:root {
    --sf-ink: #172033;
    --sf-muted: #5d6677;
    --sf-blue: #174f87;
    --sf-blue-dark: #0b3158;
    --sf-coral: #b63f39;
    --sf-cream: #f7f2e8;
    --sf-paper: #fffdf8;
    --sf-mint: #dff1e7;
    --sf-line: #d8dee8;
    --sf-success: #176b45;
    --sf-error: #a62d2d;
    --sf-shadow: 0 18px 50px rgba(23, 32, 51, 0.1);
}

.solfeggio-page {
    background: var(--sf-paper);
    color: var(--sf-ink);
}

.sf-shell {
    min-height: 70vh;
    overflow: hidden;
}

.sf-wrap {
    width: min(1180px, calc(100% - 2rem));
    margin: 0 auto;
}

.sf-reading-wrap {
    width: min(820px, calc(100% - 2rem));
}

.sf-hero,
.sf-module-hero,
.sf-lesson-hero {
    position: relative;
    overflow: hidden;
    color: #fff;
    background:
        radial-gradient(circle at 82% 18%, rgba(231, 93, 85, 0.38), transparent 25rem),
        linear-gradient(135deg, var(--sf-blue-dark), var(--sf-blue));
}

.sf-hero::after,
.sf-module-hero::after,
.sf-lesson-hero::after {
    content: "♪";
    position: absolute;
    right: max(2rem, calc((100vw - 1180px) / 2));
    bottom: -5rem;
    color: rgba(255, 255, 255, 0.08);
    font: 20rem/1 Georgia, serif;
    transform: rotate(-8deg);
    pointer-events: none;
}

.sf-hero {
    padding: clamp(5rem, 10vw, 9rem) 0 clamp(4rem, 8vw, 7rem);
}

.sf-module-hero,
.sf-lesson-hero {
    padding: 3.5rem 0 4.5rem;
}

.sf-hero h1,
.sf-module-hero h1,
.sf-lesson-hero h1 {
    max-width: 880px;
    margin: 0 0 1.25rem;
    color: #fff;
    font-size: clamp(2.6rem, 7vw, 5.8rem);
    line-height: 0.98;
    letter-spacing: -0.045em;
}

.sf-module-hero h1,
.sf-lesson-hero h1 {
    font-size: clamp(2.2rem, 5vw, 4.5rem);
}

.sf-eyebrow,
.sf-kicker,
.sf-module-level {
    margin: 0 0 0.8rem;
    color: var(--sf-coral);
    font-size: 0.78rem;
    font-weight: 800;
    letter-spacing: 0.13em;
    text-transform: uppercase;
}

.sf-hero .sf-eyebrow,
.sf-module-hero .sf-eyebrow,
.sf-lesson-hero .sf-eyebrow {
    color: #ffd6cf;
}

.sf-hero__lead {
    max-width: 760px;
    margin: 0;
    font-size: clamp(1.08rem, 2.2vw, 1.42rem);
    line-height: 1.65;
}

.sf-hero__facts {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    margin-top: 2rem;
}

.sf-hero__facts span {
    border: 1px solid rgba(255, 255, 255, 0.34);
    border-radius: 999px;
    padding: 0.55rem 0.9rem;
    background: rgba(255, 255, 255, 0.08);
    font-weight: 700;
}

.sf-local-note {
    max-width: 650px;
    margin: 1.3rem 0 0;
    color: rgba(255, 255, 255, 0.77);
    font-size: 0.9rem;
}

.sf-section {
    padding-top: clamp(3.5rem, 8vw, 6.5rem);
    padding-bottom: clamp(3.5rem, 8vw, 6.5rem);
}

.sf-section--soft {
    background: var(--sf-cream);
}

.sf-section-heading {
    max-width: 760px;
    margin-bottom: 2.4rem;
}

.sf-section-heading h2,
.sf-lesson-section h2 {
    margin: 0 0 0.9rem;
    color: var(--sf-ink);
    font-size: clamp(1.75rem, 4vw, 3rem);
    line-height: 1.1;
    letter-spacing: -0.03em;
}

.sf-section-heading > p:last-child {
    color: var(--sf-muted);
    font-size: 1.08rem;
    line-height: 1.65;
}

.sf-module-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 1.25rem;
}

.sf-module-card {
    display: flex;
    min-height: 320px;
    flex-direction: column;
    border: 1px solid var(--sf-line);
    border-radius: 1.25rem;
    padding: clamp(1.35rem, 3vw, 2rem);
    background: #fff;
    box-shadow: 0 6px 24px rgba(23, 32, 51, 0.04);
    transition: transform 180ms ease, box-shadow 180ms ease;
}

.sf-module-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--sf-shadow);
}

.sf-module-card__top,
.sf-module-card__footer,
.sf-exercise-heading {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
}

.sf-module-number {
    color: var(--sf-blue);
    font: 700 2.25rem/1 Georgia, serif;
}

.sf-status {
    border-radius: 999px;
    padding: 0.35rem 0.65rem;
    background: #eef1f5;
    color: var(--sf-muted);
    font-size: 0.75rem;
    font-weight: 800;
}

.sf-status.is-open {
    background: var(--sf-mint);
    color: var(--sf-success);
}

.sf-module-level {
    margin-top: 2rem;
}

.sf-module-card h3 {
    margin: 0 0 0.8rem;
    font-size: clamp(1.35rem, 2.4vw, 1.85rem);
    line-height: 1.16;
}

.sf-module-card h3 a {
    color: var(--sf-ink);
    text-decoration: none;
}

.sf-module-card > p:not(.sf-module-level) {
    color: var(--sf-muted);
    line-height: 1.6;
}

.sf-module-card__footer {
    margin-top: auto;
    border-top: 1px solid var(--sf-line);
    padding-top: 1rem;
    color: var(--sf-muted);
    font-size: 0.88rem;
}

