style.css

/* ==========================================================================
   Design System & Variables
   ========================================================================== */
:root {
    /* Color Palette - Premium Dark Glassmorphism */
    --primary-hue: 220;
    --primary-sat: 90%;
    --primary-light: 60%;

    --color-bg-base: #0f172a;
    --color-bg-sidebar: #0b1120;
    --color-bg-main: #0f172a;

    --color-primary: hsl(var(--primary-hue), var(--primary-sat), var(--primary-light));
    --color-primary-hover: hsl(var(--primary-hue), var(--primary-sat), 70%);
    --color-secondary: #ec4899;
    --color-accent: #8b5cf6;

    --color-text-main: #f8fafc;
    --color-text-muted: #94a3b8;
    --color-text-inverse: #0f172a;

    --color-success: #10b981;
    --color-warning: #f59e0b;
    --color-error: #ef4444;

    /* Glassmorphism */
    --glass-bg: rgba(30, 41, 59, 0.7);
    --glass-border: rgba(255, 255, 255, 0.08);
    --glass-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
    --glass-blur: 12px;

    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;

    /* Typography */
    --font-main: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    --font-serif: 'Noto Serif SC', 'Songti SC', serif;

    /* Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-full: 9999px;

    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.3s ease;

    /* Layout */
    --header-height: 64px;
    --sidebar-width: 300px;
    --toolbar-height: 60px;
}

/* ==========================================================================
   Reset & Base Styles
   ========================================================================== */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: var(--font-main);
    background-color: var(--color-bg-base);
    background-image:
        radial-gradient(circle at 15% 50%, rgba(76, 29, 149, 0.15) 0%, transparent 50%),
        radial-gradient(circle at 85% 30%, rgba(14, 165, 233, 0.15) 0%, transparent 50%);
    background-attachment: fixed;
    color: var(--color-text-main);
    line-height: 1.6;
    height: 100vh;
    overflow: hidden;
    /* Prevent body scroll, use inner scrolling */
}

/* Custom Scrollbar */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.1);
    border-radius: var(--radius-full);
}

::-webkit-scrollbar-thumb:hover {
    background: rgba(255, 255, 255, 0.2);
}

/* ==========================================================================
   App Layout
   ========================================================================== */
.app-container {
    display: flex;
    flex-direction: column;
    height: 100vh;
}

/* Header */
.app-header {
    height: var(--header-height);
    background: rgba(15, 23, 42, 0.8);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--glass-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 var(--spacing-lg);
    z-index: 100;
}

.logo h1 {
    font-size: clamp(0.65rem, 2.5vw, 1.2rem);
    font-weight: 800;
    background: linear-gradient(135deg, var(--color-text-main) 0%, var(--color-primary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: -0.02em;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    max-width: 100%;
}

.header-actions .icon-link {
    color: var(--color-text-muted);
    transition: color var(--transition-fast);
    display: flex;
    align-items: center;
}

.header-actions .icon-link:hover {
    color: var(--color-text-main);
}

/* Main Layout */
.main-layout {
    display: flex;
    flex: 1;
    overflow: hidden;
}

/* Sidebar */
.sidebar {
    width: var(--sidebar-width);
    background: rgba(11, 17, 32, 0.6);
    border-right: 1px solid var(--glass-border);
    display: flex;
    flex-direction: column;
    transition: transform var(--transition-normal);
}

.sidebar-header {
    padding: var(--spacing-md);
    border-bottom: 1px solid var(--glass-border);
}

.sidebar-header h3 {
    font-size: 0.9rem;
    text-transform: uppercase;
    color: var(--color-text-muted);
    letter-spacing: 0.05em;
}

.sidebar-content {
    flex: 1;
    overflow-y: auto;
    padding: var(--spacing-md);
}

/* Content Area */
.content-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    background: rgba(15, 23, 42, 0.3);
    position: relative;
    overflow: hidden;
}

.mode-content {
    display: none;
    flex: 1;
    flex-direction: column;
    height: 100%;
}

.mode-content.active {
    display: flex;
}

/* ==========================================================================
   Toolbar
   ========================================================================== */
.toolbar {
    height: auto;
    min-height: var(--toolbar-height);
    background: rgba(30, 41, 59, 0.4);
    border-bottom: 1px solid var(--glass-border);
    display: flex;
    align-items: center;
    padding: 8px var(--spacing-lg);
    gap: 16px;
    flex-wrap: wrap;
}

.toolbar-group {
    display: flex;
    align-items: center;
    gap: 12px;
    background: rgba(0, 0, 0, 0.2);
    padding: 8px 12px;
    border-radius: var(--radius-md);
    border: 1px solid var(--glass-border);
    box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.3);
}

.toolbar-divider {
    width: 1px;
    height: 32px;
    background: var(--glass-border);
    margin: 0 4px;
}

.toolbar-spacer {
    flex: 1;
}

.tool-item {
    display: flex;
    align-items: center;
    gap: 6px;
    position: relative;
}

.tool-item:not(.inputs) {
    padding: 4px 8px;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.tool-item:not(.inputs):hover {
    background: rgba(255, 255, 255, 0.05);
}

