/* === CURRICULUM TOPIC STYLES === */

.curriculum-problems-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: var(--space-4);
    padding: var(--space-4) 0;
}

.curriculum-problem {
    background: var(--color-surface);
    border-radius: var(--radius-lg);
    padding: var(--space-4);
    border: 1px solid var(--color-border);
    transition: var(--transition);
    position: relative;
}

.curriculum-problem:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.curriculum-problem.correct {
    border-left: 4px solid var(--color-success);
    background: var(--color-success-light);
}

.curriculum-problem.incorrect {
    border-left: 4px solid var(--color-error);
    background: var(--color-error-light);
    animation: shake 0.3s ease;
}

.curriculum-problem .problem-number {
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: var(--space-2);
    font-size: 0.85em;
    background: rgba(99, 102, 241, 0.08);
    display: inline-block;
    padding: 2px var(--space-2);
    border-radius: var(--radius-full);
}

.curriculum-problem .problem-text {
    font-size: 1.05em;
    margin-bottom: var(--space-3);
    line-height: 1.5;
    font-family: var(--font-family);
    color: var(--color-text);
}

.curriculum-answer {
    width: 100px;
    padding: var(--space-2) var(--space-3);
    font-size: 1.2em;
    border: 1.5px solid var(--color-border);
    border-radius: 10px;
    text-align: center;
    font-family: var(--font-family);
    background: var(--color-surface);
    transition: var(--transition);
    color: var(--color-text);
}

.curriculum-answer:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

/* Skip Counting */
.skip-counting-row .sequence-row {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-2);
    align-items: center;
    justify-content: center;
}

.sc-cell {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 60px;
    height: 42px;
    font-size: 1.1em;
    font-weight: 700;
    font-family: var(--font-family);
}

.sc-given {
    background: var(--color-primary);
    color: white;
    border-radius: var(--radius-sm);
    padding: 0 var(--space-3);
}

.sc-answer {
    width: 70px;
    padding: var(--space-2);
    font-size: 1em;
    border: 2px dashed var(--color-primary-light);
    border-radius: var(--radius-sm);
    text-align: center;
    background: var(--color-surface);
    font-family: var(--font-family);
    color: var(--color-text);
}

.sc-answer:focus {
    border-style: solid;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
    outline: none;
}

.sc-answer.correct {
    background: var(--color-success-light);
    border-color: var(--color-success);
    border-style: solid;
}

.sc-answer.incorrect {
    background: var(--color-error-light);
    border-color: var(--color-error);
    border-style: solid;
}

/* Comparing Numbers */
.comparing-row {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-4);
    flex-wrap: wrap;
}

.compare-num {
    font-size: 1.6em;
    font-weight: 800;
    color: var(--color-text);
    font-family: var(--font-family);
}

.compare-buttons {
    display: flex;
    gap: var(--space-2);
}

.cmp-btn {
    width: 48px;
    height: 48px;
    font-size: 1.4em;
    font-weight: 700;
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-md);
    background: var(--color-surface);
    cursor: pointer;
    transition: var(--transition);
    color: var(--color-primary);
}

.cmp-btn:hover {
    background: rgba(99, 102, 241, 0.06);
    border-color: var(--color-primary-light);
}

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

/* Money */
.coin-display {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-2);
    justify-content: center;
    margin: var(--space-3) 0;
    font-size: 1.3em;
}

.coin {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #fde68a, #f59e0b);
    border-radius: 50%;
    width: 52px;
    height: 52px;
    font-size: 0.7em;
    font-weight: 700;
    border: 2px solid #d97706;
    box-shadow: var(--shadow-sm);
}

.coin-penny { background: linear-gradient(135deg, #fb923c, #ea580c); color: white; }
.coin-nickel { background: linear-gradient(135deg, #94a3b8, #64748b); color: white; }
.coin-dime { background: linear-gradient(135deg, #e2e8f0, #94a3b8); color: var(--color-text); }
.coin-quarter { background: linear-gradient(135deg, #e2e8f0, #94a3b8); color: var(--color-text); }