.sf-arrow-link {
    color: var(--sf-blue);
    font-weight: 800;
    text-decoration: none;
}

.sf-start-card {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 2rem;
    border-radius: 1.5rem;
    padding: clamp(1.5rem, 4vw, 3rem);
    background: #fff;
    box-shadow: var(--sf-shadow);
}

.sf-start-card h2 {
    margin: 0.2rem 0 0.6rem;
    color: var(--sf-ink);
}

.sf-button,
.sf-audio-button,
.sf-check-button {
    display: inline-flex;
    min-height: 48px;
    align-items: center;
    justify-content: center;
    border: 0;
    border-radius: 0.75rem;
    padding: 0.8rem 1.2rem;
    background: var(--sf-coral);
    color: #fff;
    font: inherit;
    font-weight: 800;
    text-align: center;
    text-decoration: none;
    cursor: pointer;
}

.sf-button:hover,
.sf-audio-button:hover,
.sf-check-button:hover {
    background: #96302b;
    color: #fff;
}

.sf-button:focus-visible,
.sf-audio-button:focus-visible,
.sf-check-button:focus-visible,
.sf-flashcard:focus-visible,
.sf-question input:focus-visible + span {
    outline: 3px solid #ffbf47;
    outline-offset: 3px;
}

.sf-breadcrumbs {
    display: flex;
    flex-wrap: wrap;
    gap: 0.55rem;
    margin-bottom: 2rem;
    color: rgba(255, 255, 255, 0.72);
    font-size: 0.88rem;
}

.sf-breadcrumbs a {
    color: #fff;
}

.sf-lesson-list {
    display: grid;
    gap: 0.85rem;
}

.sf-lesson-card {
    display: grid;
    grid-template-columns: 90px minmax(0, 1fr) auto auto;
    gap: 1rem;
    align-items: center;
    border: 1px solid var(--sf-line);
    border-radius: 1rem;
    padding: 1.2rem;
    background: #fff;
    color: var(--sf-ink);
    text-decoration: none;
}

.sf-lesson-card:hover {
    border-color: var(--sf-blue);
    color: var(--sf-ink);
    box-shadow: 0 8px 25px rgba(23, 79, 135, 0.1);
}

.sf-lesson-card__number,
.sf-lesson-card > span:nth-of-type(2),
.sf-lesson-state {
    color: var(--sf-muted);
    font-size: 0.84rem;
}

.sf-lesson-state.is-complete {
    color: var(--sf-success);
    font-weight: 800;
}

.sf-empty-state {
    border: 1px dashed #b6bfcc;
    border-radius: 1rem;
    padding: 1.4rem;
    background: #fafbfc;
}

.sf-topic-list {
    display: grid;
    max-width: 900px;
    gap: 0.8rem;
    margin: 0;
    padding: 0;
    list-style: none;
    counter-reset: sf-topic;
}

.sf-topic {
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto;
    gap: 1rem;
    align-items: start;
    border-bottom: 1px solid rgba(23, 32, 51, 0.14);
    padding: 1.05rem 0 1.05rem 3.25rem;
    counter-increment: sf-topic;
    position: relative;
}

.sf-topic::before {
    content: counter(sf-topic, decimal-leading-zero);
    position: absolute;
    top: 1rem;
    left: 0;
    color: var(--sf-blue);
    font-weight: 800;
}

.sf-topic p {
    margin: 0.35rem 0 0;
    color: var(--sf-muted);
}

.sf-topic > span {
    border-radius: 999px;
    padding: 0.3rem 0.6rem;
    background: #e8e2d8;
    color: var(--sf-muted);
    font-size: 0.75rem;
    font-weight: 800;
}

.sf-topic.is-available > span {
    background: var(--sf-mint);
    color: var(--sf-success);
}

.sf-progress-box {
    display: inline-flex;
    gap: 0.65rem;
    margin-top: 1.6rem;
    border: 1px solid rgba(255, 255, 255, 0.28);
    border-radius: 0.8rem;
    padding: 0.7rem 0.9rem;
    background: rgba(255, 255, 255, 0.08);
}

.sf-progress-box span {
    color: rgba(255, 255, 255, 0.72);
}

.sf-lesson-layout {
    padding-top: 3.5rem;
    padding-bottom: 5rem;
}

.sf-lesson-section {
    margin-bottom: 4rem;
    scroll-margin-top: 2rem;
}

.sf-lesson-toc {
    margin-bottom: 2rem;
    border: 1px solid var(--sf-line);
    border-radius: 1rem;
    padding: 1.25rem;
    background: #fff;
}

.sf-lesson-toc h2 {
    margin-bottom: 0.85rem;
    font-size: 1.35rem;
}

.sf-toc-links {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.45rem 1rem;
}

.sf-toc-links a {
    color: var(--sf-blue);
    line-height: 1.4;
    text-decoration-thickness: 1px;
    text-underline-offset: 0.18em;
}

.sf-toc-links small {
    color: var(--sf-muted);
}

.sf-before-lesson {
    border: 2px solid var(--sf-blue);
    border-radius: 1.2rem;
    padding: clamp(1.25rem, 4vw, 2rem);
    background: #f6f9fd;
}

.sf-entry-checks {
    display: grid;
    gap: 0.9rem;
    margin: 1.25rem 0 1.75rem;
}

.sf-entry-check {
    display: grid;
    gap: 0.55rem;
    border: 1px solid var(--sf-line);
    border-radius: 1rem;
    padding: 1rem;
    background: #fff;
}

.sf-entry-check legend {
    display: flex;
    gap: 0.65rem;
    margin-bottom: 0.4rem;
    font-weight: 800;
    line-height: 1.45;
}

.sf-entry-check legend span {
    display: inline-grid;
    width: 1.8rem;
    height: 1.8rem;
    flex: 0 0 1.8rem;
    place-items: center;
    border-radius: 50%;
    background: var(--sf-blue);
    color: #fff;
    font-size: 0.75rem;
}