.tool-item label {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    cursor: pointer;
    user-select: none;
}

.tool-item.inputs label {
    margin-right: 0;
}

/* Inputs in Toolbar */
input[type="checkbox"] {
    accent-color: var(--color-primary);
    width: 1rem;
    height: 1rem;
    cursor: pointer;
}

input[type="number"] {
    background: rgba(0, 0, 0, 0.2);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-sm);
    color: var(--color-text-main);
    padding: 2px 6px;
    width: 50px;
    text-align: center;
    font-size: 0.85rem;
    transition: border-color var(--transition-fast);
}

input[type="number"]:focus {
    outline: none;
    border-color: var(--color-primary);
}

input[type="number"]:disabled,
.tool-item.disabled {
    opacity: 0.5;
    pointer-events: none;
}

/* Slider Group Layout */
.slider-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
    align-items: center;
    position: relative;
    padding: 4px 0 8px;
}

.slider-group label {
    margin-right: 0;
    margin-bottom: 2px;
    font-size: 0.85rem;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    font-weight: 500;
}

.slider-group input[type="number"] {
    align-self: center;
    margin-bottom: 6px;
    background: rgba(0, 0, 0, 0.3);
    border: 1px solid var(--glass-border);
    box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.4);
}

/* Slider Container for Scales */
.slider-container {
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100%;
}

/* Slider Scale Lines */
.slider-container::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 140px;
    height: 8px;
    background: linear-gradient(90deg,
            transparent 0%,
            rgba(255, 255, 255, 0.1) 20%,
            rgba(255, 255, 255, 0.1) 40%,
            rgba(255, 255, 255, 0.1) 60%,
            rgba(255, 255, 255, 0.1) 80%,
            transparent 100%);
    background-size: 20% 100%;
    background-repeat: repeat-x;
    pointer-events: none;
    z-index: 1;
}

/* Slider Range Labels */
.slider-range-labels {
    display: flex;
    justify-content: space-between;
    width: 140px;
    margin-top: 4px;
    font-size: 0.7rem;
    color: var(--color-text-muted);
    pointer-events: none;
}

.slider-range-labels .min-label,
.slider-range-labels .max-label {
    opacity: 0.7;
    transition: opacity var(--transition-fast);
}

.slider-group:hover .slider-range-labels .min-label,
.slider-group:hover .slider-range-labels .max-label {
    opacity: 1;
}

/* Slider Styles */
input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    width: 140px;
    height: 8px;
    background: linear-gradient(90deg, rgba(30, 41, 59, 0.6) 0%, rgba(47, 64, 88, 0.4) 100%);
    border-radius: var(--radius-full);
    outline: none;
    transition: all var(--transition-normal);
    box-shadow:
        inset 0 1px 3px rgba(0, 0, 0, 0.4),
        0 1px 2px rgba(255, 255, 255, 0.1);
    cursor: pointer;
}

/* Slider Hover State */
input[type="range"]:hover {
    background: linear-gradient(90deg, rgba(30, 41, 59, 0.8) 0%, rgba(47, 64, 88, 0.6) 100%);
    box-shadow:
        inset 0 1px 3px rgba(0, 0, 0, 0.5),
        0 1px 3px rgba(255, 255, 255, 0.15);
}

/* Slider Focus State */
input[type="range"]:focus {
    background: linear-gradient(90deg, rgba(30, 41, 59, 0.8) 0%, rgba(47, 64, 88, 0.6) 100%);
    box-shadow:
        inset 0 1px 3px rgba(0, 0, 0, 0.5),
        0 0 0 3px rgba(var(--primary-hue), var(--primary-sat), var(--primary-light), 0.2),
        0 1px 3px rgba(255, 255, 255, 0.15);
}

/* Slider Active State (being dragged) */
input[type="range"]:active {
    background: linear-gradient(90deg, rgba(30, 41, 59, 0.9) 0%, rgba(47, 64, 88, 0.7) 100%);
    box-shadow:
        inset 0 1px 4px rgba(0, 0, 0, 0.6),
        0 0 0 3px rgba(var(--primary-hue), var(--primary-sat), var(--primary-light), 0.25),
        0 1px 4px rgba(255, 255, 255, 0.2);
}

/* WebKit Slider Thumb */
input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-hover) 100%);
    border-radius: 6px;
    cursor: pointer;
    box-shadow:
        0 2px 8px rgba(0, 0, 0, 0.3),
        inset 0 1px 2px rgba(255, 255, 255, 0.3),
        inset 0 -1px 2px rgba(0, 0, 0, 0.2);
    transition: all var(--transition-normal);
    position: relative;
}

input[type="range"]::-webkit-slider-thumb::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 6px;
    height: 6px;
    background: rgba(255, 255, 255, 0.6);
    border-radius: 50%;
    box-shadow: 0 0 2px rgba(255, 255, 255, 0.8);
}

input[type="range"]::-webkit-slider-thumb:hover {
    background: linear-gradient(135deg, var(--color-primary-hover) 0%, hsl(var(--primary-hue), var(--primary-sat), 75%) 100%);
    transform: scale(1.25);
    box-shadow:
        0 4px 12px rgba(0, 0, 0, 0.4),
        inset 0 1px 2px rgba(255, 255, 255, 0.3),
        inset 0 -1px 2px rgba(0, 0, 0, 0.2);
}

input[type="range"]::-webkit-slider-thumb:active {
    background: linear-gradient(135deg, hsl(var(--primary-hue), var(--primary-sat), 50%) 0%, hsl(var(--primary-hue), var(--primary-sat), 60%) 100%);
    transform: scale(1.15);
    box-shadow:
        0 2px 6px rgba(0, 0, 0, 0.3),
        inset 0 1px 2px rgba(255, 255, 255, 0.2),
        inset 0 -1px 2px rgba(0, 0, 0, 0.3);
}

