:root {
    --primary: #4a6fa5;
    --secondary: #166088;
    --light: #f8f9fa;
    --dark: #343a40;
    --success: #28a745;
    --danger: #dc3545;
    --warning: #ffc107;

    --cards-highlight-bg: #e9f2ff;
    --cards-highlight-border: #92b5e3;
    --cards-hover-bg: #f0f5ff;
    --success-bg: #d4edda;
    --danger-bg: #f8d7da;
    --warning-bg: #fff3cd;
    --disabled-bg: #ccc;
    --progress-track: #e9ecef;
    --explanation-bg: #e7f3ff;
    --explanation-hover-bg: #d0e9ff;
    --explanation-border: #2196f3;
    --explanation-border-light: #90caf9;
    --explanation-text: #1565c0;
    --explanation-content-text: #0d47a1;
    --tooltip-bg: #1565c0;
    --btn-secondary-bg: #6c757d;
    --btn-secondary-hover: #5a6268;
    --sr-gradient-start: #4a6fa5;
    --sr-gradient-end: #166088;
    --sr-gradient-hover-start: #3d5d8c;
    --sr-gradient-hover-end: #124d6f;
    --sr-info-color: #17a2b8;
    --sr-info-hover: #138496;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--dark);
    background-color: var(--surface-secondary);
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

.container {
    width: 90%;
    max-width: 900px;
    margin: 1rem auto;
    flex: 1;
}

.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
    margin-bottom: 0;
    padding: 0.75rem 1rem;
    background-color: var(--surface-color);
    border-radius: 8px 8px 0 0;
    box-shadow: 0 2px 4px var(--shadow-color);
}

.header-content {
    flex: 2;
    text-align: center;
}

.header h1 {
    color: var(--primary);
    margin: 0.5rem 0 0 0;
    font-size: 1.2rem;
}

.header p {
    margin: 0.25rem 0;
    font-size: 1.05rem;
}

#file-input-container {
    margin-bottom: 1rem;
    text-align: center;
}

#file-input {
    display: none;
}

/* Saved Decks Styles */
#saved-decks {
    margin: 1rem 0;
}

.saved-deck {
    background-color: var(--surface-color);
    padding: 0.5rem;
    margin-bottom: 0.5rem;
    border-radius: 4px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 1px 3px var(--shadow-color);
}

.deck-title {
    font-weight: 500;
    color: var(--primary);
    cursor: pointer;
}

.delete-deck {
    color: var(--danger);
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1.05rem;
    padding: 0.25rem 0.5rem;
}

.deck-checkbox,
.category-checkbox {
    width: 18px;
    height: 18px;
    cursor: pointer;
    flex-shrink: 0;
}

/* Deck Folder Structure */
.deck-folder {
    background-color: var(--surface-color);
    margin-bottom: 0.5rem;
    border-radius: 6px;
    box-shadow: 0 1px 3px var(--shadow-color);
    overflow: hidden;
}

.deck-folder-header {
    display: flex;
    align-items: center;
    padding: 0.6rem 0.5rem;
    gap: 0.4rem;
    cursor: pointer;
    user-select: none;
}

.deck-folder-header:hover {
    background-color: var(--hover-bg, rgba(0, 0, 0, 0.04));
}

.deck-chevron {
    font-size: 0.7rem;
    transition: transform 0.2s ease;
    color: var(--text-muted, #888);
    flex-shrink: 0;
    width: 1rem;
    text-align: center;
}

.deck-folder.expanded .deck-chevron {
    transform: rotate(90deg);
}

.deck-folder-icon {
    font-size: 1.05rem;
    flex-shrink: 0;
}

.deck-folder-header .deck-title {
    flex: 1;
    font-weight: 500;
    color: var(--primary);
    cursor: pointer;
}

.deck-card-count {
    font-size: 1.05rem;
    color: var(--text-muted, #888);
    margin-left: 0.25rem;
}

.deck-categories {
    display: none;
    padding: 0.25rem 0.5rem 0.5rem 2.4rem;
    border-top: 1px solid var(--input-border);
    background-color: var(--bg-color);
}

.deck-folder.expanded .deck-categories {
    display: block;
}

.category-item {
    display: flex;
    align-items: center;
    padding: 0.3rem 0;
    gap: 0.4rem;
    font-size: 1.05rem;
}

.category-item label {
    cursor: pointer;
    color: var(--text-color);
    display: flex;
    align-items: center;
    gap: 0.3rem;
}