.sf-entry-check label {
    display: flex;
    gap: 0.55rem;
    align-items: flex-start;
    border-radius: 0.65rem;
    padding: 0.55rem 0.7rem;
    background: #f7f9fc;
    cursor: pointer;
}

.sf-entry-check .sf-check-button {
    width: max-content;
    margin-top: 0.35rem;
}

.sf-entry-check.is-correct {
    border-color: #78b99a;
}

.sf-entry-check.is-incorrect {
    border-color: #d88d8d;
}

.sf-review-link {
    display: inline-block;
    color: inherit;
    font-weight: 900;
    text-decoration: underline;
    text-underline-offset: 0.16em;
}

.sf-link-group {
    margin-top: 1.4rem;
}

.sf-link-group h3,
.sf-link-group summary {
    margin-bottom: 0.75rem;
    color: var(--sf-blue-dark);
    font-weight: 900;
}

.sf-link-group summary,
.sf-symbol-legend summary,
.sf-advanced-disclosure summary,
.sf-station-advanced summary,
.sf-mode-group--advanced summary {
    cursor: pointer;
}

.sf-learning-links {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.75rem;
}

.sf-learning-links > a {
    display: grid;
    gap: 0.3rem;
    border: 1px solid var(--sf-line);
    border-radius: 0.85rem;
    padding: 0.85rem;
    background: #fff;
    color: var(--sf-blue-dark);
    text-decoration: none;
}

.sf-learning-links > a:hover,
.sf-learning-links > a:focus-visible {
    border-color: var(--sf-blue);
    box-shadow: 0 5px 18px rgba(29, 68, 110, 0.1);
}

.sf-learning-links span {
    color: var(--sf-muted);
    font-size: 0.88rem;
    line-height: 1.45;
}

.sf-learning-links .is-advanced {
    border-color: #c8b1dd;
    background: #fbf7ff;
}

.sf-symbol-legend {
    margin-top: 1.5rem;
    border-top: 1px solid var(--sf-line);
    padding-top: 1rem;
}

.sf-symbol-legend dl {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.6rem;
}

.sf-symbol-legend dl > div {
    display: grid;
    grid-template-columns: minmax(52px, auto) 1fr;
    gap: 0.6rem;
    border-radius: 0.65rem;
    padding: 0.65rem;
    background: #fff;
}

.sf-symbol-legend dt {
    color: var(--sf-blue-dark);
    font-weight: 900;
}

.sf-symbol-legend dd {
    margin: 0;
    color: var(--sf-muted);
}

.sf-theory-section--advanced {
    border: 1px solid #d8c7e7;
    border-radius: 1rem;
    padding: 1.25rem;
    background: #fcf9ff;
}

.sf-advanced-disclosure summary {
    display: grid;
    gap: 0.25rem;
    list-style-position: outside;
}

.sf-advanced-disclosure summary strong {
    color: var(--sf-blue-dark);
    font: 700 clamp(1.45rem, 3vw, 2.15rem)/1.2 Georgia, serif;
}

.sf-advanced-disclosure[open] .sf-richtext {
    margin-top: 1.25rem;
}

.sf-objectives {
    border-left: 5px solid var(--sf-coral);
    border-radius: 0 1rem 1rem 0;
    padding: 1.6rem 1.8rem;
    background: var(--sf-cream);
}

.sf-objectives ul {
    margin: 1rem 0 0;
}

.sf-objectives li {
    margin: 0.55rem 0;
}

.sf-richtext,
.sf-theory-section > p,
.sf-lesson-section > p {
    font-size: 1.04rem;
    line-height: 1.76;
}

.sf-richtext p {
    margin: 0 0 1rem;
}

.sf-point-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.9rem;
}

.sf-point-card,
.sf-mistakes article {
    border: 1px solid var(--sf-line);
    border-radius: 1rem;
    padding: 1.2rem;
    background: #fff;
}

.sf-point-card h3,
.sf-mistakes h3 {
    margin: 0 0 0.5rem;
    color: var(--sf-blue-dark);
    font-size: 1.05rem;
}

.sf-point-card p,
.sf-mistakes p {
    margin: 0;
    color: var(--sf-muted);
    line-height: 1.6;
}

.sf-mistakes {
    display: grid;
    gap: 0.8rem;
}

.sf-flashcards {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 1rem;
}

.sf-flashcard {
    min-height: 180px;
    border: 2px solid var(--sf-blue);
    border-radius: 1rem;
    padding: 1.25rem;
    background: #fff;
    color: var(--sf-ink);
    font: inherit;
    font-size: 1.1rem;
    font-weight: 800;
    cursor: pointer;
}

.sf-flashcard[aria-expanded="true"] {
    background: var(--sf-blue-dark);
    color: #fff;
}

.sf-interactive-section {
    border-radius: 1.35rem;
    margin-right: clamp(-1rem, -3vw, -2.5rem);
    margin-left: clamp(-1rem, -3vw, -2.5rem);
    padding: clamp(1.25rem, 4vw, 2.5rem);
    background: #f2f6fb;
}

.sf-guided-practice {
    border: 1px solid #b9cce1;
    border-radius: 1.35rem;
    margin-right: clamp(-1rem, -3vw, -2.5rem);
    margin-left: clamp(-1rem, -3vw, -2.5rem);
    padding: clamp(1.25rem, 4vw, 2.5rem);
    background: linear-gradient(145deg, #edf5fd, #f8fbff);
}

.sf-guided-practice__header {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    align-items: flex-start;
}

.sf-guided-practice__header h2 {
    margin-bottom: 0;
}

.sf-guided-practice__state {
    flex: 0 0 auto;
    border-radius: 999px;
    padding: 0.55rem 0.75rem;
    background: #fff;
    color: var(--sf-muted);
    font-size: 0.78rem;
    font-weight: 900;
}

