:root {
    --bg-color: #0d1117;
    --panel-bg: #161b22;
    --border-color: #30363d;
    --text-primary: #c9d1d9;
    --text-secondary: #8b949e;
    --accent-color: #58a6ff;
    --accent-hover: #3182ce;
    --danger-color: #f85149;
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-family: var(--font-family);
    line-height: 1.5;
    min-height: 100vh;
}

.app-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem;
    display: flex;
    flex-direction: column;
    height: 100vh;
}

header {
    text-align: center;
    margin-bottom: 2rem;
}

header h1 {
    font-size: 2.5rem;
    font-weight: 600;
    letter-spacing: -0.5px;
    margin-bottom: 0.5rem;
}

.highlight {
    color: var(--accent-color);
    text-shadow: 0 0 15px rgba(88, 166, 255, 0.4);
}

header p {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

.main-content {
    display: flex;
    gap: 2rem;
    flex: 1;
    min-height: 0;
}

/* Controls Panel */
.controls-panel {
    flex: 0 0 400px;
    background-color: var(--panel-bg);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    overflow-y: auto;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.control-group label {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.text-input-group {
    flex: 1 0 auto;
    min-height: 200px;
    display: flex;
    flex-direction: column;
}

.file-upload-actions {
    margin-top: 10px;
    margin-bottom: 20px;
    display: flex;
    gap: 10px;
}

.secondary-btn {
    background-color: var(--panel-bg);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
}

.secondary-btn:hover {
    background-color: var(--border-color);
    border-color: var(--text-secondary);
}

#processFileBtn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    background-color: var(--border-color);
}

.progress-container {
    width: 100%;
}

.progress-bar-bg {
    width: 100%;
    height: 8px;
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 6px;
}

.progress-bar {
    width: 0%;
    height: 100%;
    background-color: var(--accent-color);
    box-shadow: 0 0 10px rgba(88, 166, 255, 0.5);
    transition: width 0.3s ease;
}

.progress-text {
    font-size: 0.85rem;
    color: var(--text-secondary);
    text-align: center;
    font-weight: 500;
}

textarea {
    width: 100%;
    flex: 1;
    min-height: 150px;
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    color: var(--text-primary);
    font-family: var(--font-family);
    padding: 1rem;
    resize: none;
    outline: none;
    transition: border-color 0.2s, box-shadow 0.2s;
    font-size: 1rem;
}

textarea:focus,
select:focus,
input:focus {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 2px rgba(88, 166, 255, 0.2);
}

select,
input[type="number"] {
    width: 100%;
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.75rem 1rem;
    border-radius: 6px;
    font-family: inherit;
    outline: none;
    transition: all 0.2s;
    font-size: 0.95rem;
}

select:disabled,
input:disabled {
    opacity: 0.5;
    background-color: var(--panel-bg);
    cursor: not-allowed;
    border-color: var(--border-color);
    color: var(--text-secondary);
}

.options-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

/* Toggle Switch */
.checkbox-group {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-top: 0.5rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}

.toggle-switch {
    display: flex;
    align-items: center;
    cursor: pointer;
    user-select: none;
}

.toggle-switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.slider {
    position: relative;
    display: inline-block;
    width: 44px;
    height: 24px;
    background-color: var(--border-color);
    border-radius: 24px;
    transition: 0.3s;
    margin-right: 12px;
}

.slider:before {
    position: absolute;
    content: "";
    height: 18px;
    width: 18px;
    left: 3px;
    bottom: 3px;
    background-color: white;
    border-radius: 50%;
    transition: 0.3s;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

input:checked+.slider {
    background-color: var(--accent-color);
}

input:checked+.slider:before {
    transform: translateX(20px);
}

.label-text {
    font-size: 0.95rem;
    font-weight: 500;
}

.header-text-group {
    margin-left: 56px;
}

.header-text-group input[type="text"] {
    width: 100%;
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.5rem 0.75rem;
    border-radius: 6px;
    font-family: inherit;
    font-size: 0.9rem;
    outline: none;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.header-text-group input[type="text"]:focus {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 2px rgba(88, 166, 255, 0.2);
}

/* Preview Panel */
.preview-panel {
    flex: 1;
    background-color: var(--panel-bg);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
}

.preview-header {
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: rgba(22, 27, 34, 0.8);
    backdrop-filter: blur(10px);
}

.preview-header h2 {
    font-size: 1.1rem;
    font-weight: 600;
}

#previewHeaderStatus {
    flex: 1;
    display: flex;
    align-items: center;
}

.primary-btn {
    background-color: var(--accent-color);
    color: white;
    border: none;
    padding: 0.6rem 1.2rem;
    border-radius: 6px;
    font-weight: 600;
    font-size: 0.9rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: all 0.2s;
    font-family: inherit;
}

.primary-btn:hover {
    background-color: var(--accent-hover);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(88, 166, 255, 0.3);
}

.primary-btn:active {
    transform: translateY(0);
}

.canvas-container {
    flex: 1;
    overflow: auto;
    padding: 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2rem;
    background-color: var(--bg-color);
    position: relative;
    /* Checkerboard pattern for transparent canvas background */
    background-image:
        linear-gradient(45deg, #1c2128 25%, transparent 25%),
        linear-gradient(-45deg, #1c2128 25%, transparent 25%),
        linear-gradient(45deg, transparent 75%, #1c2128 75%),
        linear-gradient(-45deg, transparent 75%, #1c2128 75%);
    background-size: 20px 20px;
    background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
}

canvas {
    background-color: white;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
    max-width: 100%;
    height: auto;
    object-fit: contain;
    image-rendering: pixelated;
    /* Ensures sharp pixels when scaled down by CSS */
}

.pages-indicator {
    padding: 0.75rem;
    text-align: center;
    background-color: rgba(22, 27, 34, 0.9);
    border-top: 1px solid var(--border-color);
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.loading-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(13, 17, 23, 0.7);
    backdrop-filter: blur(4px);
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: 1rem;
    z-index: 10;
}

.loading-overlay.active {
    display: flex;
}

.spinner {
    width: 40px;
    height: 40px;
    border: 4px solid var(--border-color);
    border-top-color: var(--accent-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

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

@media (max-width: 900px) {
    .main-content {
        flex-direction: column;
    }

    .controls-panel {
        flex: none;
    }

    .text-input-group {
        min-height: 150px;
    }
}