:root {
    /* Light theme variables */
    --bg-color: #F7F7F7;
    --text-color: #333;
    --footer-bg: #F7F7F7;
    --footer-border: #ddd;
    --header-bg: #D00000;
    --header-text-color: white;
    --link-color: #D00000;
    --link-hover-color: #A60000;
    --card-bg: #ffffff;
    --card-border: #eaeaea;
    --nav-bg: #ffffff;
    --nav-hover: #f0f0f0;
    --nav-active: #D00000;
    --nav-text: #333;
    --spinner-color: #D00000;
}

[data-theme="dark"] {
    --bg-color: #1a1a1a;
    --text-color: #e0e0e0;
    --footer-bg: #1a1a1a;
    --footer-border: #333;
    --header-bg: #8B0000;
    --header-text-color: #ffffff;
    --link-color: #ff4444;
    --link-hover-color: #ff6666;
    --card-bg: #2a2a2a;
    --card-border: #333;
    --nav-bg: #2a2a2a;
    --nav-hover: #333;
    --nav-active: #ff4444;
    --nav-text: #e0e0e0;
    --spinner-color: #ff4444;
}

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

body {
    font-family: 'Arial', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

/* Theme toggle */
.theme-toggle {
    position: fixed;
    top: 1rem;
    right: 1rem;
    z-index: 1000;
}

.theme-toggle button {
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 50%;
    background-color: var(--card-bg);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.theme-toggle svg {
    width: 24px;
    height: 24px;
    fill: var(--text-color);
}

.sun-icon {
    display: none;
}

[data-theme="dark"] .moon-icon {
    display: none;
}

[data-theme="dark"] .sun-icon {
    display: block;
}

/* Header */
header {
    background-color: var(--header-bg);
    color: var(--header-text-color);
    padding: 2rem 1rem;
    text-align: center;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

header h1 {
    font-size: 2rem;
    font-weight: bold;
}

/* Container layout */
.container {
    display: flex;
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 1rem;
    gap: 2rem;
}

/* Year navigation */
.year-nav {
    flex: 0 0 200px;
    position: sticky;
    top: 2rem;
    height: fit-content;
    background-color: var(--nav-bg);
    border-radius: 8px;
    padding: 1rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.search-container {
    position: relative;
    margin-bottom: 1rem;
}

#searchInput {
    width: 100%;
    padding: 0.75rem;
    padding-right: 2rem;
    border: 1px solid var(--card-border);
    border-radius: 4px;
    background-color: var(--card-bg);
    color: var(--text-color);
    font-size: 0.95rem;
    transition: border-color 0.2s, box-shadow 0.2s;
}

#searchInput:focus {
    outline: none;
    border-color: var(--header-bg);
    box-shadow: 0 0 0 2px rgba(208, 0, 0, 0.1);
}

.search-clear {
    position: absolute;
    right: 0.75rem;
    top: 50%;
    transform: translateY(-50%);
    cursor: pointer;
    color: var(--text-color);
    font-size: 1.2rem;
    opacity: 0.6;
    transition: opacity 0.2s;
}

.search-clear:hover {
    opacity: 1;
}

.year-nav nav {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.year-nav button {
    background: none;
    border: none;
    padding: 0.5rem 1rem;
    text-align: left;
    color: var(--nav-text);
    cursor: pointer;
    border-radius: 4px;
    transition: background-color 0.2s;
}

.year-nav button:hover {
    background-color: var(--nav-hover);
}

.year-nav button.active {
    background-color: var(--nav-active);
    color: white;
}

/* Main content */
main {
    flex: 1;
    min-width: 0;
}

/* Publication cards */
.publication {
    background-color: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 8px;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    transition: transform 0.2s, box-shadow 0.2s;
}

.publication:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.15);
}

.publication h2 {
    font-size: 1.25rem;
    margin-bottom: 1rem;
}

.publication p {
    margin-bottom: 0.5rem;
}

.publication a {
    color: var(--link-color);
    text-decoration: none;
    transition: color 0.2s;
}

.publication a:hover {
    color: var(--link-hover-color);
    text-decoration: underline;
}

/* Year sections */
.year-section {
    margin-bottom: 2rem;
}

.year-section h2 {
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
    padding: 0.75rem 1rem;
    background-color: var(--card-bg);
    border-bottom: 2px solid var(--header-bg);
    position: sticky;
    top: 0;
    z-index: 10;
    backdrop-filter: blur(8px);
    transition: background-color 0.3s;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

/* Loading spinner */
.loading {
    text-align: center;
    padding: 2rem;
}

.loading-spinner {
    width: 40px;
    height: 40px;
    border: 4px solid rgba(0, 0, 0, 0.1);
    border-left-color: var(--spinner-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 1rem;
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

/* Error state */
.error {
    text-align: center;
    padding: 2rem;
    background-color: var(--card-bg);
    border-radius: 8px;
    border: 1px solid var(--card-border);
}

.error button {
    margin-top: 1rem;
    padding: 0.5rem 1rem;
    background-color: var(--header-bg);
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    transition: background-color 0.2s;
}

.error button:hover {
    background-color: var(--link-hover-color);
}

/* Footer */
footer {
    background-color: var(--footer-bg);
    color: var(--text-color);
    padding: 1.5rem;
    text-align: center;
    border-top: 1px solid var(--footer-border);
    margin-top: 2rem;
}

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

/* Responsive design */
@media (max-width: 768px) {
    .container {
        flex-direction: column;
    }

    .year-nav {
        position: static;
        width: 100%;
    }

    .year-nav nav {
        flex-direction: row;
        flex-wrap: wrap;
        gap: 0.5rem;
    }

    .year-nav button {
        flex: 1;
        min-width: max-content;
        text-align: center;
    }
}

/* Page Navigation */
.page-navigation {
    display: flex;
    justify-content: center;
    margin: 1rem 0;
    gap: 1rem;
    background-color: var(--nav-bg);
    padding: 0.5rem;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.page-navigation .nav-button {
    padding: 0.5rem 1rem;
    color: var(--nav-text);
    text-decoration: none;
    border-radius: 4px;
    background-color: transparent;
    border: 1px solid var(--card-border);
    transition: background-color 0.3s, color 0.3s, transform 0.2s;
    font-weight: bold;
    text-align: center;
}

.page-navigation .nav-button:hover {
    background-color: var(--nav-hover);
    transform: translateY(-2px);
}

.page-navigation .nav-button.active {
    background-color: var(--nav-active);
    color: white;
    border-color: var(--nav-active);
}