.sf-guided-practice.is-complete .sf-guided-practice__state {
    background: var(--sf-mint);
    color: var(--sf-success);
}

.sf-guided-practice__observe {
    display: grid;
    grid-template-columns: minmax(220px, 0.8fr) minmax(0, 1.2fr);
    gap: 1.5rem;
    align-items: center;
    margin: 1.5rem 0;
    border-radius: 1rem;
    padding: 1.25rem;
    background: #fff;
}

.sf-guided-practice__observe h3 {
    margin: 0 0 0.6rem;
    color: var(--sf-blue-dark);
}

.sf-guided-practice__observe p:last-child {
    margin-bottom: 0;
    color: var(--sf-muted);
    line-height: 1.65;
}

.sf-concept-visual {
    position: relative;
    display: flex;
    min-height: 150px;
    align-items: center;
    justify-content: center;
    gap: 0.45rem;
    overflow: hidden;
    border-radius: 0.9rem;
    padding: 1rem;
    background: var(--sf-blue-dark);
}

.sf-concept-visual span {
    display: block;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: #fff;
}

.sf-concept-visual--sound span,
.sf-concept-visual--ear span {
    height: calc(18px + var(--visual-step, 0px));
    border-radius: 999px;
}

.sf-concept-visual--sound span:nth-child(2),
.sf-concept-visual--sound span:nth-child(6),
.sf-concept-visual--ear span:nth-child(2),
.sf-concept-visual--ear span:nth-child(6) { height: 54px; }
.sf-concept-visual--sound span:nth-child(3),
.sf-concept-visual--sound span:nth-child(5),
.sf-concept-visual--ear span:nth-child(3),
.sf-concept-visual--ear span:nth-child(5) { height: 88px; background: var(--sf-coral); }
.sf-concept-visual--sound span:nth-child(4),
.sf-concept-visual--ear span:nth-child(4) { height: 118px; }

.sf-concept-visual--staff {
    background: repeating-linear-gradient(to bottom, #fff 0 2px, transparent 2px 22px), #eef2f7;
}

.sf-concept-visual--staff span {
    background: var(--sf-blue-dark);
    transform: rotate(-14deg);
}

.sf-concept-visual--keyboard {
    align-items: stretch;
    gap: 2px;
    background: #65758b;
}

.sf-concept-visual--keyboard span {
    width: 28px;
    height: auto;
    border-radius: 0 0 0.3rem 0.3rem;
}

.sf-concept-visual--keyboard span:nth-child(4) {
    background: var(--sf-coral);
}

.sf-concept-visual--rhythm span {
    width: 28px;
    border-radius: 0.2rem;
}

.sf-concept-visual--rhythm span:nth-child(1),
.sf-concept-visual--rhythm span:nth-child(5) {
    height: 78px;
    background: var(--sf-coral);
}

.sf-concept-visual--scale span {
    transform: translateY(calc((4 - var(--degree, 4)) * 7px));
}

.sf-concept-visual--scale span:nth-child(1) { transform: translateY(28px); }
.sf-concept-visual--scale span:nth-child(2) { transform: translateY(18px); }
.sf-concept-visual--scale span:nth-child(3) { transform: translateY(8px); }
.sf-concept-visual--scale span:nth-child(5) { transform: translateY(-8px); }
.sf-concept-visual--scale span:nth-child(6) { transform: translateY(-18px); }
.sf-concept-visual--scale span:nth-child(7) { transform: translateY(-28px); background: var(--sf-coral); }

.sf-concept-visual--circle span {
    position: absolute;
    transform: rotate(calc(var(--position, 0) * 51.4deg)) translateY(-52px);
}
.sf-concept-visual--circle span:nth-child(1) { --position: 0; }
.sf-concept-visual--circle span:nth-child(2) { --position: 1; }
.sf-concept-visual--circle span:nth-child(3) { --position: 2; }
.sf-concept-visual--circle span:nth-child(4) { --position: 3; background: var(--sf-coral); }
.sf-concept-visual--circle span:nth-child(5) { --position: 4; }
.sf-concept-visual--circle span:nth-child(6) { --position: 5; }
.sf-concept-visual--circle span:nth-child(7) { --position: 6; }

.sf-concept-visual--interval span,
.sf-concept-visual--chord span,
.sf-concept-visual--harmony span {
    position: absolute;
}

.sf-concept-visual--interval span:nth-child(n+3) { display: none; }
.sf-concept-visual--interval span:nth-child(1) { transform: translate(-48px, 30px); }
.sf-concept-visual--interval span:nth-child(2) { transform: translate(48px, -30px); background: var(--sf-coral); }

.sf-concept-visual--chord span:nth-child(n+5) { display: none; }
.sf-concept-visual--chord span:nth-child(1) { transform: translateY(48px); }
.sf-concept-visual--chord span:nth-child(2) { transform: translateY(16px); }
.sf-concept-visual--chord span:nth-child(3) { transform: translateY(-16px); background: var(--sf-coral); }
.sf-concept-visual--chord span:nth-child(4) { transform: translateY(-48px); }

.sf-concept-visual--harmony span:nth-child(1) { transform: translate(-74px, 24px); }
.sf-concept-visual--harmony span:nth-child(2) { transform: translate(-42px, -20px); }
.sf-concept-visual--harmony span:nth-child(3) { transform: translate(-10px, 24px); }
.sf-concept-visual--harmony span:nth-child(4) { transform: translate(22px, -20px); background: var(--sf-coral); }
.sf-concept-visual--harmony span:nth-child(5) { transform: translate(54px, 24px); }
.sf-concept-visual--harmony span:nth-child(n+6) { display: none; }

.sf-guided-practice__question {
    display: grid;
    gap: 0.6rem;
    border: 0;
    margin: 0;
    padding: 0;
}

.sf-guided-practice__question legend {
    margin-bottom: 0.45rem;
    font-size: 1.05rem;
    font-weight: 900;
    line-height: 1.5;
}