.category-item .category-icon {
    font-size: 0.85rem;
}

.category-count {
    font-size: 0.75rem;
    color: var(--text-muted, #888);
}

/* Flip Card Animation Styles */
.card-container {
    perspective: 1000px;
    margin-bottom: 1rem;
    min-height: 350px;
    height: calc(100vh - 280px);
    /* Fill available space */
    overflow: hidden;
    position: relative;
}

.card {
    position: relative;
    width: 100%;
    height: 100%;
    min-height: 350px;
    text-align: center;
    transition: transform 0.8s;
    transform-style: preserve-3d;
    will-change: transform;
}

.card.flipped {
    transform: rotateY(180deg);
}

/* Fly-in animation for new cards */
.card.fly-in-bottom {
    animation: flyInBottom 0.6s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
    transition: none; /* Disable transition during animation to prevent twitching */
}

@keyframes flyInBottom {
    from {
        transform: translateY(50px) rotateY(0deg);
        opacity: 0;
    }
    to {
        transform: translateY(0) rotateY(0deg);
        opacity: 1;
    }
}

.card-front,
.card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: 8px;
    box-shadow: 0 2px 4px var(--shadow-color);
    padding: 1rem;
    box-sizing: border-box;
    background-color: var(--surface-color);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    top: 0;
    left: 0;
    transition: opacity 0.4s ease;
}

.card-front {
    z-index: 2;
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
}

.card.flipped .card-front {
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
}

.card-back {
    transform: rotateY(180deg);
    z-index: 1;
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
}

.card.flipped .card-back {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
    z-index: 2;
}

.card-content {
    flex: 1;
    margin-bottom: 0.75rem;
    font-size: 1.05rem;
    overflow-y: auto;
    max-height: 100%;
}

.question {
    font-weight: bold;
    font-size: 1.2rem;
    color: var(--primary);
    margin-bottom: 0.75rem;
}

.answer {
    padding: 0.75rem;
    background-color: var(--light);
    border-left: 4px solid var(--primary);
    margin-top: 0.5rem;
    text-align: left;
}

/* User answer input styling */
.user-answer-input {
    width: 90%;
    padding: 0.75rem;
    margin: 1rem 0;
    border: 1px solid var(--input-border);
    border-radius: 4px;
    font-size: 1.05rem;
    background-color: var(--input-bg);
    color: var(--text-color);
    transition: border-color 0.15s ease-in-out;
}

.user-answer-input:focus {
    border-color: var(--primary);
    outline: 0;
    box-shadow: 0 0 0 0.2rem rgba(74, 111, 165, 0.25);
}

.user-answer-display {
    padding: 0.75rem;
    margin-top: 0.5rem;
    background-color: var(--cards-highlight-bg);
    border-left: 4px solid var(--cards-highlight-border);
    text-align: left;
    border-radius: 4px;
}

/* Multiple Choice Options Styling */
.options-container {
    display: flex;
    flex-direction: column;
    width: 90%;
    margin: 1rem auto;
    gap: 0.3rem;
}

.option-item {
    position: relative;
    padding: 0.3rem;
    border: 2px solid var(--input-border);
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    text-align: left;
}

.option-item:hover {
    border-color: var(--primary);
    background-color: var(--cards-hover-bg);
}

.option-item.selected {
    border-color: var(--primary);
    background-color: rgba(74, 111, 165, 0.1);
}

.option-item.correct {
    border-color: var(--success);
    background-color: rgba(40, 167, 69, 0.1);
}

.option-item.incorrect {
    border-color: var(--danger);
    background-color: rgba(220, 53, 69, 0.1);
}

/* Multiple Choice Feedback Styling */
.option-item.mc-correct-selected {
    background-color: var(--success-bg);
    border-color: var(--success);
    border-left-width: 4px;
}

.option-item.mc-correct-selected .option-checkbox {
    accent-color: var(--success);
}

.option-item.mc-incorrect-selected {
    background-color: var(--danger-bg);
    border-color: var(--danger);
    border-left-width: 4px;
}

.option-item.mc-incorrect-selected .option-checkbox {
    accent-color: var(--danger);
}

.option-item.mc-missed {
    background-color: var(--warning-bg);
    border-color: var(--warning);
    border-left-width: 4px;
}

.option-item.mc-missed .option-checkbox {
    accent-color: var(--warning);
}

.option-item.mc-neutral {
    background-color: var(--surface-secondary);
    border-color: var(--border-color);
    opacity: 0.7;
}

.option-checkbox {
    margin-right: 0.75rem;
    width: 18px;
    height: 18px;
}

.selected-options-display {
    padding: 0.75rem;
    margin-top: 0.5rem;
    background-color: var(--cards-highlight-bg);
    border-left: 4px solid var(--cards-highlight-border);
    text-align: left;
    border-radius: 4px;
}

