/* =========================================================================
   课程版块（练习室共用）· course.css
   三层视图：① 课程列表  ② 课程详情（章节 + 课时）  ③ 课时（谱面 + 要点）
   视觉沿用练习室既有语言：卡片 20 / 控件 12 / 胶囊 999，一道发丝线、一个蓝。
   颜色全部取练习室 CSS 变量，浅色深色自动跟随。
   ========================================================================= */

/* ---------- 四个板块的分段控件收紧一点 ---------- */
.seg[data-tab] .seg-btn { padding-left: 8px; padding-right: 8px; }
@media (max-width: 640px) {
    .seg[data-tab] .seg-btn { gap: 3px; padding: 8px 4px; }
    .seg[data-tab] .seg-btn svg { width: 14px; height: 14px; }
    .seg[data-tab] .seg-tx { font-size: 11.5px; letter-spacing: 0; }
}

/* ---------- 通用 ---------- */
#paneCourse { animation: panel-in .5s var(--ease) both; }
.crs-view { min-height: 120px; }
.crs-btn {
    display: inline-flex; align-items: center; justify-content: center; gap: 6px;
    border: 1px solid transparent; border-radius: 999px; padding: 8px 16px;
    font-family: var(--font); font-size: 13px; font-weight: 600; cursor: pointer;
    background: var(--tint); color: var(--ink); white-space: nowrap;
    transition: background .16s ease, color .16s ease, transform .12s var(--ease), box-shadow .16s ease;
}
.crs-btn:hover { background: var(--tint-2); }
.crs-btn:active { transform: scale(.975); }
.crs-btn.primary { background: var(--blue); color: #fff; box-shadow: 0 1px 2px rgba(0, 113, 227, .25), 0 6px 16px rgba(0, 113, 227, .22); }
.crs-btn.primary:hover { filter: brightness(1.06); }
.crs-btn.primary:disabled { opacity: .55; cursor: default; filter: none; }
.crs-btn.ghost { background: transparent; border-color: var(--line-2); color: var(--ink-2); }
.crs-btn.ghost:hover { color: var(--blue); border-color: var(--blue); background: var(--blue-soft); }
.crs-btn[disabled] { opacity: .4; pointer-events: none; }
.crs-back {
    display: inline-flex; align-items: center; gap: 5px; border: 0; background: transparent;
    color: var(--ink-2); font-family: var(--font); font-size: 13px; font-weight: 500;
    padding: 4px 8px 4px 0; margin-bottom: 10px; cursor: pointer; border-radius: 999px;
    transition: color .15s ease;
}
.crs-back:hover { color: var(--blue); }
.crs-back svg { width: 14px; height: 14px; }

/* =========================================================================
   ① 课程列表
   ========================================================================= */
.crs-head {
    display: flex; align-items: flex-end; gap: 18px;
    padding: 2px 4px 16px;
}
.crs-h { margin: 0; font-size: 26px; font-weight: 700; letter-spacing: -.025em; color: var(--ink); }
.crs-sub { margin: 7px 0 0; font-size: 13px; line-height: 1.55; color: var(--ink-2); }
.crs-stat { margin-left: auto; text-align: right; font-size: 12px; color: var(--ink-3); white-space: nowrap; }
.crs-stat b { display: block; font-size: 22px; font-weight: 700; color: var(--ink); letter-spacing: -.02em; font-variant-numeric: tabular-nums; line-height: 1.15; }

.crs-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px; }
@media (max-width: 760px) { .crs-grid { grid-template-columns: 1fr; } }

.crs-card {
    display: flex; flex-direction: column; text-align: left; padding: 0; overflow: hidden;
    background: var(--card); border: 1px solid var(--line); border-radius: var(--r-card);
    box-shadow: var(--sh-1); cursor: pointer; font-family: var(--font); color: var(--ink);
    transition: transform .28s var(--ease), box-shadow .28s var(--ease), border-color .2s ease;
}
.crs-card:hover { transform: translateY(-3px); box-shadow: var(--sh-2); border-color: var(--line-2); }
.crs-card:active { transform: translateY(-1px) scale(.997); }

