body {
    font-family: Arial, sans-serif;
    background-color: #f4f7f9;
    color: #333;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
}

.container {
    background-color: #fff;
    padding: 2em;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    width: 90%;
    max-width: 1200px;
    box-sizing: border-box;
}

h1 {
    text-align: center;
    color: #0056b3;
}

.upload-area {
    border: 2px dashed #ccc;
    border-radius: 8px;
    padding: 2em;
    text-align: center;
    cursor: pointer;
    transition: border-color 0.3s ease;
}

.upload-area.drag-over {
    border-color: #007bff;
}

input[type="file"] {
    display: none;
}

.pages-container {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 1em;
    margin-top: 1.5em;
    min-height: 100px;
    border: 1px solid #eee;
    padding: 1em;
    border-radius: 8px;
    background-color: #f9f9f9;
}

.page-thumbnail {
    border: 2px solid transparent; /* Changed for selection styling */
    border-radius: 4px;
    overflow: hidden;
    cursor: pointer;
    width: 150px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
    background-color: #fff;
    transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.page-thumbnail.selected {
    border-color: #007bff;
    box-shadow: 0 0 10px rgba(0, 123, 255, 0.5);
    transform: scale(1.05);
}

.page-thumbnail canvas {
    display: block;
    width: 100%;
    height: auto;
}

.page-thumbnail p {
    text-align: center;
    font-size: 0.8em;
    margin: 0.5em 0;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    padding: 0 5px;
}

.controls {
    display: flex;
    justify-content: center;
    gap: 1em;
    margin-top: 2em;
}

button {
    padding: 0.8em 2em;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 1em;
    transition: background-color 0.3s ease, opacity 0.3s ease;
}

#split-btn {
    background-color: #28a745;
    color: #fff;
}

#split-btn:hover:enabled {
    background-color: #218838;
}

#download-all-btn {
    background-color: #f4a261;
    color: #fff;
}

#download-all-btn:hover:enabled {
    background-color: #e76f51;
}

button:disabled {
    background-color: #ccc;
    cursor: not-allowed;
    opacity: 0.6;
}

.status-message {
    text-align: center;
    margin-top: 1em;
    font-weight: bold;
    color: #dc3545;
}