:root {
    --primary-color: #667eea;
    --secondary-color: #764ba2;
    --accent-color: #48bb78;
    --bg-light: #f7fafc;
    --bg-card: #ffffff;
    --text-primary: #2d3748;
    --text-secondary: #718096;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);
}

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

body {
    font-family: "Courier New", Courier, monospace;
    line-height: 1.6;
    color: var(--text-primary);
    background: var(--bg-light);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

header {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 2rem 1rem;
    text-align: center;
    box-shadow: var(--shadow-md);
}

header h1 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
    font-weight: 700;
}

header p {
    opacity: 0.9;
    font-size: 0.95rem;
}

nav {
    text-align: center;
    padding: 1rem;
    background: white;
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 100;
}

nav a {
    margin: 0 15px;
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 500;
    transition: color 0.3s ease;
    position: relative;
}

nav a:hover {
    color: var(--primary-color);
}

nav a::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: width 0.3s ease;
}

nav a:hover::after {
    width: 100%;
}

main {
    flex: 1;
    max-width: 900px;
    width: 100%;
    margin: 2rem auto;
    padding: 0 1.5rem;
}

/* Card Styles */
.card-container {
    display: grid;
    gap: 1.5rem;
    margin-top: 1.5rem;
}

.card {
    background: var(--bg-card);
    border-radius: 8px;
    padding: 1.5rem;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
    cursor: pointer;
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1rem;
    gap: 1rem;
}

.card-title {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    flex: 1;
}

.card-title a {
    color: var(--text-primary);
    text-decoration: none;
    transition: color 0.3s ease;
}

.card-title a:hover {
    color: var(--primary-color);
}

.external-link::after {
    content: " ↗";
    font-size: 0.8em;
    color: var(--accent-color);
}

.card-meta {
    display: flex;
    gap: 1rem;
    align-items: center;
    flex-wrap: wrap;
    margin-bottom: 0.75rem;
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.card-date {
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.card-summary {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.5;
    margin-bottom: 1rem;
}

.tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 1rem;
}

.tag {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: linear-gradient(135deg, #667eea15 0%, #764ba215 100%);
    color: var(--primary-color);
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 500;
    border: 1px solid var(--primary-color);
    transition: all 0.3s ease;
}

.tag:hover {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    transform: scale(1.05);
}

.tag.blog {
    background: linear-gradient(135deg, #48bb7815 0%, #38a16915 100%);
    color: var(--accent-color);
    border-color: var(--accent-color);
}

.tag.blog:hover {
    background: var(--accent-color);
    color: white;
}

/* Home Section */
#home {
    background: var(--bg-card);
    border-radius: 8px;
    padding: 2rem;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
}

#home h2 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-size: 1.5rem;
}

#home p {
    margin-bottom: 1rem;
    color: var(--text-secondary);
}

#home ul {
    list-style: none;
    padding-left: 1rem;
}

#home ul li {
    margin-bottom: 0.5rem;
    color: var(--text-secondary);
}

#home ul li::before {
    content: "▸ ";
    color: var(--primary-color);
    font-weight: bold;
    margin-right: 0.5rem;
}

/* Section Headers */
h2 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-size: 1.75rem;
    font-weight: 600;
}

/* Simple List Fallback */
ul {
    list-style: none;
}

ul li {
    margin-bottom: 0.75rem;
}

ul li a {
    color: var(--text-primary);
    text-decoration: none;
    transition: color 0.3s ease;
}

ul li a:hover {
    color: var(--primary-color);
}

/* Footer */
footer {
    text-align: center;
    padding: 2rem 1rem;
    background: white;
    color: var(--text-secondary);
    margin-top: auto;
    border-top: 1px solid var(--border-color);
}

/* Content Area for Paper Pages */
.content {
    max-width: 800px;
    margin: 20px auto;
    padding: 20px;
    background: var(--bg-card);
    border-radius: 8px;
    box-shadow: var(--shadow-sm);
}

.content code,
.content pre,
.content table {
    text-align: left;
}

.content img {
    border-radius: 8px;
    box-shadow: var(--shadow-md);
    margin: 1rem 0;
}

/* Responsive Design */
@media (max-width: 768px) {
    header h1 {
        font-size: 1.5rem;
    }
    
    nav a {
        margin: 0 8px;
        font-size: 0.9rem;
    }
    
    main {
        padding: 0 1rem;
    }
    
    .card {
        padding: 1rem;
    }
    
    .card-header {
        flex-direction: column;
    }
    
    .card-meta {
        font-size: 0.8rem;
    }
    
    .controls {
        flex-direction: column;
    }
    
    .search-box {
        width: 100%;
    }
}

/* Search and Sort Controls */
.controls {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
    align-items: center;
    flex-wrap: wrap;
}

.search-box {
    flex: 1;
    min-width: 250px;
}

.search-box input {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-family: "Courier New", Courier, monospace;
    font-size: 0.95rem;
    transition: all 0.3s ease;
    background: var(--bg-card);
}

.search-box input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.sort-buttons {
    display: flex;
    gap: 0.5rem;
}

.sort-btn {
    padding: 0.75rem 1.25rem;
    border: 2px solid var(--border-color);
    background: var(--bg-card);
    color: var(--text-primary);
    border-radius: 8px;
    font-family: "Courier New", Courier, monospace;
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
}

.sort-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.sort-btn.active {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    border-color: var(--primary-color);
}

/* Comment Section */
.comments-section {
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 2px solid var(--border-color);
}

.comments-section h3 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    font-size: 1.3rem;
}

.comment-form {
    background: var(--bg-card);
    padding: 1.5rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    margin-bottom: 2rem;
}

.comment-form input,
.comment-form textarea {
    width: 100%;
    padding: 0.75rem;
    margin-bottom: 1rem;
    border: 2px solid var(--border-color);
    border-radius: 6px;
    font-family: "Courier New", Courier, monospace;
    font-size: 0.9rem;
    transition: border-color 0.3s ease;
}

.comment-form input:focus,
.comment-form textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}

.comment-form textarea {
    min-height: 100px;
    resize: vertical;
}

.comment-form button {
    padding: 0.75rem 1.5rem;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    border: none;
    border-radius: 6px;
    font-family: "Courier New", Courier, monospace;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.comment-form button:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.comments-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.comment {
    background: var(--bg-card);
    padding: 1.25rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    transition: box-shadow 0.3s ease;
}

.comment:hover {
    box-shadow: var(--shadow-sm);
}

.comment-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.75rem;
}

.comment-author {
    font-weight: 600;
    color: var(--primary-color);
}

.comment-date {
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.comment-text {
    color: var(--text-primary);
    line-height: 1.6;
    margin-bottom: 0.5rem;
}

.comment-delete {
    padding: 0.4rem 0.8rem;
    background: transparent;
    color: #e53e3e;
    border: 1px solid #e53e3e;
    border-radius: 4px;
    font-family: "Courier New", Courier, monospace;
    font-size: 0.8rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.comment-delete:hover {
    background: #e53e3e;
    color: white;
}

.no-comments {
    text-align: center;
    padding: 2rem;
    color: var(--text-secondary);
    font-style: italic;
}

/* Hidden sections */
.blog-section,
.blog-post,
.paper-summary-section {
    display: none;
}