/*
 * NFA Lesson Viewer — Phase 6B Styles
 * Inherits brand variables from subject-profile.css when loaded together.
 * Standalone fallback variables defined here for pages that load this alone.
 */

@import url('https://fonts.googleapis.com/css2?family=Playfair+Display:wght@400;600;700&family=Source+Serif+4:ital,opsz,wght@0,8..60,300;0,8..60,400;0,8..60,600;1,8..60,400&family=Space+Mono:wght@400;700&display=swap');

/* ── Root variables (fallback if subject-profile.css not loaded) ────────── */
.nfa-lesson-viewer {
    --nfa-navy:       #1e2855;
    --nfa-gold:       #E8C84A;
    --nfa-green:      #1A5C2E;
    --nfa-rust:       #8B3A1A;
    --nfa-cream:      #FAF8F2;
    --nfa-text:       #1a1a1a;
    --nfa-muted:      #666;
    --nfa-border:     #e0d8cc;
    --nfa-track-f:    #2E7D32;
    --nfa-track-a:    #1565C0;
    --nfa-track-fl:   #6A1B9A;
    --ff-display:     'Playfair Display', Georgia, serif;
    --ff-body:        'Source Serif 4', Georgia, serif;
    --ff-mono:        'Space Mono', monospace;
    font-family: var(--ff-body);
    color: var(--nfa-text);
    max-width: 860px;
    margin: 0 auto;
    padding: 0 20px 60px;
}

/* ── Lesson header ───────────────────────────────────────────────────────── */
.nfa-viewer-header {
    padding: 32px 0 20px;
    border-bottom: 3px solid var(--nfa-navy);
    margin-bottom: 0;
}
.nfa-viewer-breadcrumb { margin-bottom: 10px; }
.nfa-viewer-back {
    font-family: var(--ff-mono);
    font-size: 0.78rem;
    color: var(--nfa-navy);
    text-decoration: none;
    letter-spacing: .03em;
}
.nfa-viewer-back:hover { text-decoration: underline; }
.nfa-viewer-title-row {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    gap: 16px;
    flex-wrap: wrap;
}
.nfa-viewer-title {
    font-family: var(--ff-display);
    font-size: clamp(1.5rem, 4vw, 2.2rem);
    font-weight: 700;
    color: var(--nfa-navy);
    margin: 0;
    display: flex;
    align-items: center;
    gap: 14px;
}
.nfa-viewer-letter-badge {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: var(--nfa-navy);
    color: var(--nfa-gold);
    font-family: var(--ff-mono);
    font-weight: 700;
    font-size: 1.1rem;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}
.nfa-viewer-meta {
    display: flex;
    flex-direction: column;
    align-items: flex-end;
    gap: 4px;
    flex-shrink: 0;
}
.nfa-viewer-lesson-num,
.nfa-viewer-seat-time {
    font-family: var(--ff-mono);
    font-size: 0.78rem;
    color: var(--nfa-muted);
}

/* ── Stage selector ──────────────────────────────────────────────────────── */
.nfa-stage-selector {
    padding: 20px 0 16px;
    border-bottom: 1px solid var(--nfa-border);
    margin-bottom: 24px;
}
.nfa-stage-tabs {
    display: flex;
    gap: 4px;
    margin-bottom: 12px;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
}
.nfa-stage-tabs::-webkit-scrollbar { display: none; }
.nfa-stage-tab {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 10px 16px;
    border: 2px solid var(--nfa-border);
    border-radius: 3px;
    text-decoration: none;
    color: var(--nfa-muted);
    background: var(--nfa-cream);
    transition: border-color .2s, background .2s, color .2s;
    white-space: nowrap;
    flex-shrink: 0;
    min-width: 100px;
}
.nfa-stage-tab:hover { border-color: var(--nfa-navy); color: var(--nfa-navy); }
.nfa-stage-tab.active {
    border-color: var(--nfa-navy);
    background: var(--nfa-navy);
    color: var(--nfa-gold);
}
.nfa-stage-code {
    font-family: var(--ff-mono);
    font-weight: 700;
    font-size: 0.85rem;
}
.nfa-stage-label {
    font-size: 0.78rem;
    font-weight: 600;
    text-align: center;
    line-height: 1.2;
    margin: 3px 0 2px;
}
.nfa-stage-age {
    font-size: 0.7rem;
    opacity: 0.75;
}
.nfa-track-selector {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}
.nfa-track-btn {
    font-family: var(--ff-mono);
    font-size: 0.78rem;
    padding: 6px 16px;
    border-radius: 20px;
    text-decoration: none;
    border: 1.5px solid;
    transition: background .15s, color .15s;
}
.nfa-track-foundation { color: var(--nfa-track-f); border-color: var(--nfa-track-f); }
.nfa-track-achievement { color: var(--nfa-track-a); border-color: var(--nfa-track-a); }
.nfa-track-fluency     { color: var(--nfa-track-fl); border-color: var(--nfa-track-fl); }
.nfa-track-foundation.active  { background: var(--nfa-track-f);  color: #fff; }
.nfa-track-achievement.active { background: var(--nfa-track-a);  color: #fff; }
.nfa-track-fluency.active     { background: var(--nfa-track-fl); color: #fff; }

