/* ==========================================================================
   4. Spaced Repetition (SRS), 3D Flashcards, Quiz, Typing & Heatmap
   ========================================================================== */

/* SRS View Structure */
.srs-view {
    min-height: calc(100vh - 65px);
    display: flex;
    flex-direction: column;
    background: radial-gradient(circle at 50% 15%, rgba(56, 189, 248, 0.07), transparent 60%);
}

.srs-topbar {
    background-color: var(--bg-surface);
    border-bottom: 1px solid var(--border-color);
    padding: 12px 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
}

.srs-topbar-left {
    display: flex;
    align-items: center;
    gap: 16px;
}

.srs-mode-switch {
    display: flex;
    background-color: var(--bg-main);
    padding: 3px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
}

.srs-tab {
    background: transparent;
    border: none;
    color: var(--text-muted);
    padding: 6px 14px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.srs-tab:hover {
    color: var(--text-main);
}

.srs-tab.active {
    background-color: var(--primary);
    color: #0f172a;
    font-weight: 700;
    box-shadow: var(--shadow-sm);
}

.srs-topbar-center {
    flex: 1;
    max-width: 380px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
}

.srs-progress-container {
    width: 100%;
    height: 7px;
    background-color: var(--bg-main);
    border-radius: var(--radius-full);
    overflow: hidden;
    border: 1px solid var(--border-color);
}

.srs-progress-fill {
    height: 100%;
    background: linear-gradient(90deg, #0284c7, #38bdf8);
    border-radius: var(--radius-full);
    transition: width 0.3s ease;
}

.srs-counter {
    font-size: 11px;
    font-weight: 600;
    color: var(--text-dim);
}

.srs-topbar-right {
    display: flex;
    align-items: center;
}

.srs-arena {
    flex: 1;
    max-width: 720px;
    width: 100%;
    margin: 0 auto;
    padding: 32px 16px;
    display: flex;
    flex-direction: column;
    justify-content: center;
}

.srs-state-box {
    text-align: center;
    padding: 64px 24px;
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 16px;
}

.srs-big-icon {
    font-size: 56px;
}

.srs-empty-buttons {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
    justify-content: center;
    margin-top: 12px;
}

/* Flashcard 3D Card Flip */
.srs-mode-container {
    display: flex;
    flex-direction: column;
    gap: 20px;
    animation: fadeIn 0.25s ease-out;
}

.flashcard-wrapper {
    perspective: 1400px;
    min-height: 380px;
    cursor: pointer;
    user-select: none;
}

.flashcard-inner {
    position: relative;
    width: 100%;
    min-height: 380px;
    transform-style: preserve-3d;
    transition: transform 0.48s cubic-bezier(0.4, 0, 0.2, 1);
}

.flashcard-inner.is-flipped {
    transform: rotateY(180deg);
}

.flashcard-face {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    min-height: 380px;
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 28px 32px;
    box-shadow: var(--shadow-lg);
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

.flashcard-front {
    transform: rotateY(0deg);
}

.flashcard-back {
    transform: rotateY(180deg);
    background: radial-gradient(circle at top right, rgba(56, 189, 248, 0.06), var(--bg-card) 70%);
}

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

.fc-dir-badge {
    font-size: 11px;
    font-weight: 700;
    letter-spacing: 0.5px;
    color: var(--primary);
    background-color: var(--primary-dim);
    padding: 3px 10px;
    border-radius: var(--radius-full);
}

.fc-pos-badge {
    font-size: 11px;
    color: var(--text-dim);
    background-color: var(--bg-surface-hover);
    padding: 2px 8px;
    border-radius: 4px;
}

.fc-center {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    gap: 16px;
    padding: 20px 0;
}

.fc-main-term {
    font-size: 38px;
    font-weight: 800;
    letter-spacing: -0.5px;
    color: var(--text-main);
}

.fc-phonetic-row {
    display: flex;
    align-items: center;
    gap: 10px;
}

.audio-round-btn {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background-color: var(--primary-dim);
    border: 1px solid var(--primary);
    color: var(--primary);
    font-size: 16px;
    cursor: pointer;
    transition: var(--transition);
}