.sf-guided-practice__question label {
    display: flex;
    gap: 0.65rem;
    align-items: flex-start;
    border: 1px solid var(--sf-line);
    border-radius: 0.75rem;
    padding: 0.75rem 0.9rem;
    background: #fff;
    cursor: pointer;
}

.sf-guided-practice__question .sf-check-button {
    width: max-content;
    margin-top: 0.4rem;
}

.sf-guided-practice__transfer {
    margin-top: 1.25rem;
    border-top: 1px solid #c7d6e6;
    padding-top: 1rem;
}

.sf-guided-practice__transfer summary {
    color: var(--sf-blue-dark);
    font-weight: 900;
    cursor: pointer;
}

.sf-guided-practice__transfer details {
    margin-top: 0.7rem;
    border-left: 3px solid var(--sf-coral);
    padding-left: 0.8rem;
}

.sf-audio-warning {
    border-left: 3px solid #e2a43b;
    padding-left: 0.8rem;
    color: var(--sf-muted);
    font-size: 0.9rem !important;
}

.sf-exercise-list,
.sf-quiz {
    display: grid;
    gap: 1rem;
}

.sf-audio-exercise,
.sf-question {
    border: 1px solid var(--sf-line);
    border-radius: 1rem;
    padding: 1.25rem;
    background: #fff;
}

.sf-exercise-heading {
    justify-content: flex-start;
    align-items: flex-start;
}

.sf-exercise-heading > span,
.sf-question legend > span {
    display: inline-grid;
    width: 2rem;
    height: 2rem;
    flex: 0 0 2rem;
    place-items: center;
    border-radius: 50%;
    background: var(--sf-blue);
    color: #fff;
    font-size: 0.78rem;
    font-weight: 800;
}

.sf-exercise-heading h3 {
    margin: 0;
    font-size: 1.15rem;
}

.sf-exercise-heading p {
    margin: 0.35rem 0 0;
    color: var(--sf-muted);
}

.sf-audio-button {
    margin: 1rem 0;
    background: var(--sf-blue);
}

.sf-audio-button[disabled] {
    opacity: 0.7;
    cursor: wait;
}

.sf-audio-exercise fieldset,
.sf-question {
    min-width: 0;
}

.sf-audio-exercise fieldset {
    display: flex;
    flex-wrap: wrap;
    gap: 0.6rem;
    border: 0;
    margin: 0 0 1rem;
    padding: 0;
}

.sf-audio-exercise label,
.sf-question label {
    display: flex;
    align-items: flex-start;
    gap: 0.65rem;
    border: 1px solid var(--sf-line);
    border-radius: 0.75rem;
    padding: 0.75rem 0.9rem;
    cursor: pointer;
}

.sf-audio-exercise label:hover,
.sf-question label:hover {
    border-color: var(--sf-blue);
    background: #f5f8fc;
}

.sf-check-button {
    min-height: 40px;
    padding: 0.55rem 0.85rem;
    background: transparent;
    color: var(--sf-blue);
    box-shadow: inset 0 0 0 2px var(--sf-blue);
}

.sf-check-button:hover {
    background: var(--sf-blue);
}

.sf-feedback {
    min-height: 1.5em;
    margin: 0.75rem 0 0;
    color: var(--sf-muted);
    font-size: 0.9rem;
}

.sf-feedback.is-correct {
    color: var(--sf-success);
    font-weight: 700;
}

.sf-feedback.is-incorrect {
    color: var(--sf-error);
    font-weight: 700;
}

.sf-question {
    margin: 0;
}

.sf-question legend {
    display: flex;
    width: 100%;
    align-items: flex-start;
    gap: 0.75rem;
    margin-bottom: 1rem;
    color: var(--sf-ink);
    font-size: 1.05rem;
    font-weight: 800;
    line-height: 1.45;
}

.sf-question label {
    margin: 0.55rem 0;
}

.sf-question.is-correct {
    border-color: #78b99a;
}

.sf-question.is-incorrect {
    border-color: #d88d8d;
}

.sf-quiz-result {
    border-radius: 0.8rem;
    padding: 0;
    font-weight: 800;
}

.sf-quiz-result:not(:empty) {
    border: 1px solid var(--sf-line);
    padding: 1rem;
    background: #fff;
}

.sf-recap {
    border-radius: 1.2rem;
    padding: 1.6rem;
    background: var(--sf-mint);
}

.sf-sources {
    margin: 0 0 3rem;
    border-top: 1px solid var(--sf-line);
    border-bottom: 1px solid var(--sf-line);
    padding: 1rem 0;
}

.sf-sources summary {
    color: var(--sf-blue);
    font-weight: 800;
    cursor: pointer;
}

.sf-sources .sf-richtext {
    margin-top: 1rem;
    color: var(--sf-muted);
    font-size: 0.9rem;
}

.sf-lesson-nav {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    border-top: 1px solid var(--sf-line);
    padding-top: 1.5rem;
}

.sf-lesson-nav a {
    color: var(--sf-blue);
    font-weight: 800;
}

.sf-download-list {
    padding-left: 1.2rem;
}

.sf-tritone-lab {
    border: 1px solid #cbd8e7;
    border-radius: 1.5rem;
    margin-right: clamp(-1rem, -4vw, -4rem);
    margin-left: clamp(-1rem, -4vw, -4rem);
    padding: clamp(1rem, 4vw, 3rem);
    background:
        radial-gradient(circle at 94% 3%, rgba(231, 93, 85, 0.14), transparent 20rem),
        #f4f8fc;
}

.sf-lab-header {
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto;
    gap: 2rem;
    align-items: start;
}

.sf-lab-header h2 {
    margin-bottom: 0.6rem;
}

.sf-lab-header > div > p:last-child {
    max-width: 650px;
    margin: 0;
    color: var(--sf-muted);
    line-height: 1.65;
}