/* ── Progress bar ────────────────────────────────────────────────────────── */
.nfa-lesson-progress {
    margin-bottom: 24px;
    padding: 14px 18px;
    background: var(--nfa-cream);
    border: 1px solid var(--nfa-border);
    border-radius: 3px;
}
.nfa-progress-label {
    display: flex;
    justify-content: space-between;
    font-family: var(--ff-mono);
    font-size: 0.75rem;
    color: var(--nfa-muted);
    margin-bottom: 8px;
}
.nfa-progress-track {
    display: flex;
    gap: 4px;
}
.nfa-progress-seg {
    flex: 1;
    height: 8px;
    border-radius: 2px;
    background: #ddd;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background .3s;
    position: relative;
}
.nfa-progress-seg.done { background: var(--nfa-green); }
.nfa-progress-seg-label {
    position: absolute;
    bottom: -18px;
    font-family: var(--ff-mono);
    font-size: 0.62rem;
    color: var(--nfa-muted);
}

/* ── Section labels ──────────────────────────────────────────────────────── */
.nfa-section-label {
    display: flex;
    align-items: center;
    gap: 8px;
    font-family: var(--ff-mono);
    font-size: 0.72rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: .12em;
    color: var(--nfa-navy);
    margin-bottom: 16px;
    padding-bottom: 8px;
    border-bottom: 2px solid var(--nfa-gold);
}
.nfa-section-icon { font-size: 1rem; }

/* ── Lesson sections shared ─────────────────────────────────────────────── */
.nfa-teach-section,
.nfa-check-section,
.nfa-prove-section,
.nfa-essay-panel,
.nfa-vocab-panel {
    margin-bottom: 44px;
}

/* ── Vocabulary panel ────────────────────────────────────────────────────── */
.nfa-vocab-toggle {
    display: flex;
    align-items: center;
    gap: 10px;
    width: 100%;
    padding: 14px 18px;
    background: var(--nfa-cream);
    border: 1.5px solid var(--nfa-border);
    border-radius: 3px;
    cursor: pointer;
    font-family: var(--ff-mono);
    font-size: 0.85rem;
    font-weight: 700;
    color: var(--nfa-navy);
    text-align: left;
    transition: border-color .2s;
}
.nfa-vocab-toggle:hover { border-color: var(--nfa-navy); }
.nfa-vocab-toggle[aria-expanded="true"] { border-radius: 3px 3px 0 0; }
.nfa-vocab-count {
    margin-left: auto;
    background: var(--nfa-navy);
    color: var(--nfa-gold);
    font-size: 0.72rem;
    padding: 2px 8px;
    border-radius: 10px;
}
.nfa-vocab-chevron { transition: transform .25s; }
.nfa-vocab-toggle[aria-expanded="true"] .nfa-vocab-chevron { transform: rotate(180deg); }
.nfa-vocab-list {
    border: 1.5px solid var(--nfa-border);
    border-top: none;
    border-radius: 0 0 3px 3px;
    padding: 4px 0;
}
.nfa-vocab-dl { margin: 0; }
.nfa-vocab-entry {
    display: grid;
    grid-template-columns: 180px 1fr;
    gap: 12px;
    padding: 12px 18px;
    border-bottom: 1px solid var(--nfa-border);
    align-items: baseline;
}
.nfa-vocab-entry:last-child { border-bottom: none; }
.nfa-vocab-term {
    font-family: var(--ff-body);
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--nfa-navy);
}
.nfa-vocab-def {
    font-size: 0.9rem;
    color: var(--nfa-text);
    line-height: 1.5;
    margin: 0;
}
@media (max-width: 560px) {
    .nfa-vocab-entry { grid-template-columns: 1fr; gap: 4px; }
    .nfa-vocab-term { font-size: 0.85rem; }
}