.audio-round-btn:hover {
    background-color: var(--primary);
    color: #0f172a;
    transform: scale(1.08);
}

.fc-hint-wrapper {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    max-width: 500px;
}

.fc-hint-content {
    font-size: 14px;
    font-style: italic;
    color: var(--text-muted);
    background-color: var(--bg-main);
    padding: 10px 16px;
    border-radius: var(--radius-sm);
    border-left: 3px solid var(--primary);
}

.fc-footer-hint {
    text-align: center;
    font-size: 12px;
    color: var(--text-dim);
}

.fc-footer-hint kbd {
    background-color: var(--bg-surface-hover);
    border: 1px solid var(--border-color);
    padding: 2px 6px;
    border-radius: 4px;
    font-family: monospace;
}

/* Flashcard Back */
.fc-back-content {
    display: flex;
    flex-direction: column;
    gap: 14px;
    height: 100%;
}

.fc-back-top {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 8px;
}

.fc-back-term {
    font-size: 24px;
    font-weight: 700;
    color: var(--text-main);
}

.fc-back-translation {
    font-size: 22px;
    font-weight: 700;
    color: var(--primary);
}

.fc-back-detail-box {
    background-color: var(--bg-main);
    border-radius: var(--radius-sm);
    padding: 10px 14px;
    border-left: 2px solid var(--border-color);
}

.detail-label {
    font-size: 10px;
    font-weight: 700;
    text-transform: uppercase;
    color: var(--text-dim);
    letter-spacing: 0.5px;
    margin-bottom: 2px;
    display: block;
}

.detail-text {
    font-size: 13px;
    color: var(--text-main);
    line-height: 1.4;
}

.fc-flip-btn-wrap {
    display: none;
}

/* SRS Rating Bar */
.srs-rating-bar {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
    margin-top: 8px;
    animation: fadeIn 0.2s ease-out;
}

.btn-rate {
    padding: 12px 10px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background-color: var(--bg-surface);
    cursor: pointer;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2px;
    transition: var(--transition);
}

.btn-rate .rate-key {
    font-size: 11px;
    font-family: monospace;
    opacity: 0.7;
}

.btn-rate .rate-name {
    font-size: 15px;
    font-weight: 700;
}

.btn-rate .rate-time {
    font-size: 11px;
    opacity: 0.75;
}

/* Rating variants */
.btn-rate-1 {
    border-color: rgba(239, 68, 68, 0.4);
    color: #f87171;
}
.btn-rate-1:hover {
    background-color: rgba(239, 68, 68, 0.15);
    border-color: #ef4444;
}

.btn-rate-2 {
    border-color: rgba(245, 158, 11, 0.4);
    color: #fbbf24;
}
.btn-rate-2:hover {
    background-color: rgba(245, 158, 11, 0.15);
    border-color: #f59e0b;
}

.btn-rate-3 {
    border-color: rgba(56, 189, 248, 0.4);
    color: #38bdf8;
}
.btn-rate-3:hover {
    background-color: rgba(56, 189, 248, 0.15);
    border-color: #38bdf8;
}

.btn-rate-4 {
    border-color: rgba(16, 185, 129, 0.4);
    color: #34d399;
}
.btn-rate-4:hover {
    background-color: rgba(16, 185, 129, 0.15);
    border-color: #10b981;
}

/* Interactive Trainer Card (Cloze & Dictation) */
.trainer-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 32px;
    box-shadow: var(--shadow-lg);
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.trainer-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.mode-tag {
    font-size: 12px;
    font-weight: 700;
    color: var(--primary);
    background-color: var(--primary-dim);
    padding: 3px 12px;
    border-radius: var(--radius-full);
}

.trainer-pos {
    font-size: 12px;
    color: var(--text-dim);
}

.cloze-sentence-display {
    font-size: 20px;
    line-height: 1.6;
    color: var(--text-main);
    background-color: var(--bg-main);
    padding: 20px 24px;
    border-radius: var(--radius-md);
    border-left: 4px solid var(--primary);
}

