/* Basic CSS Starter - Customize as needed */

/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: #333;
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

/* Header */
header {
    text-align: center;
    padding: 40px 20px;
    border-bottom: 2px solid #eee;
    margin-bottom: 30px;
}

header h1 {
    font-size: 2.5em;
    margin-bottom: 10px;
    color: #2c3e50;
}

header p {
    font-size: 1.1em;
    color: #7f8c8d;
    margin: 5px 0;
}

/* Navigation */
nav {
    margin-bottom: 40px;
}

nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 20px;
    padding: 20px 0;
    background: #f8f9fa;
    border-radius: 8px;
}

nav ul li a {
    text-decoration: none;
    color: #2c3e50;
    font-weight: 500;
    padding: 8px 16px;
    border-radius: 4px;
    transition: background 0.3s;
}

nav ul li a:hover,
nav ul li a.active {
    background: #3498db;
    color: white;
}

/* Main Content */
main {
    margin-bottom: 60px;
}

section {
    margin-bottom: 40px;
}

h2 {
    color: #2c3e50;
    font-size: 1.8em;
    margin-bottom: 15px;
    border-bottom: 2px solid #3498db;
    padding-bottom: 10px;
}

.paper-container {
    display: flex;
    gap: 30px;
    align-items: flex-start;
}

.paper-list {
    flex: 1 1 260px;
    background: #f8f9fa;
    padding: 20px;
    border-radius: 10px;
    border: 1px solid #e0e6ed;
    position: sticky;
    top: 30px;
    max-height: calc(100vh - 120px);
    overflow-y: auto;
}

.paper-list h2 {
    border-bottom: none;
    font-size: 1.4em;
    margin-bottom: 15px;
}

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

.paper-list li {
    margin-bottom: 15px;
}

.paper-list a {
    font-weight: 600;
    color: #2c3e50;
}

.paper-list a.active {
    color: #3498db;
}

.paper-list__description {
    font-size: 0.9em;
    color: #6c7a89;
    margin-top: 4px;
}

.paper-detail {
    flex: 2 1 520px;
}

.paper-empty {
    background: #f5f7fa;
    border: 1px dashed #b8c3d0;
    padding: 40px;
    border-radius: 12px;
    text-align: center;
}

.paper-intro {
    background: #eef6ff;
    border-left: 4px solid #3498db;
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 25px;
}

.paper-accordion {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.paper-question {
    border: 1px solid #d7e1ec;
    border-radius: 10px;
    background: #fff;
    overflow: hidden;
    box-shadow: 0 6px 18px rgba(52, 152, 219, 0.08);
}

.paper-question summary {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 15px;
    padding: 18px 22px;
    cursor: pointer;
    font-weight: 600;
    color: #2c3e50;
    list-style: none;
}

.paper-question summary::-webkit-details-marker {
    display: none;
}

.paper-question__icon {
    background: #3498db;
    color: #fff;
    width: 28px;
    height: 28px;
    border-radius: 50%;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2em;
    transition: transform 0.3s ease;
}

.paper-question[open] .paper-question__icon {
    transform: rotate(180deg);
}

.paper-question__content {
    padding: 0 22px 22px;
    border-top: 1px solid #e6edf5;
}

.paper-question__content pre {
    background: #f8f9fa;
    color: #2c3e50;
    padding: 16px;
    border-radius: 8px;
    overflow-x: auto;
    font-family: 'Courier New', Consolas, Monaco, 'Lucida Console', monospace;
    font-size: 0.9em;
    line-height: 1.5;
    border: 1px solid #d7e1ec;
    margin: 15px 0;
    white-space: pre-wrap;
    word-wrap: break-word;
}

.paper-question__content pre code {
    background: transparent;
    padding: 0;
    color: inherit;
    font-size: inherit;
    line-height: inherit;
    display: block;
}

.paper-question__content code {
    background: #e8f4f8;
    padding: 2px 6px;
    border-radius: 4px;
    font-family: 'Courier New', Consolas, Monaco, monospace;
    color: #2c3e50;
}

.paper-question__content table {
    width: 100%;
    border-collapse: collapse;
    margin: 15px 0;
    font-size: 0.95em;
}

.paper-question__content table th,
.paper-question__content table td {
    border: 1px solid #d7e1ec;
    padding: 10px 12px;
    text-align: left;
}

.paper-question__content table th {
    background: #eef6ff;
    font-weight: 600;
    color: #2c3e50;
}

.paper-question__content table tr:nth-child(even) {
    background: #f8f9fa;
}

.paper-question__content table tr:hover {
    background: #eef6ff;
}

h3 {
    color: #34495e;
    font-size: 1.4em;
    margin: 20px 0 10px;
}

p {
    margin-bottom: 15px;
}

ul {
    margin-left: 20px;
    margin-bottom: 15px;
}

li {
    margin-bottom: 10px;
}

a {
    color: #3498db;
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

/* Forms */
form {
    max-width: 600px;
}

label {
    display: block;
    font-weight: 500;
    margin-bottom: 5px;
    color: #2c3e50;
}

input[type="text"],
input[type="email"],
textarea {
    width: 100%;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 1em;
    font-family: inherit;
}

textarea {
    resize: vertical;
}

button[type="submit"] {
    background: #3498db;
    color: white;
    padding: 12px 30px;
    border: none;
    border-radius: 4px;
    font-size: 1em;
    cursor: pointer;
    transition: background 0.3s;
}

button[type="submit"]:hover {
    background: #2980b9;
}

/* Messages */
.success-message {
    background: #d4edda;
    border: 1px solid #c3e6cb;
    color: #155724;
    padding: 15px;
    border-radius: 4px;
    margin-bottom: 20px;
}

.error-message {
    background: #f8d7da;
    border: 1px solid #f5c6cb;
    color: #721c24;
    padding: 15px;
    border-radius: 4px;
    margin-bottom: 20px;
}

/* Footer */
footer {
    text-align: center;
    padding: 30px 20px;
    border-top: 2px solid #eee;
    color: #7f8c8d;
    margin-top: 60px;
}

footer p {
    margin: 5px 0;
}

/* Responsive Design */
@media (max-width: 768px) {
    body {
        padding: 10px;
    }
    
    header h1 {
        font-size: 2em;
    }
    
    nav ul {
        flex-direction: column;
        align-items: center;
    }
    
    h2 {
        font-size: 1.5em;
    }

    .paper-container {
        flex-direction: column;
    }

    .paper-list {
        position: static;
        max-height: none;
    }
}

/* Video Placeholders */
.video-placeholder {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 20px;
    border-left: 4px solid #3498db;
}

.video-placeholder h3 {
    margin-top: 0;
}

.video-placeholder .status {
    color: #7f8c8d;
    font-style: italic;
}

/* Play Button */
.play-button {
    display: inline-block;
    background: #e74c3c;
    color: white;
    padding: 12px 24px;
    border-radius: 4px;
    font-weight: 500;
    text-decoration: none;
    transition: background 0.3s;
}

.play-button:hover {
    background: #c0392b;
    text-decoration: none;
}