/* ── Teach content ───────────────────────────────────────────────────────── */
.nfa-teach-body {
    font-size: 1.05rem;
    line-height: 1.85;
    color: #222;
}
.nfa-teach-body p { margin: 0 0 1.2em; }
.nfa-preview-content { /* no restrictions — teach always readable */ }

/* Preview inline note */
.nfa-preview-note {
    display: flex;
    gap: 12px;
    align-items: flex-start;
    padding: 14px 18px;
    background: #fffbeb;
    border: 1.5px solid var(--nfa-gold);
    border-radius: 3px;
    margin-top: 20px;
    font-size: 0.9rem;
}
.nfa-preview-note-icon { font-size: 1.2rem; flex-shrink: 0; margin-top: 2px; }
.nfa-preview-note-body { line-height: 1.55; color: #555; }
.nfa-preview-note-body a { color: var(--nfa-navy); font-weight: 600; }

/* ── Check questions ─────────────────────────────────────────────────────── */
.nfa-check-questions { display: flex; flex-direction: column; gap: 20px; }

.nfa-check-question {
    background: var(--nfa-cream);
    border: 1.5px solid var(--nfa-border);
    border-radius: 3px;
    padding: 20px;
    position: relative;
    transition: border-color .2s;
}
.nfa-check-question:focus-within { border-color: var(--nfa-navy); }

.nfa-q-stem { margin-bottom: 14px; }
.nfa-q-num {
    display: inline-flex;
    width: 26px; height: 26px;
    border-radius: 50%;
    background: var(--nfa-navy);
    color: var(--nfa-gold);
    font-family: var(--ff-mono);
    font-size: 0.72rem;
    font-weight: 700;
    align-items: center;
    justify-content: center;
    margin-right: 8px;
    flex-shrink: 0;
    vertical-align: middle;
}
.nfa-q-multi-hint {
    font-family: var(--ff-mono);
    font-size: 0.7rem;
    color: var(--nfa-track-a);
    background: #e3f2fd;
    padding: 2px 8px;
    border-radius: 10px;
    margin-right: 8px;
    vertical-align: middle;
}
.nfa-q-text { display: inline; font-size: 0.97rem; line-height: 1.6; margin: 0; }

/* Options */
.nfa-q-options { display: flex; flex-direction: column; gap: 8px; }
.nfa-q-option {
    display: flex;
    align-items: flex-start;
    gap: 10px;
    padding: 10px 14px;
    border: 1.5px solid var(--nfa-border);
    border-radius: 3px;
    cursor: pointer;
    transition: border-color .15s, background .15s;
    line-height: 1.4;
}
.nfa-q-option:hover { border-color: var(--nfa-navy); background: #f0f2f8; }
.nfa-q-option input { margin-top: 3px; flex-shrink: 0; accent-color: var(--nfa-navy); }
.nfa-option-key {
    font-family: var(--ff-mono);
    font-size: 0.72rem;
    font-weight: 700;
    color: var(--nfa-navy);
    min-width: 16px;
    flex-shrink: 0;
    margin-top: 1px;
}
.nfa-option-text { font-size: 0.93rem; }

/* TF options */
.nfa-tf-option { justify-content: flex-start; min-width: 100px; flex: 0 1 140px; }
.nfa-tf-label { font-weight: 600; font-size: 0.95rem; }
.nfa-q-options:has(.nfa-tf-option) { flex-direction: row; }