.controls {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 0.5rem;
    width: 100%;
}

.btn {
    padding: 0.4rem 0.8rem;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-weight: 500;
    transition: all 0.3s;
    flex: 1;
    min-width: 80px;
    font-size: 1.05rem;
}

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

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

.btn-primary:disabled,
.btn-primary[disabled] {
    background-color: var(--disabled-bg);
    color: var(--text-muted);
    cursor: not-allowed;
    opacity: 0.6;
}

.btn-success {
    background-color: var(--success);
    color: white;
}

.btn-success:hover {
    background-color: #218838;
}

.btn-danger {
    background-color: var(--danger);
    color: white;
}

.btn-danger:hover {
    background-color: #c82333;
}

.btn-secondary {
    background-color: var(--btn-secondary-bg);
    color: white;
}

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

.stats {
    display: flex;
    justify-content: space-around;
    margin: 0 0 0.5rem 0;
    padding: 0 0 0.5rem 0;
    background-color: var(--surface-color);
    border-radius: 0 0 8px 8px;
    box-shadow: 0 2px 4px var(--shadow-color);
}

.stat-item {
    text-align: center;
}

.stat-value {
    font-size: 1.15rem;
    font-weight: bold;
    color: var(--primary);
}

.stat-label {
    font-size: 1.05rem;
    color: var(--text-muted);
}

.progress-bar {
    height: 6px;
    background-color: var(--progress-track);
    border-radius: 4px;
    margin: 0.5rem 0;
    overflow: hidden;
}

.progress {
    height: 100%;
    background-color: var(--primary);
    width: 0%;
    transition: width 0.3s ease;
}

.feedback {
    font-size: 1.05rem;
    text-align: center;
    margin-top: 1rem;
    color: var(--text-muted);
}

.error-message {
    color: var(--danger);
    text-align: center;
    margin: 1rem 0;
}

.hidden {
    display: none;
}

#sample-json {
    margin-top: 1rem;
    padding: 0.75rem;
    background-color: var(--surface-secondary);
    border-radius: 4px;
    border: 1px solid var(--border-color);
    font-family: monospace;
    font-size: 0.9rem;
    text-align: left;
}

#sample-json pre {
    margin: 0;
    padding: 0;
    white-space: pre;
    overflow-x: auto;
    text-align: left;
}

#sample-json code {
    font-family: 'Courier New', Courier, monospace;
    font-size: 0.9rem;
}

.json-toggle {
    margin-top: 0.5rem;
    font-size: 1.05rem;
    color: var(--primary);
    cursor: pointer;
    text-decoration: underline;
}

@media (max-width: 600px) {
    .container {
        width: 95%;
        margin: 0.5rem auto;
    }

    .controls {
        gap: 0.3rem;
    }

    .btn {
        padding: 0.3rem 0.6rem;
        font-size: 1.05rem;
    }

    .card-container {
        min-height: 330px;
    }

    .card {
        min-height: 330px;
    }

    .stats {
        padding: 0.4rem 0.2rem;
    }

    .stat-value {
        font-size: 1.1rem;
    }

    .stat-label {
        font-size: 1.05rem;
    }
}

/* ============================================================================
   UX Enhancements
   ============================================================================ */

/* Study Mode Select */
.study-mode-select {
    padding: 0.5rem 0.75rem;
    border: 2px solid var(--input-border);
    border-radius: 6px;
    font-size: 1.05rem;
    background-color: var(--input-bg);
    color: var(--text-color);
    cursor: pointer;
    transition: border-color 0.3s;
    min-width: 200px;
}

.study-mode-select:hover {
    border-color: var(--primary);
}

.study-mode-select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
}

/* Drop Zone */
.drop-zone {
    margin-top: 0.75rem;
    border: 2px dashed var(--text-muted, #aaa);
    border-radius: 8px;
    padding: 1.5rem 1rem;
    text-align: center;
    cursor: pointer;
    transition: all 0.2s ease;
    background-color: var(--surface-color, #fff);
}

.drop-zone:hover {
    border-color: var(--primary);
    background-color: var(--cards-hover-bg, #f0f5ff);
}

.drop-zone.drag-over {
    border-color: var(--primary);
    background-color: var(--cards-highlight-bg, #e9f2ff);
    border-style: solid;
    box-shadow: 0 0 0 3px rgba(74, 111, 165, 0.15);
}

.drop-zone-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.3rem;
    pointer-events: none;
}

.drop-zone-icon {
    font-size: 1.75rem;
    line-height: 1;
}

.drop-zone-text {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--dark, #343a40);
}