/* Firefox Slider Thumb */
input[type="range"]::-moz-range-thumb {
    width: 20px;
    height: 20px;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-hover) 100%);
    border: none;
    border-radius: 6px;
    cursor: pointer;
    box-shadow:
        0 2px 8px rgba(0, 0, 0, 0.3),
        inset 0 1px 2px rgba(255, 255, 255, 0.3),
        inset 0 -1px 2px rgba(0, 0, 0, 0.2);
    transition: all var(--transition-normal);
    position: relative;
}

input[type="range"]::-moz-range-thumb::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 6px;
    height: 6px;
    background: rgba(255, 255, 255, 0.6);
    border-radius: 50%;
    box-shadow: 0 0 2px rgba(255, 255, 255, 0.8);
}

input[type="range"]::-moz-range-thumb:hover {
    background: linear-gradient(135deg, var(--color-primary-hover) 0%, hsl(var(--primary-hue), var(--primary-sat), 75%) 100%);
    transform: scale(1.25);
    box-shadow:
        0 4px 12px rgba(0, 0, 0, 0.4),
        inset 0 1px 2px rgba(255, 255, 255, 0.3),
        inset 0 -1px 2px rgba(0, 0, 0, 0.2);
}

input[type="range"]::-moz-range-thumb:active {
    background: linear-gradient(135deg, hsl(var(--primary-hue), var(--primary-sat), 50%) 0%, hsl(var(--primary-hue), var(--primary-sat), 60%) 100%);
    transform: scale(1.15);
    box-shadow:
        0 2px 6px rgba(0, 0, 0, 0.3),
        inset 0 1px 2px rgba(255, 255, 255, 0.2),
        inset 0 -1px 2px rgba(0, 0, 0, 0.3);
}

/* Slider Track Styles */
input[type="range"]::-moz-range-track {
    background: linear-gradient(90deg, rgba(30, 41, 59, 0.6) 0%, rgba(47, 64, 88, 0.4) 100%);
    height: 8px;
    border-radius: var(--radius-full);
    box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.4), 0 1px 2px rgba(255, 255, 255, 0.1);
}

/* WebKit Slider Track Fill (for browsers that support it) */
input[type="range"]::-webkit-slider-runnable-track {
    -webkit-appearance: none;
    height: 8px;
    background: linear-gradient(90deg, rgba(30, 41, 59, 0.6) 0%, rgba(47, 64, 88, 0.4) 100%);
    border-radius: var(--radius-full);
    box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.4), 0 1px 2px rgba(255, 255, 255, 0.1);
}

/* Disabled Slider Styles */
.tool-item.disabled input[type="range"] {
    opacity: 0.5;
    pointer-events: none;
}

/* Responsive Adjustments */
@media (max-width: 768px) {
    .slider-group {
        width: 100%;
        align-items: center;
    }

    input[type="range"] {
        width: 100%;
        max-width: 200px;
    }
}

/* View Toggle (Edit/Recite) */
.view-toggle {
    display: flex;
    background: rgba(0, 0, 0, 0.2);
    border-radius: var(--radius-md);
    padding: 2px;
    border: 1px solid var(--glass-border);
}

.toggle-btn {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 6px 12px;
    border: none;
    background: transparent;
    color: var(--color-text-muted);
    font-size: 0.85rem;
    font-weight: 500;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.toggle-btn.active {
    background: var(--color-primary);
    color: white;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.toggle-btn:hover:not(.active) {
    color: var(--color-text-main);
    background: rgba(255, 255, 255, 0.05);
}

/* ==========================================================================
   Editor Container (Single Box)
   ========================================================================== */
.editor-container {
    flex: 1;
    position: relative;
    margin: var(--spacing-lg);
    background: rgba(0, 0, 0, 0.2);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: inset 0 2px 10px rgba(0, 0, 0, 0.2);
}

.layer {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease;
    display: flex;
    flex-direction: column;
}

.layer.active {
    opacity: 1;
    visibility: visible;
    z-index: 10;
}

.layer textarea {
    flex: 1;
    width: 100%;
    height: 100%;
    background: transparent;
    border: none;
    padding: var(--spacing-xl);
    color: var(--color-text-main);
    font-family: var(--font-serif);
    font-size: 1.25rem;
    line-height: 2;
    resize: none;
    outline: none;
}

