:root {
    /* Light Mode (Default) */
    --bg: #f8fafc;
    --card-bg: #ffffff;
    --primary: #0f172a;
    --primary-hover: #334155;
    --accent: #3b82f6;
    --text-main: #0f172a;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --tab-bg: #f1f5f9;
    --drag-active-bg: #eff6ff;
}

[data-theme="dark"] {
    /* Dark Mode */
    --bg: #0f172a;
    --card-bg: #1e293b;
    --primary: #3b82f6;
    --primary-hover: #60a5fa;
    --accent: #60a5fa;
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --border: #334155;
    --tab-bg: #0f172a;
    --drag-active-bg: #1e3a5f;
}

body {
    background-color: var(--bg);
    color: var(--text-main);
    transition: background-color 0.3s ease, color 0.3s ease;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
}

/* Dark Mode Toggle Button Styles */
.theme-toggle {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: var(--tab-bg);
    border: 1px solid var(--border);
    color: var(--text-main);
    padding: 0.5rem;
    border-radius: 50%;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 1.2rem;
}

.container {
    background: var(--card-bg);
    padding: 2.5rem;
    border-radius: 12px;
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.05), 0 8px 10px -6px rgba(0, 0, 0, 0.01);
    width: 100%;
    max-width: 450px;
    border: 1px solid var(--border);
}

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

.app-header .icon {
    width: 48px;
    height: 48px;
    color: var(--accent);
    margin-bottom: 0.5rem;
}

h2 { margin: 0 0 0.5rem 0; font-size: 1.5rem; font-weight: 700; }
p { margin: 0; color: var(--text-muted); font-size: 0.9rem; }

/* Drag and Drop Area */
.file-drop {
    border: 2px dashed var(--border);
    padding: 2rem 1rem;
    border-radius: 8px;
    text-align: center;
    background-color: var(--bg);
    transition: all 0.2s ease;
    margin-bottom: 1.5rem;
}

.file-drop.drag-active {
    border-color: var(--accent);
    background-color: var(--drag-active-bg);
}

.upload-icon {
    width: 32px;
    height: 32px;
    color: var(--text-muted);
    margin-bottom: 0.5rem;
}

.text-sm {
    display: block;
    font-size: 0.8rem;
    color: var(--text-muted);
    margin: 0.5rem 0;
}

/* Lists and Buttons */
.file-list {
    list-style: none;
    padding: 0;
    margin: 0 0 1.5rem 0;
    max-height: 120px;
    overflow-y: auto;
}

.file-list li {
    font-size: 0.85rem;
    padding: 0.5rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 4px;
    margin-bottom: 0.5rem;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

button {
    font-family: inherit;
    font-size: 1rem;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s ease;
    font-weight: 600;
}

.secondary-btn {
    background: transparent;
    color: var(--accent);
    border: 1px solid var(--accent);
    padding: 0.4rem 1rem;
    font-size: 0.85rem;
}

.secondary-btn:hover { background: #eff6ff; }

.primary-btn {
    width: 100%;
    background-color: var(--primary);
    color: white;
    border: none;
    padding: 0.85rem;
}

.primary-btn:hover:not(:disabled) { background-color: var(--primary-hover); }
.primary-btn:disabled { background-color: var(--text-muted); cursor: not-allowed; opacity: 0.7; }

.status-message {
    margin-top: 1.25rem;
    font-size: 0.85rem;
    font-weight: 600;
    text-align: center;
    color: var(--text-muted);
}

.text-green { color: #059669; }
.text-red { color: #dc2626; }

/* Tab Navigation — horizontally scrollable for many tools */
.tabs {
    display: flex;
    gap: 0.35rem;
    margin-bottom: 1.5rem;
    background: #f1f5f9;
    padding: 0.3rem;
    border-radius: 8px;
    overflow-x: auto;
    -ms-overflow-style: none;
    scrollbar-width: none;
}
.tabs::-webkit-scrollbar { display: none; }

[data-theme="dark"] .tabs { background: var(--tab-bg); }

.tab-btn {
    flex-shrink: 0;
    background: transparent;
    color: var(--text-muted);
    border: none;
    padding: 0.45rem 0.7rem;
    font-weight: 600;
    font-size: 0.8rem;
    white-space: nowrap;
    border-radius: 5px;
}

.tab-btn.active {
    background: white;
    color: var(--primary);
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

[data-theme="dark"] .tab-btn.active { background: var(--card-bg); }

.hidden-tool { display: none; }
.active-tool { display: block; animation: fadeIn 0.3s ease; }

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(5px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Input Fields */
.input-group {
    margin-bottom: 1.5rem;
    text-align: left;
}

.input-group label {
    display: block;
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 0.4rem;
}

.text-input {
    width: 90%;
    padding: 0.75rem;
    border: 1px solid var(--border);
    border-radius: 6px;
    font-family: inherit;
    font-size: 0.95rem;
}

.text-input:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

/* Thumbnail Grid Styles */
.thumbnail-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
    gap: 1rem;
    margin-bottom: 1.5rem;
    max-height: 400px;
    overflow-y: auto;
    padding: 0.5rem;
    background: #f8fafc;
    border-radius: 8px;
    border: 1px solid var(--border);
}