.drop-zone-hint {
    font-size: 0.85rem;
    color: var(--text-muted, #888);
}

/* Upload Actions (JSON sample link) */
.upload-actions {
    text-align: center;
    margin: 0.3rem 0 0;
}

/* Saved Decks Header */
.saved-decks-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 0.5rem;
}

.saved-decks-header h3 {
    margin: 0;
}

.saved-decks-header .btn {
    flex: none;
    font-size: 0.85rem;
    padding: 0.3rem 0.65rem;
    white-space: nowrap;
}

/* SR Stats Dashboard */
#sr-stats-dashboard {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
    margin-bottom: 0.75rem;
    align-items: center;
}

.sr-stat-card {
    background-color: var(--surface-color);
    border-radius: 4px;
    padding: 0.25rem 0.5rem;
    box-shadow: 0 1px 2px var(--shadow-color);
    font-size: 1.05rem;
    color: var(--text-muted, #888);
}

.sr-stat-value {
    font-weight: 700;
    color: var(--primary);
}

.sr-bucket-bar {
    display: flex;
    height: 10px;
    border-radius: 5px;
    overflow: hidden;
    background-color: var(--input-border);
    margin-bottom: 0.25rem;
    flex-basis: 100%;
}

.sr-bucket-bar-segment {
    height: 100%;
    transition: width 0.3s ease;
}

.sr-bucket-bar-legend {
    display: flex;
    flex-wrap: wrap;
    gap: 0.2rem 0.75rem;
    font-size: 0.7rem;
    color: var(--text-muted, #888);
    flex-basis: 100%;
}

.sr-bucket-bar-legend span::before {
    content: '';
    display: inline-block;
    width: 8px;
    height: 8px;
    border-radius: 2px;
    margin-right: 0.25rem;
    vertical-align: middle;
    background-color: var(--legend-color);
}

/* Undo Button */
#undo-btn {
    margin-right: auto;
}

#undo-btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

.btn.btn-sm {
    padding: 0.25rem 0.55rem;
    font-size: 0.85rem;
}

/* Back link in page header */
.back-link {
    color: var(--primary);
    text-decoration: none;
    font-size: 1.5rem;
    font-weight: 500;
    line-height: 1;
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    transition: background-color 0.2s;
    flex-shrink: 0;
}

.back-link:hover {
    background-color: var(--light);
}

/* Deck Search */
.deck-search-container {
    margin-bottom: 1rem;
}

.deck-search-input {
    width: 100%;
    padding: 0.75rem;
    font-size: 1.05rem;
    border: 2px solid var(--input-border);
    background-color: var(--input-bg);
    color: var(--text-color);
    border-radius: 6px;
    box-sizing: border-box;
    transition: border-color 0.3s;
}

.deck-search-input:focus {
    outline: none;
    border-color: var(--primary);
}

/* Confetti Animation Styles */
#confetti-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    overflow: hidden;
    z-index: 9999;
}

.confetti-piece {
    position: absolute;
    width: 12px;
    height: 12px;
    will-change: transform, opacity;
}

@keyframes confetti-fall {
    0% {
        transform: translateY(0) translateX(0) rotateZ(0deg);
        opacity: 1;
    }
    70% {
        opacity: 1;
    }
    100% {
        transform: translateY(60vh) translateX(var(--confetti-x, 0px))
            rotateZ(var(--confetti-rotate, 720deg));
        opacity: 0;
    }
}

/* Responsive adjustments */
@media (max-width: 768px) {
    .header {
        flex-direction: column;
        align-items: stretch;
        gap: 0.75rem;
        padding: 0.75rem;
    }

    .header h1 {
        font-size: 1.1rem;
    }

    .header p {
        font-size: 1.05rem;
    }

    .study-mode-select {
        width: 100%;
        min-width: unset;
    }

    .deck-folder-header {
        padding: 0.7rem 0.5rem;
        gap: 0.35rem;
    }

    .deck-folder-header .deck-title {
        font-size: 1.05rem;
        word-break: break-word;
        min-width: 0;
    }

    .deck-card-count {
        font-size: 0.85rem;
        white-space: nowrap;
    }

    .deck-categories {
        padding-left: 1.6rem;
        padding-right: 0.3rem;
    }

    .category-item {
        padding: 0.4rem 0;
    }

    .category-item label {
        font-size: 1.05rem;
    }
}

/* ============================================================================
   Explanation Styles
   ============================================================================ */

/* Text answer explanation container */
#text-explanation-container {
    margin-top: 1rem;
}