.layer-hint {
    position: absolute;
    bottom: var(--spacing-md);
    right: var(--spacing-md);
    font-size: 0.8rem;
    color: rgba(255, 255, 255, 0.2);
    pointer-events: none;
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

#recite-layer textarea {
    cursor: default;
}

/* ==========================================================================
   Sidebar Lists
   ========================================================================== */
#texts-list-ul {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

#texts-list-ul li {
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    border: 1px solid transparent;
}

#texts-list-ul li:hover {
    background: rgba(255, 255, 255, 0.05);
}

#texts-list-ul li.selected {
    background: rgba(var(--primary-hue), 90%, 60%, 0.15);
    border-color: rgba(var(--primary-hue), 90%, 60%, 0.3);
}

.text-title {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--color-text-main);
}

.text-author {
    font-size: 0.8rem;
    color: var(--color-text-muted);
}

.text-category {
    display: none;
    /* Hide category in sidebar list to save space */
}

/* Semester Selector in Sidebar */
#semester-selector {
    width: 100%;
    background: rgba(0, 0, 0, 0.3);
    border: 1px solid var(--glass-border);
    color: var(--color-text-main);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    margin-bottom: var(--spacing-md);
    font-size: 0.9rem;
    font-weight: 500;
    transition: all var(--transition-fast);
    cursor: pointer;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%2394a3b8' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right var(--spacing-md) center;
    background-size: 16px;
}

#semester-selector:hover {
    background-color: rgba(0, 0, 0, 0.4);
    border-color: rgba(255, 255, 255, 0.15);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
}

#semester-selector:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(var(--primary-hue), var(--primary-sat), var(--primary-light), 0.15);
}

#semester-selector option {
    background: var(--color-bg-sidebar);
    color: var(--color-text-main);
    padding: var(--spacing-sm);
    font-size: 0.9rem;
}

#semester-selector option:hover {
    background: var(--color-primary);
    color: white;
}

/* Paragraphs View in Sidebar */
.content-view {
    display: none;
}

.content-view.active {
    display: block;
    animation: fadeIn var(--transition-fast);
}

.paragraphs-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
    padding-bottom: var(--spacing-sm);
    border-bottom: 1px solid var(--glass-border);
}

.icon-btn {
    background: transparent;
    border: none;
    color: var(--color-text-muted);
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 4px;
    padding: 4px 8px;
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
}

.icon-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    color: var(--color-text-main);
}

.paragraph-card {
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-md);
    padding: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
}

.paragraph-card h5 {
    font-size: 0.8rem;
    color: var(--color-text-muted);
    margin-bottom: 4px;
}

.paragraph-preview {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
    margin-bottom: 8px;
}

.select-paragraph-btn,
.select-all-btn {
    width: 100%;
    padding: 6px;
    font-size: 0.8rem;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--glass-border);
    color: var(--color-text-main);
    border-radius: var(--radius-sm);
    cursor: pointer;
}

.select-paragraph-btn:hover,
.select-all-btn:hover {
    background: rgba(255, 255, 255, 0.1);
}

/* ==========================================================================
   Review Mode Styles
   ========================================================================== */
.review-container {
    max-width: 800px;
    margin: 0 auto;
    padding: var(--spacing-xl);
    width: 100%;
    overflow-y: auto;
}

.review-header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.review-controls {
    display: flex;
    justify-content: center;
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.btn-primary {
    background: var(--color-primary);
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: var(--radius-md);
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: background var(--transition-fast);
}

.btn-primary:hover {
    background: var(--color-primary-hover);
}

.checkbox-btn {
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    user-select: none;
}

.review-sentence {
    background: rgba(0, 0, 0, 0.2);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
    border-left: 4px solid var(--color-primary);
    position: relative;
}

.sentence-number {
    position: absolute;
    top: -10px;
    left: -10px;
    width: 28px;
    height: 28px;
    background: var(--color-primary);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 0.85rem;
}

.sentence-content {
    font-family: var(--font-serif);
    font-size: 1.2rem;
    line-height: 1.8;
    display: block;
    margin-bottom: var(--spacing-sm);
}

.blank {
    border-bottom: 2px solid var(--color-primary);
    color: transparent;
    cursor: pointer;
    padding: 0 4px;
    transition: all 0.2s;
}

.blank:hover {
    background: rgba(var(--primary-hue), 90%, 60%, 0.1);
}

.blank.revealed {
    color: var(--color-success);
    border-bottom-color: var(--color-success);
}

/* ==========================================================================
   Mode Switch (Top Right)
   ========================================================================== */
.mode-switch {
    display: flex;
    align-items: center;
    background: rgba(0, 0, 0, 0.2);
    padding: 4px 12px;
    border-radius: var(--radius-full);
    border: 1px solid var(--glass-border);
}

.mode-label {
    font-size: 0.8rem;
    color: var(--color-text-muted);
    transition: color 0.3s;
}

.switch {
    position: relative;
    display: inline-block;
    width: 40px;
    height: 20px;
    margin: 0 10px;
}

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

.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(255, 255, 255, 0.1);
    transition: .4s;
    border-radius: 34px;
}