.gap-placeholder {
    color: var(--primary);
    font-weight: 800;
    letter-spacing: 2px;
    border-bottom: 2px dashed var(--primary);
    padding: 0 4px;
}

.cloze-translation-hint {
    font-size: 14px;
    color: var(--text-muted);
}

.cloze-translation-hint strong {
    color: var(--text-main);
    margin-left: 6px;
}

.trainer-form {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.input-action-row {
    display: flex;
    gap: 10px;
}

.input-hero {
    font-size: 18px;
    padding: 12px 18px;
}

.trainer-feedback-box {
    padding: 14px 18px;
    border-radius: var(--radius-sm);
    font-size: 15px;
    font-weight: 600;
    animation: fadeIn 0.2s ease-out;
}

.trainer-feedback-box.correct {
    background-color: var(--success-dim);
    border: 1px solid var(--success);
    color: #34d399;
}

.trainer-feedback-box.incorrect {
    background-color: var(--danger-dim);
    border: 1px solid var(--danger);
    color: #fca5a5;
}

.trainer-revealed-details {
    background-color: var(--bg-main);
    border-radius: var(--radius-md);
    padding: 16px;
    display: flex;
    flex-direction: column;
    gap: 10px;
    border: 1px solid var(--border-color);
    animation: fadeIn 0.2s ease-out;
}

/* Audio Dictation Mode */
.dictation-hero {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 14px;
    padding: 16px 0;
}

.dictation-pulse-btn {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    background: linear-gradient(135deg, #0284c7, #38bdf8);
    border: none;
    color: #0f172a;
    font-size: 34px;
    cursor: pointer;
    box-shadow: 0 0 0 0 rgba(56, 189, 248, 0.4);
    animation: pulseAudio 2s infinite;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.dictation-pulse-btn:hover {
    transform: scale(1.08);
}

@keyframes pulseAudio {
    0% { box-shadow: 0 0 0 0 rgba(56, 189, 248, 0.6); }
    70% { box-shadow: 0 0 0 22px rgba(56, 189, 248, 0); }
    100% { box-shadow: 0 0 0 0 rgba(56, 189, 248, 0); }
}

.dictation-instructions {
    font-size: 14px;
    color: var(--text-muted);
}

.audio-replay-btn .kbd-sub {
    font-size: 10px;
    margin-left: 4px;
}

.dictation-hint-wrap {
    display: flex;
    align-items: center;
    gap: 10px;
}

.dictation-hint-text {
    font-size: 13px;
    color: var(--text-muted);
    font-style: italic;
}

/* Interactive Listening Comprehension Mode */
.listening-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 28px 32px;
    box-shadow: var(--shadow-lg);
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.listening-header-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 12px;
}

.listening-tag-wrap {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

.level-badge {
    font-size: 11px;
    font-weight: 700;
    padding: 2px 8px;
    border-radius: var(--radius-sm);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.level-badge.badge-a1 { background: rgba(59, 130, 246, 0.15); color: #60a5fa; border: 1px solid rgba(59, 130, 246, 0.3); }
.level-badge.badge-a2 { background: rgba(16, 185, 129, 0.15); color: #34d399; border: 1px solid rgba(16, 185, 129, 0.3); }
.level-badge.badge-b1 { background: rgba(245, 158, 11, 0.15); color: #fbbf24; border: 1px solid rgba(245, 158, 11, 0.3); }
.level-badge.badge-b2 { background: rgba(249, 115, 22, 0.15); color: #fb923c; border: 1px solid rgba(249, 115, 22, 0.3); }
.level-badge.badge-c1 { background: rgba(168, 85, 247, 0.15); color: #c084fc; border: 1px solid rgba(168, 85, 247, 0.3); }