.explanation-box {
    background-color: var(--explanation-bg);
    border: 2px solid var(--explanation-border);
    border-radius: 8px;
    padding: 0.75rem;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.explanation-box:hover {
    background-color: var(--explanation-hover-bg);
    border-color: #1976d2;
    transform: translateY(-1px);
    box-shadow: 0 2px 8px rgba(33, 150, 243, 0.2);
}

.explanation-icon {
    font-size: 1.5rem;
    flex-shrink: 0;
    animation: pulse 2s infinite;
}

@keyframes pulse {
    0%,
    100% {
        transform: scale(1);
    }
    50% {
        transform: scale(1.1);
    }
}

.explanation-label {
    font-weight: 600;
    color: var(--explanation-text);
    flex-grow: 1;
}

.explanation-content {
    width: 100%;
    margin-top: 0.75rem;
    padding-top: 0.75rem;
    border-top: 1px solid var(--explanation-border-light);
    color: var(--explanation-content-text);
    line-height: 1.5;
    animation: slideDown 0.3s ease;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* MC option explanation indicator */
.option-explanation-indicator {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 24px;
    height: 24px;
    margin-left: 0.5rem;
    background-color: var(--explanation-border);
    color: white;
    border-radius: 50%;
    cursor: pointer;
    font-size: 0.85rem;
    font-weight: bold;
    transition: all 0.2s ease;
    position: relative;
}

.option-explanation-indicator:hover {
    background-color: var(--explanation-text);
    transform: scale(1.15);
}

.option-explanation-indicator::before {
    content: 'ℹ';
}

/* Tooltip for option explanations */
.option-explanation-tooltip {
    display: none;
    position: fixed;
    padding: 0.75rem;
    background-color: var(--tooltip-bg);
    color: white;
    border-radius: 6px;
    font-size: 1.05rem;
    line-height: 1.4;
    white-space: normal;
    min-width: 200px;
    max-width: min(300px, calc(100vw - 2rem));
    z-index: 10000;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
    animation: fadeIn 0.2s ease;
    pointer-events: auto;
}

/* Arrow pointing down (tooltip is above) */
.option-explanation-tooltip[data-arrow='down']::after {
    content: '';
    position: absolute;
    top: 100%;
    left: 12px;
    border: 6px solid transparent;
    border-top-color: var(--tooltip-bg);
}

/* Arrow pointing up (tooltip is below) */
.option-explanation-tooltip[data-arrow='up']::after {
    content: '';
    position: absolute;
    bottom: 100%;
    left: 12px;
    border: 6px solid transparent;
    border-bottom-color: var(--tooltip-bg);
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

/* Ensure option items have relative positioning for tooltip positioning */
.option-item {
    position: relative;
}

/* ============================================================================
   Spaced Repetition Manager Styles
   ============================================================================ */

.sr-manager-btn {
    margin: 0 0 0 0.5rem;
    padding: 0.5rem 0.75rem;
    font-size: 1.05rem;
    white-space: nowrap;
    min-width: 130px;
}

.sr-manager-btn.active {
    background-color: var(--primary);
    color: white;
}

#spaced-repetition-manager-container {
    background: var(--surface-color);
    padding: 1.5rem;
    border-radius: 8px;
    box-shadow: 0 2px 8px var(--shadow-color);
    margin-bottom: 1rem;
}

#spaced-repetition-manager-container h3 {
    margin-top: 0;
    color: var(--primary);
}

.sr-info {
    color: var(--text-muted);
    font-size: 1.05rem;
    margin-bottom: 1rem;
}

#sr-bucket-selection-controls {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
    margin-bottom: 1.5rem;
}

#sr-buckets-display {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.sr-bucket {
    background: var(--surface-secondary);
    border: 2px solid var(--border-color);
    border-radius: 8px;
    overflow: hidden;
}

.sr-bucket.selected {
    border-color: var(--primary);
    box-shadow: 0 0 0 2px rgba(74, 111, 165, 0.2);
}

.sr-bucket-header {
    padding: 0.75rem 1rem;
    background: linear-gradient(135deg, var(--sr-gradient-start) 0%, var(--sr-gradient-end) 100%);
    color: white;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    user-select: none;
}

.sr-bucket-header:hover {
    background: linear-gradient(
        135deg,
        var(--sr-gradient-hover-start) 0%,
        var(--sr-gradient-hover-end) 100%
    );
}

.sr-bucket-info {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.sr-bucket-title {
    font-weight: 600;
    font-size: 1.05rem;
}

.sr-bucket-count {
    background: rgba(255, 255, 255, 0.2);
    padding: 0.25rem 0.75rem;
    border-radius: 12px;
    font-size: 1.05rem;
}