.slider:before {
    position: absolute;
    content: "";
    height: 14px;
    width: 14px;
    left: 3px;
    bottom: 3px;
    background-color: white;
    transition: .4s;
    border-radius: 50%;
}

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

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

/* Active label highlighting */
body.review-mode-active .mode-switch .mode-label:first-child,
body:not(.review-mode-active) .mode-switch .mode-label:last-child {
    color: var(--color-text-main);
    font-weight: 700;
}

/* ==========================================================================
   Mobile Responsive
   ========================================================================== */
.mobile-fab {
    display: none;
}

@media (max-width: 768px) {
    .app-container {
        height: auto;
        min-height: 100vh;
    }

    .main-layout {
        flex-direction: column;
        overflow: visible;
    }

    .sidebar {
        width: 100%;
        height: 300px;
        /* Fixed height for sidebar on mobile */
        border-right: none;
        border-bottom: 1px solid var(--glass-border);
    }

    .content-area {
        height: auto;
        min-height: 500px;
    }

    .toolbar {
        height: auto;
        flex-wrap: wrap;
        padding: var(--spacing-md);
        gap: var(--spacing-sm);
    }

    .toolbar-divider {
        display: none;
    }

    .toolbar-spacer {
        display: none;
    }

    .view-toggle {
        width: 100%;
        margin-top: var(--spacing-sm);
    }

    .toggle-btn {
        flex: 1;
        justify-content: center;
    }

    .editor-container {
        margin: var(--spacing-md);
        min-height: 400px;
    }

    /* Slider Responsive Adjustments */
    .toolbar-group {
        width: 100%;
        justify-content: space-around;
        gap: 8px;
    }

    .slider-group {
        flex: 1;
        min-width: 120px;
    }

    .slider-container {
        width: 100%;
    }

    input[type="range"] {
        width: 100%;
        max-width: 180px;
    }

    .slider-container::before {
        width: 100%;
        max-width: 180px;
    }

    .slider-range-labels {
        width: 100%;
        max-width: 180px;
        font-size: 0.65rem;
    }

    .slider-group label {
        font-size: 0.8rem;
    }

    .slider-group input[type="number"] {
        width: 45px;
        font-size: 0.8rem;
        padding: 2px 4px;
    }
}

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

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ==========================================================================
   Combo Control (Button + Dropdown)
   ========================================================================== */
.combo-control {
    display: flex;
    align-items: center;
    background: rgba(0, 0, 0, 0.4);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-md);
    position: relative;
    transition: all var(--transition-normal);
    color: var(--color-text-muted);
}

.combo-control.active {
    background: var(--color-primary);
    color: white;
    /* Force white for better contrast on primary */
    border-color: transparent;
    box-shadow: 0 4px 12px rgba(var(--primary-hue), var(--primary-sat), 50%, 0.3);
}

.combo-main {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 12px;
    cursor: pointer;
    border-top-left-radius: var(--radius-md);
    border-bottom-left-radius: var(--radius-md);
    user-select: none;
    transition: background var(--transition-fast);
}

.combo-main:hover {
    background: rgba(255, 255, 255, 0.05);
}

.combo-control.active .combo-main:hover {
    background: rgba(0, 0, 0, 0.1);
}

/* Custom Checkbox in Combo */
.custom-checkbox {
    width: 18px;
    height: 18px;
    border: 2px solid currentColor;
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
    opacity: 0.7;
}

.custom-checkbox svg {
    opacity: 0;
    transform: scale(0.5);
    transition: all 0.2s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.combo-control.active .custom-checkbox {
    background: white;
    border-color: white;
    color: var(--color-primary);
    opacity: 1;
}

.combo-control.active .custom-checkbox svg {
    opacity: 1;
    transform: scale(1);
}

.combo-label {
    font-size: 0.9rem;
    font-weight: 500;
}

/* Vertical Separator */
.combo-separator {
    width: 1px;
    height: 20px;
    background: currentColor;
    opacity: 0.2;
}

.combo-control.active .combo-separator {
    opacity: 0.3;
}

/* Dropdown Trigger Arrow */
.combo-trigger {
    padding: 8px 10px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    border-top-right-radius: var(--radius-md);
    border-bottom-right-radius: var(--radius-md);
    transition: background var(--transition-fast);
}

.combo-trigger:hover {
    background: rgba(255, 255, 255, 0.05);
}

.combo-control.active .combo-trigger:hover {
    background: rgba(0, 0, 0, 0.1);
}

/* Dropdown Menu */
.combo-dropdown {
    position: absolute;
    top: calc(100% + 8px);
    right: 0;
    width: 180px;
    background: rgba(15, 23, 42, 0.95);
    backdrop-filter: blur(16px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-md);
    padding: var(--spacing-sm);
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.5), 0 8px 10px -6px rgba(0, 0, 0, 0.5);
    /* Stronger shadow for popover */
    z-index: 1000;

    /* Animation state: hidden */
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Show Dropdown */
.combo-dropdown.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.dropdown-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 12px;
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: background var(--transition-fast);
    color: var(--color-text-main);
}

.dropdown-item:hover {
    background: rgba(255, 255, 255, 0.1);
}

.dropdown-item input[type="checkbox"] {
    accent-color: var(--color-primary);
    width: 16px;
    height: 16px;
    cursor: pointer;
}

