:root {
    --background: #E0E5EC;
    --text-color: #333;
    --glass-bg: rgba(255, 255, 255, 0.4);
    --glass-border: rgba(0, 0, 0, 0.1);
    --hover-bg: rgba(255, 255, 255, 0.6);
}
body {
    font-family: 'Montserrat', sans-serif;
    margin: 0;
    background-color: var(--background);
    color: var(--text-color);
    padding: 20px;
    box-sizing: border-box;
}
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    width: 100%;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}
h1 {
    font-size: 2em;
    font-weight: 600;
}
.back-button {
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    color: var(--text-color);
    font-family: inherit;
    padding: 10px 20px;
    border-radius: 50px;
    cursor: pointer;
    font-size: 1em;
    font-weight: 600;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 1.2px;
    text-decoration: none;
}
.back-button:hover {
    background: var(--hover-bg);
    transform: translateY(-2px);
}
.search-container {
    margin-bottom: 40px;
    width: 100%;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}
#search-bar {
    width: 100%;
    padding: 12px 20px;
    border-radius: 50px;
    border: 1px solid var(--glass-border);
    font-size: 1em;
    background-color: var(--glass-bg);
    box-sizing: border-box;
    font-family: 'Montserrat', sans-serif;
}
.content {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 20px;
    width: 100%;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}
.paper-card {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
    border-radius: 30px;
    padding: 20px;
    transition: all 0.3s ease;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: space-between;
    text-align: center;
    aspect-ratio: 1 / 1;
    text-decoration: none;
}
.paper-card:hover {
    transform: translateY(-5px);
}
.paper-title {
    font-weight: 600;
    color: var(--text-color);
    font-size: 1.0em;
}
.download-buttons {
    display: flex;
    flex-direction: column;
    gap: 10px;
    width: 100%;
}
.download-btn {
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    color: var(--text-color);
    text-decoration: none;
    padding: 8px 12px;
    border-radius: 50px;
    font-size: 0.9em;
    transition: all 0.3s ease;
    display: block;
}
.download-btn:hover {
    background: var(--hover-bg);
    transform: translateY(-2px);
}

footer {
    margin-top: 30px;
    text-align: center;
    font-size: 0.9em;
    padding: 10px;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

footer a {
    color: var(--text-color);
    text-decoration: none;
    margin: 0 10px;
    white-space: nowrap;
}

#scrollToTopBtn {
    display: none;
    position: fixed;
    bottom: 20px;
    right: 20px;
    z-index: 99;
    border: none;
    outline: none;
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    color: var(--text-color);
    cursor: pointer;
    padding: 10px;
    border-radius: 50%;
    font-size: 20px;
    width: 50px;
    height: 50px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    transition: all 0.3s ease;
    border: 1px solid var(--glass-border);
    justify-content: center;
    align-items: center;
}

#scrollToTopBtn:hover {
    background: var(--hover-bg);
    transform: translateY(-5px);
}