.topic-badge {
    font-size: 11px;
    font-weight: 600;
    color: var(--text-dim);
    background: var(--bg-main);
    border: 1px solid var(--border-color);
    padding: 2px 8px;
    border-radius: var(--radius-sm);
}

.listening-filters {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

.select-styled {
    background-color: var(--bg-main);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    color: var(--text-main);
    padding: 6px 10px;
    font-size: 13px;
    outline: none;
    cursor: pointer;
    transition: var(--transition);
}

.select-styled:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 2px var(--primary-dim);
}

.select-xs {
    font-size: 12px;
    padding: 4px 8px;
}

.listening-hero {
    background: linear-gradient(180deg, var(--bg-card) 0%, var(--bg-main) 100%);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 20px 24px;
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.listening-scenario-title {
    font-size: 18px;
    font-weight: 700;
    color: var(--text-main);
    margin: 0 0 4px 0;
}

.listening-subtitle {
    font-size: 13px;
    color: var(--text-muted);
    margin: 0;
}

.listening-audio-controls {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin-top: 4px;
}

@media (max-width: 600px) {
    .listening-audio-controls {
        grid-template-columns: 1fr;
    }
}

.audio-control-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 14px 16px;
    display: flex;
    flex-direction: column;
    gap: 8px;
    transition: var(--transition);
}

.audio-control-card:hover {
    border-color: var(--primary-dim);
}

.audio-control-label {
    font-size: 12px;
    font-weight: 600;
    color: var(--text-dim);
}

.listening-play-btn {
    width: 100%;
    justify-content: center;
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.listening-hint-bar {
    display: flex;
    align-items: center;
    gap: 12px;
}

.listening-hint-text {
    font-size: 13px;
    color: var(--text-muted);
    font-style: italic;
    background: var(--bg-main);
    border-left: 3px solid var(--primary);
    padding: 4px 10px;
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}

.listening-form {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.listening-revealed-card {
    background-color: var(--bg-main);
    border: 1px solid var(--border-color);
    border-left: 4px solid var(--primary);
    border-radius: var(--radius-md);
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 16px;
    animation: fadeIn 0.25s ease-out;
}

.revealed-section {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.revealed-label {
    font-size: 12px;
    font-weight: 700;
    color: var(--text-dim);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.revealed-val {
    font-size: 16px;
    color: #34d399;
}

.revealed-text {
    font-size: 15px;
    line-height: 1.5;
    color: var(--text-main);
    margin: 0;
}

.listening-next-bar {
    display: flex;
    justify-content: flex-end;
    margin-top: 8px;
    padding-top: 12px;
    border-top: 1px solid var(--border-color);
}


/* Summary Card */
.srs-summary-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 44px 32px;
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 20px;
    box-shadow: var(--shadow-lg);
    animation: fadeIn 0.3s ease-out;
}

.summary-trophy {
    font-size: 64px;
    animation: bounce 0.6s ease;
}

@keyframes bounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-16px); }
}

.srs-summary-card h2 {
    font-size: 28px;
    font-weight: 800;
}

.summary-lead {
    font-size: 15px;
    color: var(--text-muted);
    max-width: 480px;
}

.summary-metrics {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 16px;
    width: 100%;
    margin: 12px 0;
}

.metric-card {
    background-color: var(--bg-main);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 16px 12px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
}

.metric-val {
    font-size: 28px;
    font-weight: 800;
}

.metric-desc {
    font-size: 11px;
    color: var(--text-dim);
}

.text-success { color: var(--success); }
.text-primary { color: var(--primary); }

.summary-rates-bar {
    display: flex;
    gap: 12px;
    font-size: 13px;
    color: var(--text-muted);
    flex-wrap: wrap;
    justify-content: center;
}

.summary-buttons {
    display: flex;
    gap: 14px;
    margin-top: 12px;
    flex-wrap: wrap;
    justify-content: center;
}


/* Multiple Choice Quiz Mode */
.quiz-card {
    max-width: 680px;
    margin: 0 auto;
}

.quiz-hero {
    text-align: center;
    padding: 20px 0 16px 0;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 20px;
}