.sr-bucket-interval {
    font-size: 1.05rem;
    opacity: 0.9;
}

.sr-bucket-checkbox {
    width: 20px;
    height: 20px;
    cursor: pointer;
}

.sr-bucket-cards {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
}

.sr-bucket-cards.expanded {
    max-height: 1000px;
    overflow-y: auto;
}

.sr-card-item {
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: background 0.2s;
}

.sr-card-item:hover {
    background: var(--surface-secondary);
}

.sr-card-item:last-child {
    border-bottom: none;
}

.sr-card-question {
    flex: 1;
    font-weight: 500;
    margin-right: 1rem;
}

.sr-card-meta {
    display: flex;
    align-items: center;
    gap: 1rem;
    font-size: 1.05rem;
    color: var(--text-muted);
}

.sr-card-next-review {
    white-space: nowrap;
}

.sr-card-actions {
    display: flex;
    gap: 0.5rem;
}

.sr-card-actions button {
    padding: 0.25rem 0.5rem;
    font-size: 1.05rem;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.2s;
}

.sr-move-btn {
    background: var(--sr-info-color);
    color: white;
}

.sr-move-btn:hover {
    background: var(--sr-info-hover);
}

.sr-delete-btn {
    background: #dc3545;
    color: white;
}

.sr-delete-btn:hover {
    background: #c82333;
}

.sr-empty-message {
    padding: 2rem;
    text-align: center;
    color: var(--text-muted);
    font-style: italic;
}

/* Update Notification Banner */
#update-notification {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    background: linear-gradient(135deg, var(--sr-gradient-start) 0%, var(--sr-gradient-end) 100%);
    color: white;
    padding: 0.75rem 1.25rem;
    border-radius: 8px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
    display: flex;
    align-items: center;
    gap: 1rem;
    z-index: 10000;
    animation: slideUp 0.3s ease;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateX(-50%) translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateX(-50%) translateY(0);
    }
}

#update-notification span {
    font-weight: 500;
}

#update-notification button {
    background: var(--surface-color);
    color: var(--secondary);
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    cursor: pointer;
    font-weight: 600;
    transition: all 0.2s;
}

#update-notification button:hover {
    background: var(--surface-secondary);
    transform: scale(1.02);
}

#update-notification button.dismiss {
    background: transparent;
    color: white;
    padding: 0.25rem 0.5rem;
    font-size: 1.2rem;
    opacity: 0.8;
}

#update-notification button.dismiss:hover {
    opacity: 1;
    background: rgba(255, 255, 255, 0.1);
}

/* SR card review status colors */
.sr-overdue {
    color: var(--danger);
}
.sr-on-time {
    color: var(--success);
}

/* ============================================================================
   Keyboard Focus Styles
   ============================================================================ */

/* Remove default outline for mouse clicks, keep for keyboard */
:focus:not(:focus-visible) {
    outline: none;
}

/* Universal keyboard focus ring */
:focus-visible {
    outline: 3px solid var(--primary);
    outline-offset: 2px;
}

/* Buttons */
.btn:focus-visible {
    outline: 3px solid var(--primary);
    outline-offset: 2px;
    box-shadow: 0 0 0 4px rgba(74, 111, 165, 0.3);
}

.btn-success:focus-visible {
    outline-color: var(--success);
    box-shadow: 0 0 0 4px rgba(40, 167, 69, 0.3);
}

.btn-danger:focus-visible {
    outline-color: var(--danger);
    box-shadow: 0 0 0 4px rgba(220, 53, 69, 0.3);
}

/* MC option items */
.option-item:focus-visible {
    outline: 3px solid var(--primary);
    outline-offset: -1px;
    border-color: var(--primary);
    background-color: var(--cards-hover-bg);
}

/* Theme toggle */
.theme-toggle:focus-visible {
    outline: 3px solid var(--primary);
    outline-offset: 2px;
}

/* Explanation box */
.explanation-box:focus-visible {
    outline: 3px solid var(--explanation-border);
    outline-offset: 2px;
}

/* Upload label (acts as button) */
#upload-label:focus-visible {
    outline: 3px solid var(--primary);
    outline-offset: 2px;
    box-shadow: 0 0 0 4px rgba(74, 111, 165, 0.3);
}

/* Delete deck button */
.delete-deck:focus-visible {
    outline: 2px solid var(--danger);
    outline-offset: 2px;
}

/* JSON toggle link */
.json-toggle:focus-visible {
    outline: 2px solid var(--primary);
    outline-offset: 2px;
    border-radius: 2px;
}