.sf-lab-score {
    display: grid;
    min-width: 135px;
    border-radius: 1rem;
    padding: 1rem;
    background: var(--sf-blue-dark);
    color: #fff;
    text-align: center;
}

.sf-lab-score span {
    color: rgba(255, 255, 255, 0.72);
    font-size: 0.75rem;
}

.sf-lab-score strong {
    font-size: 2rem;
}

.sf-lab-nav {
    display: flex;
    overflow-x: auto;
    gap: 0.5rem;
    margin: 1.75rem 0 1rem;
    padding: 0.35rem 0 0.6rem;
    scrollbar-width: thin;
}

.sf-lab-nav a {
    flex: 0 0 auto;
    border: 1px solid var(--sf-line);
    border-radius: 999px;
    padding: 0.5rem 0.75rem;
    background: #fff;
    color: var(--sf-blue);
    font-size: 0.82rem;
    font-weight: 800;
    text-decoration: none;
}

.sf-lab-prerequisites {
    border-left: 4px solid #e2a43b;
    padding: 0.75rem 1rem;
    background: #fff9eb;
}

.sf-lab-prerequisites summary {
    font-weight: 800;
    cursor: pointer;
}

.sf-lab-prerequisites p {
    margin-bottom: 0;
    color: var(--sf-muted);
    line-height: 1.6;
}

.sf-lab-prerequisites a,
.sf-lab-station a,
.sf-terminology-note a {
    color: var(--sf-blue);
    font-weight: 800;
}

.sf-lab-station {
    border-top: 1px solid #cbd8e7;
    padding: 3rem 0 0;
    margin-top: 3rem;
    scroll-margin-top: 1rem;
}

.sf-lab-station > p {
    max-width: 720px;
    color: var(--sf-muted);
    line-height: 1.7;
}

.sf-station-heading {
    display: flex;
    gap: 1rem;
    align-items: flex-start;
}

.sf-station-heading > span {
    display: grid;
    width: 2.65rem;
    height: 2.65rem;
    flex: 0 0 2.65rem;
    place-items: center;
    border-radius: 0.85rem;
    background: var(--sf-coral);
    color: #fff;
    font-size: 0.82rem;
    font-weight: 900;
}

.sf-station-heading .sf-kicker {
    margin-bottom: 0.25rem;
}

.sf-station-heading h3 {
    margin: 0;
    color: var(--sf-ink);
    font-size: clamp(1.4rem, 3vw, 2rem);
}

.sf-microscope,
.sf-staff-card,
.sf-mode-explorer,
.sf-resolution-stage,
.sf-chord-visual,
.sf-ear-game,
.sf-dictation,
.sf-error-case,
.sf-score-spotlight {
    border: 1px solid var(--sf-line);
    border-radius: 1rem;
    padding: clamp(1rem, 3vw, 1.5rem);
    background: #fff;
}

.sf-microscope {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 150px;
    gap: 1.5rem;
    align-items: center;
}

.sf-keyboard {
    position: relative;
    display: grid;
    height: 170px;
    grid-template-columns: repeat(8, minmax(44px, 1fr));
    overflow-x: auto;
    border: 1px solid #79869a;
    border-radius: 0.5rem;
    background: #d3dae3;
}

.sf-piano-key {
    display: flex;
    align-items: flex-end;
    justify-content: center;
    box-sizing: border-box;
    padding: 0.4rem 0.15rem;
    font-size: 0.68rem;
}

.sf-piano-key--white {
    min-width: 44px;
    border-right: 1px solid #8f99a7;
    background: #fff;
    color: var(--sf-ink);
}

.sf-piano-key--black {
    position: absolute;
    z-index: 2;
    top: 0;
    width: 36px;
    height: 62%;
    align-items: flex-end;
    border-radius: 0 0 0.3rem 0.3rem;
    background: #202633;
    color: #fff;
    box-shadow: 0 4px 7px rgba(0, 0, 0, 0.28);
}

.sf-piano-key.is-root,
.sf-piano-key.is-tritone {
    background: var(--sf-coral);
    color: #fff;
}

.sf-step-counter {
    display: grid;
    text-align: center;
}

.sf-step-counter strong {
    color: var(--sf-blue);
    font: 700 4.5rem/1 Georgia, serif;
}

.sf-step-counter span {
    color: var(--sf-muted);
    font-weight: 800;
}

.sf-inline-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 0.65rem;
    margin: 1rem 0;
}

.sf-secondary-button,
.sf-mini-task button,
.sf-mode-tabs button,
.sf-chord-switcher button,
.sf-note-palette button {
    min-height: 44px;
    border: 1px solid var(--sf-blue);
    border-radius: 0.75rem;
    padding: 0.65rem 0.85rem;
    background: #fff;
    color: var(--sf-blue);
    font: inherit;
    font-weight: 800;
    cursor: pointer;
}

.sf-secondary-button:hover,
.sf-secondary-button:focus-visible,
.sf-mini-task button:hover,
.sf-mini-task button:focus-visible,
.sf-mode-tabs button:hover,
.sf-mode-tabs button:focus-visible,
.sf-chord-switcher button:hover,
.sf-chord-switcher button:focus-visible,
.sf-note-palette button:hover,
.sf-note-palette button:focus-visible,
.sf-lab-nav a:focus-visible {
    outline: 3px solid #ffbf47;
    outline-offset: 2px;
}

.sf-lab-note,
.sf-terminology-note {
    border-left: 4px solid var(--sf-blue);
    padding: 0.75rem 1rem;
    background: #edf5fd;
    color: var(--sf-muted);
    line-height: 1.6;
}

.sf-staff-card {
    overflow: hidden;
}

.sf-staff {
    display: block;
    width: 100%;
    min-width: 360px;
    color: var(--sf-ink);
}