.money-answer-row, .measurement-answer-row {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    justify-content: center;
}

.cents-label, .unit-label {
    font-size: 1.1em;
    font-weight: 700;
    color: var(--color-primary);
    font-family: var(--font-family);
}

/* Time / Clock */
.clock-display {
    display: flex;
    justify-content: center;
    margin: var(--space-2) 0;
}

.clock-display svg {
    filter: drop-shadow(0 1px 3px rgba(0,0,0,0.08));
}

.time-answer-row {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-1);
}

.time-hour-input, .time-minute-input {
    width: 60px;
    padding: var(--space-2);
    font-size: 1.2em;
    border: 1.5px solid var(--color-border);
    border-radius: 10px;
    text-align: center;
    font-family: var(--font-family);
    background: var(--color-surface);
    color: var(--color-text);
}

.time-hour-input:focus, .time-minute-input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

.time-colon {
    font-size: 1.6em;
    font-weight: 700;
    color: var(--color-text);
}

/* Dark mode overrides for curriculum topics */
.dark-mode .curriculum-problem {
    background: var(--color-surface);
    border-color: var(--color-border);
}

.dark-mode .curriculum-problem .problem-text {
    color: var(--color-text);
}

.dark-mode .curriculum-problem .problem-number {
    color: var(--color-primary-light);
    background: rgba(129, 140, 248, 0.12);
}

.dark-mode .curriculum-answer,
.dark-mode .sc-answer,
.dark-mode .time-hour-input,
.dark-mode .time-minute-input {
    background: var(--color-surface);
    color: var(--color-text);
    border-color: var(--color-border);
}

.dark-mode .compare-num {
    color: var(--color-text);
}

.dark-mode .cmp-btn {
    background: var(--color-surface);
    color: var(--color-primary-light);
    border-color: var(--color-border);
}

.dark-mode .cmp-btn:hover {
    background: rgba(129, 140, 248, 0.1);
}

.dark-mode .sc-given {
    background: var(--color-primary-dark);
}

.dark-mode .clock-display svg circle {
    fill: var(--color-surface);
    stroke: var(--color-primary-light);
}

.dark-mode .clock-display svg text {
    fill: var(--color-text);
}

.dark-mode .clock-display svg line {
    stroke: var(--color-text);
}

.dark-mode .time-colon {
    color: var(--color-text);
}

.dark-mode .cents-label, .dark-mode .unit-label {
    color: var(--color-primary-light);
}

/* 3rd Grade: Multiplication arrays */
.big-equation {
    font-size: 1.5em;
    font-weight: 800;
    font-family: var(--font-family);
    color: var(--color-text);
}

.dark-mode .big-equation {
    color: var(--color-text);
}

.array-grid {
    display: inline-grid;
    gap: 3px;
    margin: var(--space-2) 0;
    justify-content: center;
}

.array-cell {
    width: 22px;
    height: 22px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-primary);
    color: white;
    border-radius: var(--space-1);
    font-size: 0.7em;
}

/* 3rd Grade: Fractions visual */
.fraction-visual {
    font-size: 1.5em;
    letter-spacing: 6px;
    margin: var(--space-2) 0;
    text-align: center;
}

/* 3rd Grade: Area grid */
.shape-grid {
    display: inline-block;
    margin: var(--space-2) 0;
    border: 1.5px solid var(--color-primary);
    border-radius: var(--space-1);
    padding: var(--space-1);
}

.grid-row {
    display: flex;
}

.grid-sq {
    width: 24px;
    height: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--color-border);
    background: rgba(99, 102, 241, 0.06);
    font-size: 0.7em;
}

.dark-mode .grid-sq {
    background: rgba(129, 140, 248, 0.1);
    border-color: var(--color-border);
}

.dark-mode .array-cell {
    background: var(--color-primary-dark);
}

/* Responsive for curriculum topics */
@media (max-width: 768px) {
    .curriculum-problems-grid {
        grid-template-columns: 1fr;
    }