.thumbnail-grid:empty {
    display: none;
}

.thumbnail-item {
    position: relative;
    cursor: grab;
    background: white;
    padding: 0.25rem;
    border: 1px solid var(--border);
    border-radius: 4px;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    transition: transform 0.2s, box-shadow 0.2s;
}

.thumbnail-item:active {
    cursor: grabbing;
}

.thumbnail-item:hover {
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    transform: translateY(-2px);
    border-color: var(--accent);
}

.thumbnail-item canvas {
    width: 100%;
    height: auto;
    display: block;
    border: 1px solid #e2e8f0;
}

/* The visual badge showing the original page number */
.page-badge {
    position: absolute;
    top: -8px;
    right: -8px;
    background: var(--primary);
    color: white;
    font-size: 0.75rem;
    font-weight: bold;
    width: 22px;
    height: 22px;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 50%;
    box-shadow: 0 2px 4px rgba(0,0,0,0.2);
}

/* Style for the empty space when dragging an item */
.sortable-ghost {
    opacity: 0.4;
    background-color: #eff6ff;
    border: 2px dashed var(--accent);
}

/* ── Sortable merge file list items ── */
.file-list-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.85rem;
    padding: 0.4rem 0.5rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 4px;
    margin-bottom: 0.4rem;
}

.drag-handle {
    cursor: grab;
    color: var(--text-muted);
    font-size: 1rem;
    user-select: none;
    flex-shrink: 0;
    line-height: 1;
}
.drag-handle:active { cursor: grabbing; }

.file-name {
    flex: 1;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    min-width: 0;
}

.remove-file-btn {
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 1.1rem;
    padding: 0 0.15rem;
    cursor: pointer;
    font-weight: 700;
    flex-shrink: 0;
    line-height: 1;
    transition: color 0.15s ease;
}
.remove-file-btn:hover { color: #dc2626; }

/* ── Password input ── */
.password-input {
    display: block;
    width: calc(100% - 1.5rem);
    padding: 0.5rem 0.75rem;
    margin-bottom: 1rem;
    border: 1px solid var(--border);
    border-radius: 6px;
    background: var(--bg);
    color: var(--text-main);
    font-family: inherit;
    font-size: 0.85rem;
    transition: border-color 0.2s ease;
}
.password-input:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}
.password-input::placeholder { color: var(--text-muted); }

/* ── Range preview (Split tool) ── */
.range-preview {
    display: block;
    font-size: 0.8rem;
    font-weight: 600;
    margin-top: 0.35rem;
    min-height: 1.1em;
}

/* ── Split options (multi-file toggle) ── */
.split-options {
    margin-bottom: 1rem;
}

.toggle-label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    color: var(--text-main);
    user-select: none;
}
.toggle-label input[type="checkbox"] {
    width: 15px;
    height: 15px;
    accent-color: var(--accent);
    cursor: pointer;
    flex-shrink: 0;
}

.split-help {
    display: block;
    font-size: 0.78rem;
    color: var(--text-muted);
    margin-top: 0.3rem;
    padding-left: 1.4rem;
}

/* ── Select / number inputs (new tools) ── */
select.text-input {
    appearance: none;
    -webkit-appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%2364748b' d='M6 8L1 3h10z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 0.75rem center;
    padding-right: 2rem;
    cursor: pointer;
    background-color: var(--bg);
    color: var(--text-main);
}

.num-input {
    width: 6rem;
}

/* ── Footer ── */
.app-footer {
    text-align: center;
    margin-top: 1.5rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border);
    font-size: 0.78rem;
    color: var(--text-muted);
}

.app-footer strong {
    color: var(--text-main);
}

/* ── Inspect tool ── */
.inspect-results {
    margin: 1rem 0;
    border: 1px solid var(--border);
    border-radius: 8px;
    overflow: hidden;
    font-size: 0.83rem;
}

.inspect-results:empty { display: none; }

.inspect-section-title {
    background: var(--bg);
    padding: 0.35rem 0.75rem;
    font-size: 0.72rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    border-bottom: 1px solid var(--border);
}

.inspect-row {
    display: flex;
    padding: 0.4rem 0.75rem;
    border-bottom: 1px solid var(--border);
    gap: 0.5rem;
    align-items: baseline;
}

.inspect-row:last-child { border-bottom: none; }

.inspect-key {
    font-weight: 600;
    color: var(--text-muted);
    min-width: 90px;
    flex-shrink: 0;
    font-size: 0.8rem;
}

.inspect-val {
    color: var(--text-main);
    word-break: break-word;
}

.inspect-val.empty { color: var(--text-muted); font-style: italic; }
.inspect-val.highlight { color: var(--accent); font-weight: 700; }
.inspect-val.warn { color: #d97706; font-weight: 600; }

/* ── Opacity range slider (Watermark tool) ── */
.range-slider {
    display: block;
    width: 100%;
    margin-top: 0.4rem;
    accent-color: var(--accent);
    cursor: pointer;
}