.sf-staff-lines line {
    stroke: #566174;
    stroke-width: 2;
}

.sf-staff ellipse {
    fill: var(--sf-blue-dark);
}

.sf-staff text {
    fill: var(--sf-ink);
    font: 700 16px system-ui, sans-serif;
}

.sf-staff .sf-clef {
    font: 72px Georgia, serif;
}

.sf-staff-answer {
    border-radius: 999px;
    margin: 0 auto;
    padding: 0.6rem 1rem;
    background: var(--sf-blue-dark);
    color: #fff;
    font-weight: 800;
    text-align: center;
}

.sf-mini-task,
.sf-ear-game fieldset {
    display: flex;
    flex-wrap: wrap;
    gap: 0.65rem;
    border: 0;
    margin: 1rem 0 0;
    padding: 0;
}

.sf-mini-task legend,
.sf-ear-game legend {
    width: 100%;
    margin-bottom: 0.4rem;
    font-weight: 800;
}

.sf-mini-task .sf-feedback,
.sf-ear-game .sf-feedback {
    width: 100%;
}

.sf-mini-task button.is-correct,
.sf-ear-game button.is-correct {
    border-color: var(--sf-success);
    background: var(--sf-mint);
    color: var(--sf-success);
}

.sf-mini-task button.is-incorrect,
.sf-ear-game button.is-incorrect {
    border-color: var(--sf-error);
    background: #fff0f0;
    color: var(--sf-error);
}

.sf-mode-tabs,
.sf-chord-switcher {
    display: flex;
    flex-wrap: wrap;
    gap: 0.55rem;
    margin: 1rem 0;
}

.sf-mode-tabs {
    display: grid;
    gap: 0.85rem;
}

.sf-mode-group {
    display: flex;
    flex-wrap: wrap;
    gap: 0.55rem;
}

.sf-mode-group--advanced {
    border: 1px solid #d8c7e7;
    border-radius: 0.85rem;
    padding: 0.8rem;
    background: #fcf9ff;
}

.sf-mode-group--advanced summary {
    flex-basis: 100%;
    width: 100%;
    color: var(--sf-blue-dark);
    font-weight: 900;
}

.sf-mode-group--advanced summary small {
    display: block;
    margin-top: 0.2rem;
    color: var(--sf-muted);
    font-weight: 600;
}

.sf-mode-group--advanced > p {
    flex-basis: 100%;
    color: var(--sf-muted);
    line-height: 1.55;
}

.sf-scale-direction {
    margin-top: 0;
    color: var(--sf-muted);
    font-size: 0.85rem;
}

.sf-station-advanced {
    margin-top: 1rem;
    border: 1px solid #d8c7e7;
    border-radius: 1rem;
    padding: 1rem;
    background: #fcf9ff;
}

.sf-station-advanced > summary {
    display: grid;
    gap: 0.2rem;
    color: var(--sf-blue-dark);
}

.sf-station-advanced > summary span {
    color: var(--sf-muted);
    font-weight: 600;
}

.sf-station-advanced[open] > summary {
    margin-bottom: 1rem;
}

.sf-mode-group__label {
    flex-basis: 100%;
    color: var(--sf-muted);
    font-size: 0.75rem;
    font-weight: 800;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.sf-mode-tabs button.is-active,
.sf-chord-switcher button.is-active {
    background: var(--sf-blue);
    color: #fff;
}

.sf-scale-strip {
    display: grid;
    grid-template-columns: repeat(7, minmax(58px, 1fr));
    overflow-x: auto;
    gap: 0.4rem;
    padding-bottom: 0.4rem;
}

.sf-scale-strip span {
    display: grid;
    min-width: 58px;
    place-items: center;
    border-radius: 0.75rem;
    padding: 0.65rem 0.25rem;
    background: var(--sf-cream);
}

.sf-scale-strip span.is-altered {
    border: 2px solid var(--sf-coral);
    background: #fff2ef;
}

.sf-scale-strip small {
    color: var(--sf-muted);
}

.sf-mode-summary {
    color: var(--sf-muted);
    line-height: 1.55;
}

.sf-melodic-context {
    margin: 1rem 0 0;
    border-left: 4px solid var(--sf-coral);
    padding: 0.8rem 1rem;
    background: #fff7ef;
    color: var(--sf-ink);
    line-height: 1.55;
}

.sf-pair-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.75rem;
}

.sf-pair-card {
    display: grid;
    min-height: 150px;
    gap: 0.35rem;
    border: 2px solid var(--sf-line);
    border-radius: 0.9rem;
    padding: 1rem;
    background: #fff;
    color: var(--sf-ink);
    font: inherit;
    text-align: left;
    cursor: pointer;
}

.sf-pair-card:hover,
.sf-pair-card:focus-visible,
.sf-pair-card.is-active {
    border-color: var(--sf-blue);
    outline: none;
}

.sf-pair-card span {
    color: var(--sf-coral);
    font-size: 0.78rem;
    font-weight: 900;
    text-transform: uppercase;
}

.sf-pair-card strong {
    font-size: 1.35rem;
}

.sf-pair-card small {
    color: var(--sf-muted);
    line-height: 1.55;
}

.sf-terminology-note {
    margin-top: 1rem;
}

.sf-resolution-stage {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: 1rem;
    align-items: center;
}

.sf-resolution-stage > div {
    display: grid;
    gap: 0.35rem;
    border-radius: 0.8rem;
    padding: 1rem;
    background: var(--sf-cream);
    text-align: center;
}

.sf-stage-label {
    color: var(--sf-muted);
    font-size: 0.75rem;
    font-weight: 800;
    text-transform: uppercase;
}

.sf-resolution-arrow {
    color: var(--sf-coral);
    font-size: 2rem;
}

.sf-chord-notes {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.sf-chord-notes span {
    display: grid;
    min-width: 54px;
    min-height: 54px;
    place-items: center;
    border: 2px solid var(--sf-line);
    border-radius: 50%;
    background: #fff;
    font-weight: 900;
}