    .comparing-row {
        gap: var(--space-2);
    }

    .compare-num {
        font-size: 1.3em;
    }

    .cmp-btn {
        width: 42px;
        height: 42px;
        font-size: 1.2em;
    }

    .coin {
        width: 44px;
        height: 44px;
        font-size: 0.6em;
    }
}

/* === CURRICULUM-SPECIFIC VISUAL MODELS === */

/* Number Bond (Eureka Math / Singapore Math) */
.number-bond-model {
    position: relative;
    width: 200px;
    height: 150px;
    margin: 10px auto;
}

.bond-whole {
    position: absolute;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 70px;
    height: 70px;
    border-radius: 50%;
    border: 3px solid var(--color-primary);
    background: var(--color-surface);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.3em;
    font-weight: 700;
    color: var(--color-text);
    z-index: 2;
}

.bond-part {
    position: absolute;
    bottom: 0;
    width: 60px;
    height: 60px;
    border-radius: 50%;
    border: 3px solid var(--color-primary-light);
    background: var(--color-surface);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2em;
    font-weight: 700;
    color: var(--color-text);
    z-index: 2;
}

.bond-part:first-of-type {
    left: 15px;
}

.bond-part:last-of-type {
    right: 15px;
}

.bond-line {
    position: absolute;
    width: 3px;
    height: 60px;
    background: var(--color-primary-light);
    z-index: 1;
}

.bond-line-left {
    top: 50px;
    left: 65px;
    transform: rotate(30deg);
}

.bond-line-right {
    top: 50px;
    right: 65px;
    transform: rotate(-30deg);
}

.bond-input {
    width: 50px !important;
    height: 36px;
    font-size: 1em;
    text-align: center;
    border: 2px dashed var(--color-primary);
    border-radius: var(--radius-sm);
    background: rgba(99, 102, 241, 0.05);
    color: var(--color-text);
    font-family: var(--font-family);
}

.bond-input:focus {
    border-style: solid;
    outline: none;
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

/* Bar Model (enVision) */
.bar-model {
    margin: 10px auto;
    max-width: 280px;
}

.bar-whole {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    color: white;
    border-radius: var(--radius-sm) var(--radius-sm) 0 0;
    padding: var(--space-2) var(--space-3);
    text-align: center;
    font-weight: 700;
    font-size: 1.1em;
    min-height: 42px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.bar-whole .bar-label {
    margin-right: var(--space-2);
}

.bar-parts-row {
    display: flex;
    border-radius: 0 0 var(--radius-sm) var(--radius-sm);
    overflow: hidden;
}

.bar-part {
    background: linear-gradient(135deg, var(--color-success-light) 0%, #a7f3d0 100%);
    padding: var(--space-2) var(--space-3);
    text-align: center;
    font-weight: 700;
    font-size: 1.1em;
    min-height: 42px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--color-border);
    color: var(--color-text);
}

.bar-part-alt {
    background: linear-gradient(135deg, var(--color-warning-light) 0%, #fde68a 100%);
}

.bar-input {
    width: 60px !important;
    height: 32px;
    font-size: 1em;
    text-align: center;
    border: 2px dashed white;
    border-radius: var(--radius-sm);
    background: rgba(255, 255, 255, 0.3);
    color: var(--color-text);
    font-family: var(--font-family);
}

.bar-whole .bar-input {
    border-color: rgba(255, 255, 255, 0.6);
    color: white;
    background: rgba(255, 255, 255, 0.2);
}

.bar-input:focus {
    border-style: solid;
    outline: none;
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

body.dark-mode .bar-part {
    background: linear-gradient(135deg, #064e3b 0%, #065f46 100%);
    color: #d1fae5;
}

body.dark-mode .bar-part-alt {
    background: linear-gradient(135deg, #78350f 0%, #92400e 100%);
    color: #fef3c7;
}