.dropdown-item span {
    font-size: 0.9rem;
}

/* =========================================================================
   生疏本功能样式
   ========================================================================= */

/* 查看生疏本按钮 */
.btn-secondary {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 20px;
    background: rgba(30, 41, 59, 0.6);
    color: var(--color-text-muted);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-secondary:hover {
    background: rgba(30, 41, 59, 0.8);
    border-color: var(--color-primary);
    color: var(--color-text-main);
}

/* 句子卡片上的标记/收藏按钮 */
.sentence-actions {
    position: absolute;
    right: 15px;
    top: 50%;
    transform: translateY(-50%);
    display: flex;
    align-items: center;
}

.mark-btn {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--color-text-muted);
    padding: 8px;
    border-radius: 50%;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0.6;
}

.mark-btn:hover {
    background-color: rgba(255, 255, 255, 0.1);
    color: var(--color-text-main);
    opacity: 1;
}

/* 选中状态 */
.mark-btn.active {
    color: #ef4444;
    opacity: 1;
}

.mark-btn.active svg {
    fill: #ef4444;
}

.review-sentence {
    position: relative;
    padding-right: 50px;
}

/* =========================================================================
   模态窗口 (Modal) 样式
   ========================================================================= */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(4px);
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
}

.modal-overlay:not(.hidden) {
    opacity: 1;
    visibility: visible;
}

.modal-container {
    background-color: var(--color-bg-base);
    border: 1px solid var(--glass-border);
    width: 90%;
    max-width: 900px;
    height: 80vh;
    border-radius: var(--radius-lg);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    transform: scale(0.95);
    transition: transform 0.3s ease;
}

.modal-overlay:not(.hidden) .modal-container {
    transform: scale(1);
}

.modal-header {
    padding: 20px 24px;
    border-bottom: 1px solid var(--glass-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: rgba(15, 23, 42, 0.6);
}

.modal-header h3 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--color-text-main);
    margin: 0;
}

.modal-header-actions {
    display: flex;
    align-items: center;
    gap: 12px;
}

/* 清空存储按钮 */
.btn-clear-storage {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 8px 14px;
    background: rgba(239, 68, 68, 0.15);
    color: var(--color-error);
    border: 1px solid rgba(239, 68, 68, 0.3);
    border-radius: var(--radius-md);
    font-size: 0.85rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-clear-storage:hover {
    background: rgba(239, 68, 68, 0.25);
    border-color: rgba(239, 68, 68, 0.5);
}

.btn-clear-storage svg {
    flex-shrink: 0;
}

.close-btn {
    padding: 4px;
    border-radius: var(--radius-sm);
    transition: background 0.2s;
}

.close-btn:hover {
    background: rgba(255, 255, 255, 0.1);
}

.modal-body {
    flex: 1;
    display: flex;
    overflow: hidden;
}

/* 侧边栏：篇目导航 */
.unknown-cards-sidebar {
    width: 260px;
    border-right: 1px solid var(--glass-border);
    overflow-y: auto;
    background: rgba(11, 17, 32, 0.4);
}

.unknown-cards-sidebar ul {
    list-style: none;
    padding: 12px;
    margin: 0;
}

.unknown-cards-sidebar li {
    padding: 12px 14px;
    margin-bottom: 6px;
    border-radius: var(--radius-md);
    cursor: pointer;
    font-size: 0.95rem;
    color: var(--color-text-muted);
    transition: all 0.2s;
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.unknown-cards-sidebar li:hover {
    background-color: rgba(255, 255, 255, 0.05);
    color: var(--color-text-main);
}

.unknown-cards-sidebar li.active {
    background-color: rgba(var(--primary-hue), 90%, 60%, 0.15);
    color: var(--color-primary);
    font-weight: 500;
}

.source-title-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.source-title-row .count {
    background-color: rgba(0, 0, 0, 0.3);
    padding: 2px 8px;
    border-radius: 10px;
    font-size: 0.75rem;
    min-width: 20px;
    text-align: center;
}

.unknown-cards-sidebar li.active .count {
    background-color: var(--color-primary);
    color: white;
}

/* 熟悉度条 */
.familiarity-bar {
    height: 6px;
    border-radius: 3px;
    background: rgba(0, 0, 0, 0.3);
    overflow: hidden;
    display: flex;
}

.familiarity-bar .familiar-segment {
    background: var(--color-success);
    height: 100%;
}

.familiarity-bar .unknown-segment {
    background: var(--color-error);
    height: 100%;
}

/* 内容区域 */
.unknown-cards-content {
    flex: 1;
    padding: 24px;
    overflow-y: auto;
    background: transparent;
}

.unknown-card-item {
    background: rgba(30, 41, 59, 0.3);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-md);
    padding: 20px;
    margin-bottom: 16px;
    position: relative;
    transition: transform 0.2s, box-shadow 0.2s;
}

.unknown-card-item:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
    border-color: rgba(255, 255, 255, 0.1);
}

