/* Global Variables */
:root {
    --background: #f8f9fa;
    --surface: #ffffff;
    --text-primary: #212529;
    --text-secondary: #6c757d;
    --primary-accent: #0d6efd;
    --primary-accent-hover: #0b5ed7;
    --border-color: #dee2e6;
}

/* Global Reset */
body, h1, h2, h3, h4, h5, p, ul {
    margin: 0;
    padding: 0;
}

/* Base Styles */
body {
    font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background: var(--background);
    padding-top: 80px;
}

/* Header */
.main-header {
    background: var(--white);
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
    padding: 1rem 0;
    border-bottom: 1px solid var(--border-color);
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

.logo {
    display: flex;
    align-items: center;
}

.logo a {
    text-decoration: none;
}

.logo h1 {
    color: var(--text-primary);
    font-size: 2rem;
    margin-bottom: 0;
}

.logo .subtitle {
    font-size: 0.9rem;
    color: var(--text-secondary);
    max-width: 250px;
}

/* Navigation */
.main-nav ul {
    display: flex;
    gap: 2rem;
    list-style: none;
}

.main-nav a {
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 500;
    transition: color 0.3s;
}

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

/* Hero Section */
.hero {
    background: var(--surface);
    padding: 4rem 0;
    text-align: center;
    border-bottom: 1px solid var(--border-color);
}

.hero h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.hero p {
    max-width: 600px;
    margin: 0 auto 2rem;
    color: var(--text-secondary);
}

.buttons .btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: 50px;
    text-decoration: none;
    transition: background 0.3s;
    margin: 0 0.5rem;
}

.btn.primary {
    background: var(--primary-accent);
    color: var(--surface);
    border: 1px solid var(--primary-accent);
}

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

.btn.secondary {
    background: transparent;
    color: var(--primary-accent);
    border: 1px solid var(--primary-accent);
}

.btn.secondary:hover {
    background: var(--primary-accent);
    color: var(--surface);
}

/* Section Layout */
section {
    padding: 4rem 0;
}

.container {
    width: 90%;
    max-width: 1200px;
    margin: 0 auto;
}

/* Paper Sections */
.papers-list {
    display: grid;
    gap: 2rem;
}

.paper-card, .paper-item {
    background: var(--surface);
    padding: 1.5rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    transition: box-shadow 0.2s ease-in-out;
}

.paper-item:hover {
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}

.paper-item-content {
    flex-grow: 1;
}

.paper-item h3 {
    font-size: 1.2rem;
    margin-bottom: 0.5rem;
}

.paper-meta {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

.paper-keywords {
    margin-top: 1rem;
    margin-bottom: 1.5rem;
}

.paper-keywords .keyword {
    display: inline-block;
    background: #e9ecef;
    color: var(--text-secondary);
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    font-size: 0.8rem;
    margin-right: 0.5rem;
    margin-bottom: 0.5rem;
}

.paper-actions {
    display: flex;
    gap: 1rem;
    margin-top: auto;
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
}

.paper-actions .btn {
    padding: 0.5rem 1rem;
    font-size: 0.9rem;
}


/* Submission Process */
.submit-paper .submission-process .step {
    display: flex;
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.step-number {
    background: var(--primary-accent);
    color: var(--surface);
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    font-weight: bold;
}

/* Submission Tools Box */
.submit-paper .submission-tools {
    background: var(--surface);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
    margin-top: 2rem;
}

.submit-paper .submission-tools pre {
    background: #f9f9f9;
    padding: 1rem;
    border-radius: 4px;
    overflow-x: auto;
}

.copy-btn {
    display: inline-block;
    padding: 0.5rem 1rem;
    background: var(--primary-accent);
    color: var(--surface);
    border: none;
    border-radius: 4px;
    cursor: pointer;
    margin-top: 0.5rem;
    transition: background 0.3s;
}

.copy-btn:hover {
    background: var(--primary-accent-hover);
}

/* Filter Controls */
.filter-controls {
    margin-bottom: 2rem;
}

.filter-bar {
    display: flex;
    gap: 1rem;
    margin-bottom: 1rem;
}

#search-papers {
    flex-grow: 1;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 4px;
}

#sort-papers {
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 4px;
}

.category-filters {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.category-filters .btn {
    background: #e9ecef;
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
    padding: 0.5rem 1rem;
    cursor: pointer;
    border-radius: 20px;
    transition: all 0.2s ease;
}

.category-filters .btn:hover {
    background: #ced4da;
}

.category-filters .btn.active {
    background: var(--primary-accent);
    color: var(--surface);
    border-color: var(--primary-accent);
}


/* Citation Modal */
.modal {
    display: none;
    position: fixed;
    z-index: 2000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0,0,0,0.5);
}

.modal-content {
    background-color: var(--surface);
    margin: 15% auto;
    padding: 2rem;
    border: 1px solid #888;
    width: 80%;
    max-width: 600px;
    border-radius: 8px;
    position: relative;
}

.close-button {
    color: #aaa;
    position: absolute;
    top: 1rem;
    right: 1.5rem;
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
}

#bibtex-citation {
    background: var(--background);
    padding: 1rem;
    border-radius: 4px;
    white-space: pre-wrap;
    word-wrap: break-word;
    margin-bottom: 1rem;
    border: 1px solid var(--border-color);
}

/* Footer */
.main-footer {
    background: var(--text-primary);
    color: var(--background);
    padding: 4rem 0 2rem;
    text-align: center;
}

.main-footer p {
    margin-bottom: 1rem;
}

.social-links {
    list-style: none;
    display: inline-flex;
    gap: 1.5rem;
    padding: 0;
}

.social-links a {
    color: var(--surface);
    font-size: 1.5rem;
    transition: color 0.3s;
}

.social-links a:hover {
    color: var(--primary-accent);
}