/* Fact Family (Saxon Math) */
.fact-family-model {
    text-align: center;
}

.ff-header {
    font-size: 0.85em;
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: var(--space-2);
    padding: var(--space-1) var(--space-3);
    background: rgba(99, 102, 241, 0.08);
    border-radius: var(--radius-full);
    display: inline-block;
}

/* Word Problem Strategy Badge */
.wp-strategy-badge {
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.08) 0%, rgba(99, 102, 241, 0.15) 100%);
    color: var(--color-primary-dark);
    padding: var(--space-2) var(--space-3);
    border-radius: var(--radius-sm);
    font-size: 0.85em;
    font-weight: 600;
    margin-bottom: var(--space-3);
    border-left: 3px solid var(--color-primary);
}

body.dark-mode .wp-strategy-badge {
    background: rgba(99, 102, 241, 0.15);
    color: var(--color-primary-light);
}

/* Curriculum info in sidebar */
.curriculum-info {
    margin-top: var(--space-1);
    font-size: 0.78em;
    font-weight: 600;
    color: var(--color-text-muted);
    min-height: 1.2em;
}

.curriculum-info strong {
    color: var(--color-primary);
}

/* Curriculum badge in header */
.curriculum-badge {
    display: none;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1) 0%, rgba(99, 102, 241, 0.2) 100%);
    color: var(--color-primary-dark);
    padding: 3px 12px;
    border-radius: var(--radius-full);
    font-size: 0.7em;
    font-weight: 700;
    margin-left: var(--space-2);
    vertical-align: middle;
}

body.dark-mode .curriculum-badge {
    color: var(--color-primary-light);
    background: rgba(99, 102, 241, 0.2);
}

/* === CURRICULUM STRATEGY BADGE (all grades) === */
.curriculum-strategy-badge {
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.08) 0%, rgba(99, 102, 241, 0.15) 100%);
    color: var(--color-primary-dark);
    padding: var(--space-1) var(--space-3);
    border-radius: var(--radius-sm);
    font-size: 0.8em;
    font-weight: 600;
    margin-bottom: var(--space-2);
    border-left: 3px solid var(--color-primary);
    display: inline-block;
}
body.dark-mode .curriculum-strategy-badge {
    background: rgba(99, 102, 241, 0.15);
    color: var(--color-primary-light);
}

/* === TAPE DIAGRAM (Grade 3 Multiplication/Division) === */
.tape-diagram {
    margin: var(--space-3) 0;
    text-align: center;
}
.tape-label {
    font-weight: 600;
    margin-bottom: var(--space-1);
    color: var(--color-text-muted);
    font-size: 0.9em;
}
.tape-segments {
    display: flex;
    gap: 2px;
    justify-content: center;
}
.tape-segment {
    background: linear-gradient(135deg, #818cf8 0%, #6366f1 100%);
    color: #fff;
    padding: 8px 14px;
    border-radius: 4px;
    font-weight: 700;
    font-size: 0.95em;
    min-width: 32px;
    text-align: center;
}

/* === BAR MODEL for Multiplication (Grade 3) === */
.bar-model-mult {
    margin: var(--space-3) 0;
    text-align: center;
}
.bar-model-mult .bar-total {
    background: rgba(99, 102, 241, 0.1);
    border: 2px dashed var(--color-primary);
    border-radius: var(--radius-sm);
    padding: 6px;
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: 4px;
}
.bar-model-mult .bar-segments {
    display: flex;
    gap: 2px;
    justify-content: center;
}
.bar-model-mult .bar-segment {
    background: linear-gradient(135deg, #34d399 0%, #10b981 100%);
    color: #fff;
    padding: 8px 14px;
    border-radius: 4px;
    font-weight: 700;
    min-width: 32px;
    text-align: center;
}
.bar-model-mult .bar-label {
    font-size: 0.85em;
    color: var(--color-text-muted);
    margin-top: 4px;
}