/* Text response */
.nfa-text-response-wrap { display: flex; flex-direction: column; gap: 8px; }
.nfa-text-response-input {
    width: 100%;
    padding: 10px 12px;
    border: 1.5px solid var(--nfa-border);
    border-radius: 3px;
    font-family: var(--ff-body);
    font-size: 0.93rem;
    line-height: 1.55;
    resize: vertical;
    min-height: 80px;
    transition: border-color .2s;
}
.nfa-text-response-input:focus { outline: none; border-color: var(--nfa-navy); }
.nfa-text-response-hint {
    font-family: var(--ff-mono);
    font-size: 0.72rem;
    color: var(--nfa-muted);
}

/* Artifact and image anchors */
.nfa-artifact-ref, .nfa-image-mc-context {
    padding: 10px 14px;
    background: #fff8e1;
    border: 1px solid #f0c040;
    border-radius: 3px;
    margin-bottom: 12px;
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 0.88rem;
    color: #5d4037;
}
.nfa-image-mc-loading { color: var(--nfa-muted); font-size: 0.85rem; }

/* Q category tag */
.nfa-q-category {
    margin-top: 10px;
    font-family: var(--ff-mono);
    font-size: 0.67rem;
    color: var(--nfa-muted);
    text-transform: uppercase;
    letter-spacing: .07em;
}

/* Result zones */
.nfa-q-result { margin-top: 12px; }
.nfa-result {
    display: flex;
    gap: 10px;
    align-items: flex-start;
    padding: 12px 16px;
    border-radius: 3px;
    font-size: 0.9rem;
}
.nfa-result--correct   { background: #e8f5e9; border: 1.5px solid #4caf50; }
.nfa-result--near-miss { background: #fff8e1; border: 1.5px solid #ff9800; }
.nfa-result--incorrect { background: #fce4ec; border: 1.5px solid #e57373; }
.nfa-result-icon { font-size: 1.2rem; flex-shrink: 0; }
.nfa-result-body p { margin: 6px 0 0; line-height: 1.5; color: #444; }

/* State — after submission */
.nfa-check-question.is-correct   { border-color: #4caf50; }
.nfa-check-question.is-near-miss { border-color: #ff9800; }
.nfa-check-question.is-wrong     { border-color: #e57373; }

/* Disable inputs after submit */
.nfa-check-question.submitted .nfa-q-option { pointer-events: none; opacity: 0.8; }
.nfa-check-question.submitted .nfa-text-response-input { pointer-events: none; }

/* Score bar */
.nfa-score-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 14px 20px;
    border-radius: 3px;
    margin-top: 16px;
    font-family: var(--ff-mono);
    font-size: 0.85rem;
}
.nfa-score-bar.passed   { background: #e8f5e9; border: 1.5px solid #4caf50; color: #2e7d32; }
.nfa-score-bar.retry    { background: #fce4ec; border: 1.5px solid #e57373; color: #c62828; }

/* Submit button */
.nfa-check-submit, .nfa-prove-submit {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    margin-top: 16px;
    padding: 13px 28px;
    background: var(--nfa-navy);
    color: var(--nfa-gold);
    font-family: var(--ff-mono);
    font-size: 0.82rem;
    font-weight: 700;
    letter-spacing: .04em;
    border: none;
    border-radius: 2px;
    cursor: pointer;
    transition: background .15s, transform .1s;
}
.nfa-check-submit:hover, .nfa-prove-submit:hover { background: #2a3870; transform: translateY(-1px); }
.nfa-check-submit:disabled, .nfa-prove-submit:disabled { opacity: 0.5; cursor: not-allowed; transform: none; }
.nfa-check-results { margin-top: 8px; }

/* ── Prove prompts ───────────────────────────────────────────────────────── */
.nfa-prove-prompts { display: flex; flex-direction: column; gap: 28px; }

