/* General Styles */
body {
    font-family: Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    margin: 0;
    padding: 0;
    background-color: #fff;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 15px;
}

a {
    color: #0000EE;
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

hr {
    border: none;
    border-top: 1px solid #ccc;
    margin: 20px 0;
}

/* Header Styles */
header {
    border-bottom: 1px solid #ccc;
    margin-bottom: 20px;
    padding: 10px 0;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

h1 {
    font-size: 28px;
    margin: 0;
}

.auth-links {
    font-size: 14px;
}

/* Main Content Styles */
main {
    min-height: 500px;
}

#intro {
    margin-bottom: 30px;
}

/* Category Styles */
.category {
    margin-bottom: 30px;
}

.category h2 {
    color: #333;
    border-bottom: 1px solid #eee;
    padding-bottom: 5px;
    margin-bottom: 10px;
}

.category ul {
    list-style-type: none;
    padding: 0;
    margin: 0;
}

.category li {
    margin-bottom: 8px;
}

/* Problem Content Styles */
#problem-content {
    padding: 20px;
    background-color: #f9f9f9;
    border: 1px solid #ddd;
    border-radius: 4px;
    margin-bottom: 30px;
}

.problem-header {
    margin-bottom: 20px;
}

.problem-header h2 {
    margin-bottom: 5px;
}

.problem-header p {
    color: #666;
    font-style: italic;
    margin-top: 0;
}

.problem-section {
    margin-bottom: 30px;
}

.problem-section h3 {
    border-bottom: 1px solid #eee;
    padding-bottom: 5px;
}

.problem-item {
    margin-bottom: 25px;
    padding-bottom: 15px;
    border-bottom: 1px dotted #ddd;
}

.problem-item:last-child {
    border-bottom: none;
}

.problem-item h4 {
    margin-bottom: 10px;
}

.problem-statement {
    margin-bottom: 15px;
}

.lean4-formalization {
    background-color: #f0f0f0;
    padding: 15px;
    border-left: 3px solid #0066cc;
    font-family: 'Courier New', monospace;
    margin-top: 10px;
    overflow-x: auto;
}

.remark {
    font-style: italic;
    color: #555;
    margin-top: 10px;
    padding-left: 15px;
    border-left: 2px solid #ccc;
}

/* Navigation */
.back-link {
    display: inline-block;
    margin-bottom: 20px;
    color: #0066cc;
}

/* Utility Classes */
.hidden {
    display: none;
}

/* Footer Styles */
footer {
    margin-top: 40px;
    padding: 20px 0;
    border-top: 1px solid #eee;
    font-size: 14px;
    color: #666;
}

/* Responsive Styles */
@media (max-width: 768px) {
    .header-content {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .auth-links {
        margin-top: 10px;
    }
    
    .category {
        margin-bottom: 20px;
    }
}