/* === FRACTION NUMBER LINE (Grade 3 Eureka) === */
.fraction-number-line {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    background: var(--color-surface);
    border-bottom: 3px solid var(--color-primary);
    padding: var(--space-2) var(--space-1);
    margin: var(--space-3) auto;
    max-width: 340px;
    position: relative;
}
.nl-mark {
    display: flex;
    flex-direction: column;
    align-items: center;
    font-size: 0.75em;
    color: var(--color-text-muted);
    position: relative;
}
.nl-mark::after {
    content: '';
    width: 2px;
    height: 12px;
    background: var(--color-text-muted);
    margin-top: 2px;
}
.nl-mark.nl-active {
    color: var(--color-primary);
    font-weight: 700;
}
.nl-mark.nl-active::after {
    background: var(--color-primary);
    height: 16px;
}

/* === FRACTION STRIPS (Grade 3/4 enVision) === */
.fraction-strips {
    margin: var(--space-3) auto;
    max-width: 300px;
}
.fstrip-whole {
    background: linear-gradient(135deg, #818cf8 0%, #6366f1 100%);
    color: #fff;
    text-align: center;
    padding: 8px;
    border-radius: var(--radius-sm);
    font-weight: 700;
    margin-bottom: 4px;
}
.fstrip-parts {
    display: flex;
    gap: 2px;
}
.fstrip-piece {
    flex: 1;
    text-align: center;
    padding: 8px 2px;
    border-radius: 3px;
    font-size: 0.8em;
    font-weight: 600;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    color: var(--color-text-muted);
}
.fstrip-piece.fstrip-shaded {
    background: linear-gradient(135deg, #34d399 0%, #10b981 100%);
    color: #fff;
    border-color: #10b981;
}

/* === ROUNDING NUMBER LINE (Grade 3) === */
.rounding-number-line {
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    padding: var(--space-3) var(--space-4);
    margin: var(--space-3) 0;
    position: relative;
    min-height: 40px;
}
.rnl-end {
    font-weight: 700;
    color: var(--color-primary);
    font-size: 1.1em;
}
.rnl-marker {
    position: absolute;
    bottom: -6px;
    color: var(--color-error);
    font-weight: 700;
    font-size: 0.85em;
    transform: translateX(-50%);
}

/* === AREA MODEL GRID (Grade 4 Long Multiplication) === */
.area-model-grid {
    margin: var(--space-3) auto;
    text-align: center;
}
.am-table {
    border-collapse: collapse;
    margin: 0 auto;
}
.am-table th, .am-table td {
    border: 2px solid var(--color-border);
    padding: 8px 16px;
    text-align: center;
    font-weight: 600;
}
.am-table th {
    background: rgba(99, 102, 241, 0.1);
    color: var(--color-primary);
}
.am-cell {
    background: var(--color-surface);
    color: var(--color-text);
    font-size: 0.95em;
}
.am-hint {
    font-size: 0.85em;
    color: var(--color-text-muted);
    margin-top: var(--space-1);
    font-style: italic;
}

/* === PARTIAL PRODUCTS HINT (Grade 4 enVision) === */
.partial-products-hint {
    background: rgba(52, 211, 153, 0.08);
    border-left: 3px solid #10b981;
    border-radius: var(--radius-sm);
    padding: var(--space-2) var(--space-3);
    margin: var(--space-2) 0;
}
.pp-step {
    font-family: monospace;
    font-size: 0.95em;
    margin: 2px 0;
    color: var(--color-text);
}
.pp-total {
    font-weight: 700;
    color: #10b981;
    font-size: 0.9em;
    margin-top: var(--space-1);
}

/* === PARTIAL QUOTIENTS HINT (Grade 4 Division) === */
.partial-quotients-hint, .pv-disk-hint {
    background: rgba(99, 102, 241, 0.06);
    border-left: 3px solid var(--color-primary);
    border-radius: var(--radius-sm);
    padding: var(--space-2) var(--space-3);
    margin: var(--space-2) 0;
    font-size: 0.9em;
}
.pq-step {
    font-family: monospace;
    margin: 2px 0;
}