/* Keyboard shortcut hint kbd styling */
.keyboard-hint kbd {
    display: inline-block;
    padding: 0.1rem 0.4rem;
    font-size: 0.8rem;
    background: var(--surface-secondary);
    border: 1px solid var(--border-color);
    border-radius: 3px;
    font-family: inherit;
    margin-right: 0.25rem;
}

/* Keyboard hints floating panel */
.keyboard-hints {
    position: fixed;
    bottom: calc(1rem + 44px + 0.75rem);
    right: 1rem;
    z-index: 100;
}

.keyboard-hints-toggle {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    border: 2px solid rgba(128, 128, 128, 0.3);
    background-color: rgba(255, 255, 255, 0.9);
    cursor: pointer;
    font-size: 1.3rem;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
    transition:
        background-color 0.3s,
        transform 0.2s,
        opacity 0.2s;
    opacity: 0.75;
    color: var(--text-color);
    padding: 0;
    line-height: 1;
}

.keyboard-hints-toggle.pulse {
    animation: hintsPulse 1.5s ease-in-out 3;
}

@keyframes hintsPulse {
    0%,
    100% {
        transform: scale(1);
        opacity: 0.75;
    }
    50% {
        transform: scale(1.15);
        opacity: 1;
        box-shadow: 0 2px 12px rgba(74, 111, 165, 0.4);
    }
}

.keyboard-hints-toggle:hover,
.keyboard-hints-toggle:focus-visible {
    opacity: 1;
    transform: scale(1.1);
}

[data-theme='dark'] .keyboard-hints-toggle {
    background-color: rgba(50, 50, 50, 0.9);
    border-color: rgba(128, 128, 128, 0.4);
}

.keyboard-hints-panel {
    position: absolute;
    bottom: 3.25rem;
    right: 0;
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.75rem;
    box-shadow: 0 4px 12px var(--shadow-color);
    min-width: 240px;
    font-size: 1.05rem;
}

.keyboard-hints-title {
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--primary);
}

.keyboard-hint {
    padding: 0.2rem 0;
    color: var(--text-color);
}

/* ============================================================================
   Dark Mode Overrides
   ============================================================================ */
[data-theme='dark'] {
    --primary: #6b9fd4;
    --secondary: #4a8ab8;
    --light: #2a2a3c;
    --dark: #e0e0e0;
    --success: #4caf50;
    --danger: #ef5350;
    --warning: #ffca28;

    --cards-highlight-bg: rgba(107, 159, 212, 0.15);
    --cards-highlight-border: rgba(107, 159, 212, 0.5);
    --cards-hover-bg: rgba(107, 159, 212, 0.1);
    --success-bg: rgba(76, 175, 80, 0.2);
    --danger-bg: rgba(239, 83, 80, 0.2);
    --warning-bg: rgba(255, 202, 40, 0.2);
    --disabled-bg: #3a3a4c;
    --progress-track: #3a3a4c;
    --explanation-bg: rgba(107, 159, 212, 0.15);
    --explanation-hover-bg: rgba(107, 159, 212, 0.25);
    --explanation-border: #6b9fd4;
    --explanation-border-light: rgba(107, 159, 212, 0.3);
    --explanation-text: #8bbae8;
    --explanation-content-text: #a0c8f0;
    --tooltip-bg: #2a4a6b;
    --btn-secondary-bg: #5a5a6e;
    --btn-secondary-hover: #6a6a7e;
    --sr-gradient-start: #3a6a9e;
    --sr-gradient-end: #2a5a88;
    --sr-gradient-hover-start: #4a7aae;
    --sr-gradient-hover-end: #3a6a98;
    --sr-info-color: #20b2cc;
    --sr-info-hover: #18a2bc;
}

[data-theme='dark'] .btn-success:hover {
    background-color: #43a047;
}

[data-theme='dark'] .btn-danger:hover {
    background-color: #e53935;
}

[data-theme='dark'] .sr-delete-btn {
    background: var(--danger);
}

[data-theme='dark'] .sr-delete-btn:hover {
    background: #e53935;
}

[data-theme='dark'] .btn:focus-visible {
    box-shadow: 0 0 0 4px rgba(107, 159, 212, 0.3);
}

[data-theme='dark'] .btn-success:focus-visible {
    box-shadow: 0 0 0 4px rgba(76, 175, 80, 0.3);
}

[data-theme='dark'] .btn-danger:focus-visible {
    box-shadow: 0 0 0 4px rgba(239, 83, 80, 0.3);
}

/* ============================================================================
   Book View / Lesemodus
   ============================================================================ */