.unknown-card-item .item-content {
    font-size: 1.1rem;
    margin-bottom: 8px;
    line-height: 1.8;
    font-family: var(--font-serif);
    padding-right: 40px;
}

.unknown-card-item .item-source {
    font-size: 0.85rem;
    color: var(--color-text-muted);
}

.unknown-card-item .remove-btn {
    position: absolute;
    top: 10px;
    right: 10px;
    border: none;
    background: transparent;
    color: rgba(255, 255, 255, 0.3);
    cursor: pointer;
    padding: 4px;
    border-radius: var(--radius-sm);
    transition: all 0.2s;
    line-height: 0;
}

.unknown-card-item .remove-btn svg {
    width: 14px;
    height: 14px;
}

.unknown-card-item .remove-btn:hover {
    color: rgba(255, 255, 255, 0.8);
    background: rgba(255, 255, 255, 0.1);
}

.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100%;
    color: var(--color-text-muted);
    text-align: center;
    padding: 40px;
}

.empty-state svg {
    margin-bottom: 16px;
    color: rgba(255, 255, 255, 0.1);
}

.empty-state p {
    font-size: 1.1rem;
    margin: 0 0 8px 0;
}

.empty-state p.sub-text {
    font-size: 0.9rem;
    opacity: 0.6;
}

/* 响应式适配 */
@media (max-width: 768px) {
    .modal-container {
        width: 100%;
        height: 100%;
        border-radius: 0;
        max-width: none;
    }

    .modal-body {
        flex-direction: column;
    }

    .unknown-cards-sidebar {
        width: 100%;
        height: auto;
        min-height: 60px;
        max-height: 180px;
        border-right: none;
        border-bottom: 1px solid var(--glass-border);
    }

    .unknown-cards-sidebar ul {
        display: flex;
        overflow-x: auto;
        padding: 8px;
        gap: 8px;
    }

    .unknown-cards-sidebar li {
        white-space: nowrap;
        margin-bottom: 0;
        flex-shrink: 0;
    }

    .modal-header h3 {
        font-size: 1.1rem;
    }
}

/* ==========================================================================
   Mobile Device Styles (based on User Agent detection)
   Uses .is-mobile class instead of media queries
   ========================================================================== */

/* Hamburger Menu Button - Hidden on Desktop */
.sidebar-toggle-btn {
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: 5px;
    width: 40px;
    height: 40px;
    background: transparent;
    border: none;
    cursor: pointer;
    padding: 8px;
    border-radius: var(--radius-md);
    transition: background var(--transition-fast);
}

.sidebar-toggle-btn span {
    display: block;
    width: 22px;
    height: 2px;
    background: var(--color-text-main);
    border-radius: 2px;
    transition: all var(--transition-normal);
}

.sidebar-toggle-btn:hover {
    background: rgba(255, 255, 255, 0.1);
}

/* Hamburger to X animation */
.sidebar-toggle-btn.active span:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
}

.sidebar-toggle-btn.active span:nth-child(2) {
    opacity: 0;
}

.sidebar-toggle-btn.active span:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
}

/* Sidebar Overlay - Hidden by default */
.sidebar-overlay {
    display: none;
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(4px);
    z-index: 90;
    opacity: 0;
    visibility: hidden;
    transition: opacity var(--transition-normal), visibility var(--transition-normal);
}

.sidebar-overlay.active {
    opacity: 1;
    visibility: visible;
}

/* ==========================================================================
   Mobile Device Only Styles
   ========================================================================== */
.is-mobile .sidebar-toggle-btn {
    display: flex;
}

.is-mobile .sidebar-overlay {
    display: block;
}

/* Mobile Sidebar - Drawer Style */
.is-mobile .sidebar {
    position: fixed;
    top: var(--header-height);
    left: 0;
    height: 80vh;
    width: 85%;
    max-width: 320px;
    z-index: 95;
    transform: translateX(-100%);
    transition: transform var(--transition-normal);
    box-shadow: 4px 0 20px rgba(0, 0, 0, 0.3);
    border-bottom-right-radius: var(--radius-lg);
}

.is-mobile .sidebar.open {
    transform: translateX(0);
}

/* Mobile Header Adjustments */
.is-mobile .app-header {
    padding: 0 var(--spacing-sm);
}

.is-mobile .logo h1 {
    font-size: 1.2rem;
}

/* Mobile Mode Switch - Compact */
.is-mobile .mode-switch-container {
    flex: 1;
    display: flex;
    justify-content: center;
}

.is-mobile .mode-switch {
    transform: scale(0.85);
}

.is-mobile .mode-label {
    font-size: 0.75rem;
}

/* Mobile Scroll Support */
.is-mobile body,
body.is-mobile {
    overflow: auto;
    height: auto;
    min-height: 100vh;
}

.is-mobile .app-container {
    height: auto;
    min-height: 100vh;
}

.is-mobile .content-area {
    overflow-y: auto;
    overflow-x: hidden;
    -webkit-overflow-scrolling: touch;
}

.is-mobile .mode-content {
    height: auto;
    min-height: calc(100vh - var(--header-height));
    overflow-y: visible;
}