/* Analytical pairs */
.nfa-analytical-pairs {
    display: flex;
    align-items: center;
    gap: 10px;
    flex-wrap: wrap;
    margin-bottom: 14px;
    padding: 10px 16px;
    background: #f0f4ff;
    border: 1px solid #c5cae9;
    border-radius: 3px;
    font-size: 0.85rem;
}
.nfa-pairs-label { font-family: var(--ff-mono); font-size: 0.72rem; color: var(--nfa-muted); text-transform: uppercase; }
.nfa-pair-tag {
    background: var(--nfa-navy);
    color: var(--nfa-gold);
    font-family: var(--ff-mono);
    font-size: 0.72rem;
    padding: 3px 10px;
    border-radius: 10px;
}

/* Compliance flags */
.nfa-prove-compliance-flags {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    margin-bottom: 14px;
}
.nfa-flag {
    font-family: var(--ff-mono);
    font-size: 0.72rem;
    padding: 4px 10px;
    border-radius: 2px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: .05em;
}
.nfa-flag-ceiling  { background: #fff3e0; color: #e65100; border: 1px solid #ffcc80; }
.nfa-flag-boundary { background: #e8f5e9; color: #1b5e20; border: 1px solid #a5d6a7; }
.nfa-flag-stop     { background: #fce4ec; color: #880e4f; border: 1px solid #f48fb1; }

/* Prove prompt card */
.nfa-prove-prompt {
    background: var(--nfa-cream);
    border: 1.5px solid var(--nfa-border);
    border-radius: 3px;
    padding: 22px;
}
.nfa-prove-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 14px;
}
.nfa-prove-num-badge {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: var(--nfa-navy);
    color: var(--nfa-gold);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    flex-shrink: 0;
    gap: 0;
}
.nfa-prove-icon { font-size: 1rem; line-height: 1; }
.nfa-prove-num  { font-family: var(--ff-mono); font-size: 0.65rem; font-weight: 700; line-height: 1; }
.nfa-prove-header-text { display: flex; flex-direction: column; gap: 3px; }
.nfa-prove-type-label { font-family: var(--ff-mono); font-size: 0.75rem; font-weight: 700; color: var(--nfa-navy); text-transform: uppercase; letter-spacing: .06em; }
.nfa-prove-seat-time  { font-family: var(--ff-mono); font-size: 0.72rem; color: var(--nfa-muted); }

/* Goal statement */
.nfa-prove-goal {
    background: var(--nfa-navy);
    padding: 12px 18px;
    border-radius: 2px;
    margin-bottom: 14px;
}
.nfa-prove-goal-text {
    font-family: var(--ff-display);
    font-style: italic;
    font-size: 0.97rem;
    color: #fff;
}

/* Artifact indicator */
.nfa-prove-artifact {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 14px;
    background: #fff8e1;
    border: 1px solid #f0c040;
    border-radius: 3px;
    margin-bottom: 12px;
    font-size: 0.87rem;
    color: #5d4037;
}

/* Task breakdown DL */
.nfa-prove-task-dl { margin: 0 0 16px; display: flex; flex-direction: column; gap: 6px; }
.nfa-prove-task-row { display: grid; grid-template-columns: 160px 1fr; gap: 12px; }
.nfa-prove-task-label {
    font-family: var(--ff-mono);
    font-size: 0.72rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: .07em;
    color: var(--nfa-muted);
    padding-top: 2px;
}
.nfa-prove-task-text { font-size: 0.93rem; line-height: 1.55; color: var(--nfa-text); margin: 0; }
.nfa-prove-task-raw { font-size: 0.93rem; line-height: 1.6; margin: 0 0 16px; }
@media (max-width: 560px) { .nfa-prove-task-row { grid-template-columns: 1fr; gap: 2px; } }

/* Textarea */
.nfa-prove-input-wrap { margin-top: 12px; }
.nfa-prove-textarea {
    width: 100%;
    box-sizing: border-box;
    padding: 12px 14px;
    border: 1.5px solid var(--nfa-border);
    border-radius: 3px;
    font-family: var(--ff-body);
    font-size: 0.97rem;
    line-height: 1.65;
    resize: vertical;
    transition: border-color .2s;
    background: #fff;
}
.nfa-prove-textarea:focus { outline: none; border-color: var(--nfa-navy); }
.nfa-prove-input-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 6px;
    flex-wrap: wrap;
    gap: 6px;
}
.nfa-word-count {
    font-family: var(--ff-mono);
    font-size: 0.72rem;
    color: var(--nfa-muted);
    transition: color .2s;
}
.nfa-word-count.under-min { color: #e57373; }
.nfa-word-count.at-min    { color: var(--nfa-green); }
.nfa-word-min { opacity: 0.7; }
.nfa-prove-pswa-tag {
    font-family: var(--ff-mono);
    font-size: 0.67rem;
    background: #f0f4ff;
    color: #3949ab;
    padding: 2px 8px;
    border-radius: 10px;
    border: 1px solid #c5cae9;
}
.nfa-prove-response-status { margin-top: 10px; }