.book-view-toolbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.75rem 0;
    margin-bottom: 1rem;
    border-bottom: 2px solid var(--input-border);
    gap: 0.5rem;
}

.book-view-title {
    font-weight: 600;
    font-size: 1.05rem;
    color: var(--primary);
    text-align: center;
    flex: 1;
    min-width: 0;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.book-view-export-btns {
    display: flex;
    gap: 0.4rem;
    flex-shrink: 0;
}

.book-card {
    background-color: var(--surface-color);
    border-radius: 8px;
    padding: 1.25rem;
    margin-bottom: 1rem;
    box-shadow: 0 1px 4px var(--shadow-color);
    page-break-inside: avoid;
}

.book-card-number {
    font-size: 0.75rem;
    color: var(--text-muted, #888);
    margin-bottom: 0.4rem;
}

.book-card-question {
    font-weight: 600;
    font-size: 1.05rem;
    color: var(--text-color);
    margin-bottom: 0.75rem;
    line-height: 1.4;
}

.book-card-answer {
    color: var(--text-color);
    padding: 0.6rem 0.75rem;
    background-color: var(--bg-color);
    border-left: 3px solid var(--success, #27ae60);
    border-radius: 0 4px 4px 0;
    margin-bottom: 0.5rem;
    line-height: 1.4;
}

.book-card-explanation {
    color: var(--text-muted, #888);
    font-size: 1.05rem;
    padding: 0.5rem 0.75rem;
    background-color: var(--bg-color);
    border-left: 3px solid var(--primary);
    border-radius: 0 4px 4px 0;
    margin-top: 0.5rem;
    line-height: 1.4;
}

.book-card-sr-badge {
    font-size: 1.05rem;
    color: var(--text-muted, #888);
    background-color: var(--bg-color);
    border: 1px solid var(--input-border);
    border-radius: 4px;
    padding: 0.3rem 0.6rem;
    margin-bottom: 0.6rem;
    display: inline-block;
}

.book-sr-overdue {
    color: var(--danger);
    border-color: var(--danger);
}

.book-sr-good {
    color: var(--success, #27ae60);
    border-color: var(--success, #27ae60);
}

.book-section-separator {
    text-align: center;
    font-weight: 600;
    color: var(--text-muted, #888);
    padding: 1rem 0 0.5rem;
    margin: 0.5rem 0;
    border-top: 2px solid var(--input-border);
    font-size: 1.05rem;
}

.book-card-source {
    font-size: 0.75rem;
    color: var(--text-muted, #888);
    margin-top: 0.5rem;
    text-align: right;
}

.book-card-options {
    margin-bottom: 0.5rem;
}

.book-option {
    padding: 0.3rem 0.5rem;
    margin: 0.25rem 0;
    border-radius: 4px;
    font-size: 1.05rem;
    display: flex;
    align-items: baseline;
    gap: 0.4rem;
}

.book-option-correct {
    background-color: rgba(39, 174, 96, 0.12);
    border-left: 3px solid var(--success, #27ae60);
}

.book-option-wrong {
    opacity: 0.65;
}

.book-option-explanation {
    font-size: 1.05rem;
    color: var(--text-muted, #888);
    margin-left: 1.2rem;
    margin-bottom: 0.3rem;
    padding: 0.3rem 0.6rem;
    border-left: 3px solid var(--primary);
    background-color: var(--bg-color);
    border-radius: 0 4px 4px 0;
    line-height: 1.4;
}

.sr-bucket-book-btn {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1.05rem;
    padding: 0.25rem 0.4rem;
    border-radius: 4px;
}

.sr-bucket-book-btn:hover {
    background-color: rgba(0, 0, 0, 0.08);
}

@media (max-width: 768px) {
    .book-view-toolbar {
        flex-wrap: wrap;
    }

    .book-view-title {
        order: -1;
        flex-basis: 100%;
        white-space: normal;
        margin-bottom: 0.5rem;
    }

    .book-card {
        padding: 1rem;
    }
}

/* Print Styles */
@media print {
    body {
        background: white !important;
        color: black !important;
    }

    .container {
        width: 100% !important;
        max-width: none !important;
        margin: 0 !important;
        padding: 0 !important;
        box-shadow: none !important;
    }

    .header,
    .book-view-toolbar,
    #confetti-container {
        display: none !important;
    }

    #book-view {
        display: block !important;
    }

    .book-card {
        box-shadow: none !important;
        border: 1px solid #ddd;
        break-inside: avoid;
    }

    .book-card-answer {
        background-color: #f5f5f5 !important;
    }

    .book-card-explanation {
        background-color: #f5f5f5 !important;
    }
}