.sf-chord-notes span.is-tritone-a {
    border-style: dashed;
    border-color: var(--sf-coral);
    background: #fff2ef;
}

.sf-chord-notes span.is-tritone-b {
    border-style: double;
    border-width: 4px;
    border-color: var(--sf-blue);
    background: #edf5fd;
}

.sf-chord-visual p {
    margin-bottom: 0;
    color: var(--sf-muted);
}

.sf-dictation,
.sf-builder,
.sf-transposition,
.sf-score-spotlight {
    margin-top: 1rem;
}

.sf-dictation h4,
.sf-builder h4,
.sf-transposition h4,
.sf-score-spotlight h4 {
    margin: 0.2rem 0 0.5rem;
    font-size: 1.2rem;
}

.sf-dictation > p,
.sf-builder > p,
.sf-transposition > p,
.sf-score-spotlight > p {
    color: var(--sf-muted);
    line-height: 1.6;
}

.sf-note-palette {
    display: flex;
    flex-wrap: wrap;
    gap: 0.45rem;
    margin: 0.8rem 0;
}

.sf-builder,
.sf-transposition {
    border: 1px solid var(--sf-line);
    border-radius: 1rem;
    padding: clamp(1rem, 3vw, 1.5rem);
    background: #fff;
}

.sf-builder-row {
    display: flex;
    flex-wrap: wrap;
    gap: 0.55rem;
    align-items: center;
}

.sf-builder-root {
    display: grid;
    min-width: 54px;
    min-height: 44px;
    place-items: center;
    border-radius: 0.7rem;
    background: var(--sf-blue-dark);
    color: #fff;
    font-weight: 900;
}

.sf-builder-row button,
[data-transposition-options] button,
[data-error-case] button {
    min-height: 44px;
    border: 1px solid var(--sf-blue);
    border-radius: 0.75rem;
    padding: 0.65rem 0.85rem;
    background: #fff;
    color: var(--sf-blue);
    font: inherit;
    font-weight: 800;
    cursor: pointer;
}

.sf-builder-row button:focus-visible,
[data-transposition-options] button:focus-visible,
[data-error-case] button:focus-visible {
    outline: 3px solid #ffbf47;
    outline-offset: 2px;
}

.sf-builder-row button.is-correct,
[data-transposition-options] button.is-correct,
[data-error-case] button.is-correct {
    border-color: var(--sf-success);
    background: var(--sf-mint);
    color: var(--sf-success);
}

.sf-builder-row button.is-incorrect,
[data-transposition-options] button.is-incorrect,
[data-error-case] button.is-incorrect {
    border-color: var(--sf-error);
    background: #fff0f0;
    color: var(--sf-error);
}

.sf-ear-progress {
    margin: 0;
    color: var(--sf-muted);
    font-size: 0.85rem;
    font-weight: 700;
}

.sf-dictation-entry {
    min-height: 1.7rem;
}

.sf-error-case {
    border-left: 5px solid var(--sf-coral);
}

.sf-error-case p,
.sf-error-case li {
    line-height: 1.6;
}

.sf-mastery-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.6rem;
    margin: 1rem 0;
}

.sf-mastery-grid span {
    display: grid;
    gap: 0.2rem;
    border: 1px solid var(--sf-line);
    border-radius: 0.8rem;
    padding: 0.9rem;
    background: #fff;
    font-weight: 800;
}

.sf-mastery-grid span b {
    color: var(--sf-muted);
    font-size: 0.76rem;
}

.sf-mastery-grid span.is-complete {
    border-color: #78b99a;
    background: var(--sf-mint);
}

.sf-mastery-grid span.is-complete b,
.sf-lab-complete.is-complete {
    color: var(--sf-success);
}

.sf-lab-complete {
    font-weight: 800;
}

.sr-only {
    position: absolute !important;
    width: 1px !important;
    height: 1px !important;
    overflow: hidden !important;
    clip: rect(0, 0, 0, 0) !important;
    white-space: nowrap !important;
}

@media (max-width: 760px) {
    .sf-module-grid,
    .sf-point-grid,
    .sf-flashcards,
    .sf-toc-links,
    .sf-learning-links,
    .sf-symbol-legend dl {
        grid-template-columns: 1fr;
    }

    .sf-start-card {
        align-items: stretch;
        flex-direction: column;
    }

    .sf-lesson-card {
        grid-template-columns: 1fr auto;
    }

    .sf-lesson-card strong,
    .sf-lesson-state {
        grid-column: 1 / -1;
    }

    .sf-interactive-section {
        margin-right: -0.5rem;
        margin-left: -0.5rem;
    }

    .sf-topic {
        grid-template-columns: 1fr;
    }

    .sf-topic > span {
        width: max-content;
    }

    .sf-lesson-nav {
        flex-direction: column;
    }

    .sf-tritone-lab {
        margin-right: -0.5rem;
        margin-left: -0.5rem;
    }

    .sf-guided-practice {
        margin-right: -0.5rem;
        margin-left: -0.5rem;
    }

    .sf-guided-practice__header,
    .sf-guided-practice__observe {
        grid-template-columns: 1fr;
    }

    .sf-guided-practice__header {
        display: grid;
    }

    .sf-guided-practice__state {
        width: max-content;
    }

    .sf-lab-header,
    .sf-microscope,
    .sf-pair-grid,
    .sf-mastery-grid {
        grid-template-columns: 1fr;
    }

    .sf-lab-score {
        width: 100%;
        box-sizing: border-box;
    }

    .sf-resolution-stage {
        grid-template-columns: 1fr;
    }

    .sf-resolution-arrow {
        transform: rotate(90deg);
        text-align: center;
    }

    .sf-staff-card {
        overflow-x: auto;
    }
}

@media (prefers-reduced-motion: reduce) {
    .sf-module-card,
    .sf-tritone-lab *,
    .sf-resolution-arrow {
        transition: none;
        animation: none;
    }
}