.quiz-prompt-row {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
}

.quiz-term-display {
    font-size: 32px;
    font-weight: 800;
    color: var(--text-main);
    letter-spacing: -0.02em;
}

.quiz-context-hint {
    margin-top: 8px;
    font-size: 14px;
    color: var(--text-muted);
    font-style: italic;
}

.quiz-options-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 14px;
    margin-bottom: 16px;
}

.quiz-option-btn {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 16px 18px;
    background: var(--bg-main);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-main);
    font-size: 15px;
    font-weight: 600;
    text-align: left;
    cursor: pointer;
    transition: all 0.15s ease;
    user-select: none;
}

.quiz-option-btn:hover:not(:disabled) {
    border-color: var(--primary);
    background: var(--bg-surface-hover);
    transform: translateY(-1px);
}

.quiz-option-btn:disabled {
    cursor: default;
}

.quiz-opt-num {
    width: 26px;
    height: 26px;
    border-radius: 50%;
    background: var(--bg-surface);
    border: 1px solid var(--border-color);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 12px;
    font-weight: 700;
    color: var(--text-muted);
    flex-shrink: 0;
}

.quiz-opt-text {
    flex: 1;
    line-height: 1.35;
}

.quiz-option-btn.opt-correct {
    background: rgba(34, 197, 94, 0.15) !important;
    border-color: var(--success) !important;
    color: var(--success) !important;
}

.quiz-option-btn.opt-correct .quiz-opt-num {
    background: var(--success);
    color: #ffffff;
    border-color: var(--success);
}

.quiz-option-btn.opt-wrong {
    background: rgba(239, 68, 68, 0.15) !important;
    border-color: var(--danger) !important;
    color: var(--danger) !important;
    animation: shake 0.3s ease;
}

.quiz-option-btn.opt-wrong .quiz-opt-num {
    background: var(--danger);
    color: #ffffff;
    border-color: var(--danger);
}

.quiz-next-bar {
    margin-top: 16px;
}

/* Active Typing Mode */
.typing-hero {
    text-align: center;
    padding: 16px 0 20px 0;
}

.typing-prompt-ru {
    font-size: 28px;
    font-weight: 800;
    color: var(--primary);
    margin: 8px 0;
}

.typing-context-hint {
    font-size: 14px;
    color: var(--text-muted);
    font-style: italic;
    background: var(--bg-main);
    padding: 8px 12px;
    border-radius: var(--radius-sm);
    display: inline-block;
    max-width: 90%;
    margin-top: 4px;
}


/* Analytics & Activity Heatmap Modal */
.stats-modal-window {
    max-width: 820px;
    width: 95%;
}

.stats-hero-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
    margin-bottom: 24px;
}

.stat-kpi-card {
    background: var(--bg-main);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 14px 12px;
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
}

.streak-kpi {
    border-color: rgba(249, 115, 22, 0.4);
    background: rgba(249, 115, 22, 0.05);
}

.kpi-icon {
    font-size: 24px;
}

.kpi-value {
    font-size: 26px;
    font-weight: 800;
    line-height: 1.1;
}

.kpi-label {
    font-size: 12px;
    font-weight: 600;
    color: var(--text-muted);
}

.kpi-sub {
    font-size: 11px;
    color: var(--text-dim);
}

.text-accent {
    color: #38bdf8;
}

/* GitHub Heatmap Section */
.heatmap-section {
    background: var(--bg-main);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 16px;
    margin-bottom: 20px;
}

.heatmap-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 14px;
    flex-wrap: wrap;
    gap: 8px;
}

.heatmap-header h4 {
    font-size: 15px;
    font-weight: 700;
}

.heatmap-legend {
    display: flex;
    align-items: center;
    gap: 5px;
    font-size: 11px;
    color: var(--text-dim);
}

.legend-cell {
    width: 12px;
    height: 12px;
    border-radius: 2px;
    display: inline-block;
}