.is-mobile .mode-content.active {
    display: block;
}

.is-mobile #review-mode {
    padding-bottom: 80px;
}

/* Mobile Main Layout */
.is-mobile .main-layout {
    flex-direction: column;
}

/* Mobile Toolbar - Compact */
.is-mobile .toolbar {
    padding: var(--spacing-sm);
    gap: var(--spacing-sm);
    flex-wrap: wrap;
    justify-content: center;
}

.is-mobile .toolbar-group {
    padding: 6px 10px;
    gap: 8px;
}

.is-mobile .toolbar-divider {
    display: none;
}

.is-mobile .toolbar-spacer {
    display: none;
}

.is-mobile .slider-group {
    display: none;
}

.is-mobile .slider-range-labels {
    display: none;
}

.is-mobile input[type="range"] {
    display: none;
}

.is-mobile .tool-item.inputs input[type="number"] {
    width: 45px;
    padding: 4px;
    font-size: 0.8rem;
}

.is-mobile .tool-item label {
    font-size: 0.8rem;
}

.is-mobile .view-toggle {
    width: 100%;
    justify-content: center;
    margin-top: var(--spacing-sm);
}

/* Mobile Editor Container */
.is-mobile .editor-container {
    margin: var(--spacing-sm);
}

.is-mobile .layer textarea {
    padding: var(--spacing-md);
    font-size: 1.1rem;
    line-height: 1.8;
}

/* Mobile Review Mode */
.is-mobile .review-container {
    padding: var(--spacing-md);
}

.is-mobile .review-header {
    padding: var(--spacing-md);
}

.is-mobile .review-header h2 {
    font-size: 1.3rem;
}

.is-mobile .review-header p {
    font-size: 0.85rem;
}

.is-mobile .review-controls {
    flex-direction: column;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm);
}

.is-mobile .review-controls .btn-primary,
.is-mobile .review-controls .btn-secondary {
    width: 100%;
    justify-content: center;
}

.is-mobile .combo-control {
    width: 100%;
}

.is-mobile .combo-main {
    flex: 1;
}

/* Mobile Review Sentences */
.is-mobile .review-sentence {
    padding: var(--spacing-md);
}

.is-mobile .sentence-content {
    font-size: 1rem;
    line-height: 1.7;
}

.is-mobile .source-info {
    font-size: 0.75rem;
}

.is-mobile .sentence-actions {
    margin-top: var(--spacing-sm);
    flex-wrap: wrap;
    gap: var(--spacing-xs);
}

.is-mobile .sentence-actions button {
    padding: 6px 10px;
    font-size: 0.75rem;
}

/* Mobile Modal */
.is-mobile .modal-container {
    width: 100%;
    height: 100%;
    border-radius: 0;
    max-width: none;
}

.is-mobile .modal-body {
    flex-direction: column;
}

.is-mobile .unknown-cards-sidebar {
    width: 100%;
    height: auto;
    min-height: 60px;
    max-height: 150px;
    border-right: none;
    border-bottom: 1px solid var(--glass-border);
}

.is-mobile .unknown-cards-sidebar ul {
    display: flex;
    overflow-x: auto;
    padding: var(--spacing-sm);
    gap: var(--spacing-sm);
}

.is-mobile .unknown-cards-sidebar li {
    white-space: nowrap;
    margin-bottom: 0;
    flex-shrink: 0;
}

/* 移动端模态窗口头部 */
.is-mobile .modal-header {
    padding: 16px;
}

.is-mobile .modal-header h3 {
    font-size: 1.1rem;
}

.is-mobile .modal-header-actions {
    gap: 8px;
}

.is-mobile .btn-clear-storage {
    padding: 6px 10px;
    font-size: 0.8rem;
}

.is-mobile .btn-clear-storage span {
    display: none;
}

/* 移动端卡片删除按钮优化 */
.is-mobile .unknown-card-item .remove-btn {
    padding: 8px;
}

/* Mobile FAB Button */
.is-mobile .mobile-fab {
    display: flex;
}

/* Mobile Header and Logo Title */
.is-mobile .app-header {
    padding: 0 var(--spacing-sm);
    gap: var(--spacing-xs);
    height: auto;
    min-height: var(--header-height);
    flex-wrap: wrap;
}

.is-mobile .logo {
    flex: 1;
    min-width: 0;
    overflow: visible;
}

.is-mobile .logo h1 {
    font-size: clamp(0.45rem, 3vw, 0.85rem);
    white-space: normal;
    overflow: visible;
    text-overflow: clip;
    line-height: 1.3;
    word-break: break-word;
}

/* ==========================================================================
   Accessibility: Reduced Motion
   ========================================================================== */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* ==========================================================================
   Accessibility: Focus Visible
   ========================================================================== */
:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
    border-radius: var(--radius-sm);
}

button:focus-visible,
.toggle-btn:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
    box-shadow: 0 0 0 4px rgba(76, 110, 245, 0.2);
}

input[type="checkbox"]:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

textarea:focus-visible {
    outline: none;
    box-shadow: inset 0 0 0 2px var(--color-primary);
}

/* ==========================================================================
   Accessibility: Screen Reader Only
   ========================================================================== */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}