/* ── Essay panel ─────────────────────────────────────────────────────────── */
.nfa-essay-meta {
    display: flex;
    gap: 14px;
    margin-bottom: 14px;
}
.nfa-essay-wc, .nfa-essay-version {
    font-family: var(--ff-mono);
    font-size: 0.75rem;
    color: var(--nfa-muted);
    background: var(--nfa-cream);
    padding: 3px 10px;
    border: 1px solid var(--nfa-border);
    border-radius: 10px;
}
.nfa-essay-content {
    font-size: 1rem;
    line-height: 1.85;
    color: #222;
    padding: 0 0 0 20px;
    border-left: 3px solid var(--nfa-gold);
    max-height: 600px;
    overflow-y: auto;
}
.nfa-essay-content p { margin: 0 0 1.2em; }

/* ── Locked overlay ──────────────────────────────────────────────────────── */
.nfa-locked-overlay {
    background: var(--nfa-cream);
    border: 2px dashed var(--nfa-border);
    border-radius: 4px;
    padding: 48px 32px;
    text-align: center;
}
.nfa-locked-inner { max-width: 440px; margin: 0 auto; }
.nfa-locked-icon  { font-size: 2.8rem; margin-bottom: 14px; }
.nfa-locked-heading {
    font-family: var(--ff-display);
    font-size: 1.4rem;
    color: var(--nfa-navy);
    margin: 0 0 10px;
}
.nfa-locked-body { color: var(--nfa-muted); font-size: 0.95rem; line-height: 1.6; margin: 0 0 20px; }
.nfa-locked-cta {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 14px;
    flex-wrap: wrap;
    margin-bottom: 14px;
}
.nfa-locked-badge {
    font-family: var(--ff-mono);
    font-size: 0.75rem;
    color: var(--nfa-muted);
    background: #f5f5f5;
    padding: 4px 12px;
    border-radius: 10px;
    border: 1px solid var(--nfa-border);
}
.nfa-locked-btn {
    background: var(--nfa-navy);
    color: var(--nfa-gold);
    font-family: var(--ff-mono);
    font-size: 0.78rem;
    font-weight: 700;
    padding: 11px 22px;
    border-radius: 2px;
    text-decoration: none;
    transition: background .15s;
}
.nfa-locked-btn:hover { background: #2a3870; }
.nfa-locked-logged-in, .nfa-locked-logged-out {
    font-size: 0.83rem;
    color: var(--nfa-muted);
    margin: 0;
}
.nfa-locked-logged-in a, .nfa-locked-logged-out a { color: var(--nfa-navy); }

/* ── Viewer error ────────────────────────────────────────────────────────── */
.nfa-viewer-error {
    padding: 24px;
    background: #fff3f3;
    border: 1.5px solid #e57373;
    border-radius: 3px;
    color: #c62828;
}

/* ── Utility ─────────────────────────────────────────────────────────────── */
.nfa-sr-only {
    position: absolute; width: 1px; height: 1px;
    padding: 0; margin: -1px; overflow: hidden;
    clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}

/* ── Responsive ─────────────────────────────────────────────────────────── */
@media (max-width: 640px) {
    .nfa-lesson-viewer { padding: 0 14px 40px; }
    .nfa-stage-tab { min-width: 80px; padding: 8px 10px; }
    .nfa-stage-label { display: none; }
    .nfa-vocab-entry { grid-template-columns: 1fr; }
    .nfa-prove-task-row { grid-template-columns: 1fr; }
    .nfa-locked-overlay { padding: 32px 20px; }
}