.heatmap-container-wrap {
    overflow-x: auto;
    padding-bottom: 6px;
}

.heatmap-grid {
    display: grid;
    grid-auto-flow: column;
    grid-template-rows: repeat(7, 12px);
    gap: 4px;
    min-width: 600px;
}

.heatmap-cell {
    width: 12px;
    height: 12px;
    border-radius: 2px;
    background: rgba(255, 255, 255, 0.05);
    cursor: pointer;
    transition: transform 0.1s ease;
    position: relative;
}

.heatmap-cell:hover {
    transform: scale(1.3);
    z-index: 10;
    outline: 1px solid var(--text-main);
}

/* Heatmap Levels (GitHub-style intensity) */
.lvl-0 { background: rgba(255, 255, 255, 0.06); }
.lvl-1 { background: #166534; }  /* 1 review: soft green */
.lvl-2 { background: #22c55e; }  /* 2-3 reviews: vibrant green */
.lvl-3 { background: #4ade80; }  /* 4+ reviews: bright intense green */

[data-theme="light"] .lvl-0 { background: #e2e8f0; }
[data-theme="light"] .lvl-1 { background: #86efac; }
[data-theme="light"] .lvl-2 { background: #22c55e; }
[data-theme="light"] .lvl-3 { background: #15803d; }

.heatmap-footer-note {
    margin-top: 10px;
    color: var(--text-dim);
    font-size: 11px;
}

/* Segmented Mastery Progress Bar */
.mastery-section {
    background: var(--bg-main);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 16px;
}

.mastery-section h4 {
    font-size: 15px;
    font-weight: 700;
    margin-bottom: 12px;
}

.segmented-progress-bar {
    display: flex;
    height: 14px;
    background: var(--bg-surface);
    border-radius: var(--radius-full);
    overflow: hidden;
    margin-bottom: 12px;
    border: 1px solid var(--border-color);
}

.prog-segment {
    height: 100%;
    transition: width 0.3s ease;
}

.seg-mastered { background: #22c55e; }
.seg-review   { background: #38bdf8; }
.seg-learning { background: #f59e0b; }
.seg-new      { background: #64748b; }

.mastery-legend-row {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
    font-size: 12px;
}

.m-legend-item {
    display: flex;
    align-items: center;
    gap: 6px;
    color: var(--text-muted);
}

.dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    display: inline-block;
}

.dot-mastered { background: #22c55e; }
.dot-review   { background: #38bdf8; }
.dot-learning { background: #f59e0b; }
.dot-new      { background: #64748b; }
.dot-leech    { background: #ef4444; }

.text-danger  { color: #ef4444; }

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-4px); }
    75% { transform: translateX(4px); }
}


/* --- Responsive Mobile Overrides (max-width: 768px) --- */
@media (max-width: 768px) {
    /* 5. SRS Trainer */
    .srs-topbar {
        padding: 10px 12px;
        flex-direction: column;
        align-items: stretch;
        gap: 8px;
    }

    .srs-topbar-left, .srs-topbar-right {
        justify-content: space-between;
        width: 100%;
    }

    .srs-mode-switch {
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
        scrollbar-width: none;
    }

    .srs-mode-switch::-webkit-scrollbar {
        display: none;
    }

    .srs-tab {
        flex-shrink: 0;
        padding: 6px 10px;
        font-size: 12px;
    }

    .flashcard-wrapper {
        min-height: 270px;
        max-height: 48dvh;
    }

    .flashcard-inner {
        min-height: 270px;
    }

    .fc-main-term {
        font-size: 28px;
    }

    .fc-footer-hint {
        font-size: 11px;
    }

    .srs-rating-bar {
        grid-template-columns: 1fr 1fr;
        gap: 8px;
        width: 100%;
    }

    .btn-rate {
        min-height: 48px;
        padding: 8px 6px;
    }

    .rate-key {
        display: none;
    }

    .quiz-options-grid {
        grid-template-columns: 1fr;
        gap: 8px;
    }

    .quiz-option-btn {
        min-height: 48px;
        font-size: 14px;
        padding: 10px 14px;
    }


}