/* === EQUIVALENT FRACTION STRIPS (Grade 4) === */
.ef-strip-visual {
    margin: var(--space-3) auto;
    max-width: 280px;
}
.ef-strip-whole, .ef-strip-equiv {
    display: flex;
    height: 32px;
    border-radius: var(--radius-sm);
    overflow: hidden;
    margin-bottom: 4px;
    border: 1px solid var(--color-border);
}
.ef-strip-piece {
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.8em;
    font-weight: 600;
    color: var(--color-text-muted);
}
.ef-strip-piece.ef-shaded {
    background: linear-gradient(135deg, #818cf8 0%, #6366f1 100%);
    color: #fff;
}

/* === DECIMAL GRID VISUAL (Grade 4) === */
.decimal-grid-visual {
    display: flex;
    gap: 3px;
    justify-content: center;
    margin: var(--space-3) 0;
}
.dg-cell {
    width: 28px;
    height: 28px;
    border: 2px solid var(--color-border);
    border-radius: 4px;
    display: inline-block;
}
.dg-cell.dg-shaded {
    background: linear-gradient(135deg, #818cf8 0%, #6366f1 100%);
    border-color: #6366f1;
}

/* === MNEMONIC BADGE (Grade 5 Order of Operations) === */
.mnemonic-badge {
    background: linear-gradient(135deg, rgba(251, 191, 36, 0.1) 0%, rgba(245, 158, 11, 0.15) 100%);
    color: #92400e;
    padding: var(--space-1) var(--space-3);
    border-radius: var(--radius-sm);
    font-size: 0.85em;
    margin-bottom: var(--space-2);
    border-left: 3px solid #f59e0b;
    display: inline-block;
}
body.dark-mode .mnemonic-badge {
    background: rgba(245, 158, 11, 0.12);
    color: #fbbf24;
}

/* === ESTIMATE HINT (Grade 5 Decimal Operations) === */
.estimate-hint {
    background: rgba(52, 211, 153, 0.08);
    padding: var(--space-1) var(--space-2);
    border-radius: var(--radius-sm);
    font-size: 0.85em;
    color: #065f46;
    margin-top: var(--space-1);
}
body.dark-mode .estimate-hint {
    color: #34d399;
    background: rgba(52, 211, 153, 0.1);
}

/* === FRACTION MULTIPLICATION AREA MODEL (Grade 5) === */
.fmul-area-model {
    margin: var(--space-3) auto;
    text-align: center;
}
.fmul-grid {
    display: inline-grid;
    gap: 2px;
    margin: 0 auto;
}
.fmul-cell {
    width: 28px;
    height: 28px;
    border: 1px solid var(--color-border);
    border-radius: 3px;
}
.fmul-overlap {
    background: linear-gradient(135deg, #818cf8 0%, #6366f1 100%);
}
.fmul-h {
    background: rgba(99, 102, 241, 0.2);
}
.fmul-v {
    background: rgba(52, 211, 153, 0.2);
}
.fmul-empty {
    background: var(--color-surface);
}
.fmul-labels {
    font-size: 0.85em;
    color: var(--color-text-muted);
    margin-top: var(--space-1);
}

/* === VOLUME LAYER HINT (Grade 5) === */
.volume-layer-hint {
    background: rgba(99, 102, 241, 0.06);
    padding: var(--space-1) var(--space-2);
    border-radius: var(--radius-sm);
    font-size: 0.85em;
    color: var(--color-text-muted);
    margin-top: var(--space-1);
}

/* Responsive adjustments for visual models */
@media (max-width: 480px) {
    .number-bond-model {
        width: 170px;
        height: 130px;
    }
    .bond-whole {
        width: 58px;
        height: 58px;
        font-size: 1.1em;
    }
    .bond-part {
        width: 50px;
        height: 50px;
        font-size: 1em;
    }
    .bar-model {
        max-width: 100%;
    }
}