: 1px solid #ddd;
}

/* Categories */
.categories {
    margin-top: 40px;
    padding-top: 20px;
    border-top: 1px solid #a2a9b1;
    font-size: 13px;
}

/* Footer */
.footer {
    background-color: #f8f9fa;
    border-top: 1px solid #a2a9b1;
    padding: 20px;
    font-size: 12px;
    color: #666;
}

.footer a {
    color: #0645ad;
    text-decoration: none;
}

/* Mobile Responsive */
@media (max-width: 768px) {
    .main-content {
        flex-direction: column;
    }
    
    .sidebar {
        width: 100%;
        border-right: none;
        border-bottom: 1px solid #a2a9b1;
    }
    
    .info-box {
        float: none;
        width: 100%;
        margin: 0 0 20px 0;
    }
    
    .search-box {
        flex-direction: column;
    }
    
    .search-box input {
        max-width: 100%;
    }
    
    .nav-tabs {
        flex-wrap: wrap;
    }
}