.crs-cover {
    position: relative; height: 136px; overflow: hidden;
    background: linear-gradient(135deg, #eef1f7 0%, #e2e7f1 60%, #dbe3f0 100%);
}
[data-theme="dark"] .crs-cover { background: linear-gradient(135deg, #26262a 0%, #1e1e21 100%); }
.crs-cover img {
    width: 100%; height: 100%; object-fit: cover; object-position: 50% 8%;
    display: block; opacity: .96; transform: scale(1.001);
    transition: transform .5s var(--ease);
}
.crs-card:hover .crs-cover img { transform: scale(1.03); }
.crs-cover::after {
    content: ''; position: absolute; inset: 0; pointer-events: none;
    background: linear-gradient(to bottom, rgba(255, 255, 255, 0) 46%, rgba(255, 255, 255, .72) 100%);
}
[data-theme="dark"] .crs-cover::after {
    background: linear-gradient(to bottom, rgba(28, 28, 30, 0) 46%, rgba(28, 28, 30, .78) 100%);
}
.crs-cover .crs-fallback {
    position: absolute; inset: 0; display: flex; align-items: center; justify-content: center;
    color: var(--ink-3);
}
.crs-cover .crs-fallback svg { width: 44px; height: 44px; opacity: .45; }
.crs-lv {
    position: absolute; left: 12px; top: 12px; z-index: 2;
    padding: 3px 9px 4px; border-radius: 999px;
    background: rgba(255, 255, 255, .82); color: var(--ink);
    -webkit-backdrop-filter: blur(10px); backdrop-filter: blur(10px);
    font-size: 11px; font-weight: 600; letter-spacing: .02em;
    box-shadow: 0 1px 2px rgba(0, 0, 0, .08);
}
[data-theme="dark"] .crs-lv { background: rgba(40, 40, 44, .86); color: #f5f5f7; }
.crs-lv.sample { left: auto; right: 12px; color: var(--ink-3); font-weight: 500; }

.crs-body { display: flex; flex-direction: column; gap: 5px; padding: 12px 14px 13px; flex: 1 1 auto; }
.crs-title { font-size: 16px; font-weight: 700; letter-spacing: -.015em; line-height: 1.3; }
.crs-desc {
    font-size: 12.5px; line-height: 1.55; color: var(--ink-2);
    display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden;
}
.crs-meta { display: flex; align-items: center; gap: 9px; margin-top: 9px; font-size: 11.5px; color: var(--ink-3); font-variant-numeric: tabular-nums; }
.crs-wip { color: var(--ink-3); font-style: normal; }
.crs-views { display: inline-flex; align-items: center; gap: 4px; margin-left: auto; color: var(--ink-3); white-space: nowrap; }
.crs-views svg { width: 13px; height: 13px; opacity: .8; }
.crs-chip.views { display: inline-flex; align-items: center; gap: 4px; font-variant-numeric: tabular-nums; }
.crs-chip.views svg { width: 12px; height: 12px; opacity: .75; }
.crs-prog { flex: 1 1 auto; height: 4px; border-radius: 999px; background: var(--tint-2); overflow: hidden; }
.crs-prog i { display: block; height: 100%; width: 0; border-radius: 999px; background: var(--blue); transition: width .5s var(--ease); }

/* =========================================================================
   ② 课程详情
   ========================================================================= */
.crs-hero {
    display: flex; gap: 18px; align-items: stretch;
    padding: 16px; background: var(--card); border: 1px solid var(--line);
    border-radius: var(--r-card); box-shadow: var(--sh-1);
}
.crs-hero-cover {
    width: 148px; height: 148px; flex: 0 0 auto; border-radius: 16px; overflow: hidden;
    background: linear-gradient(135deg, #eef1f7, #dfe5ef); position: relative;
}
[data-theme="dark"] .crs-hero-cover { background: linear-gradient(135deg, #26262a, #1e1e21); }
.crs-hero-cover img { width: 100%; height: 100%; object-fit: cover; object-position: 50% 8%; display: block; }
.crs-hero-cover .crs-fallback { position: absolute; inset: 0; display: flex; align-items: center; justify-content: center; color: var(--ink-3); }
.crs-hero-cover .crs-fallback svg { width: 40px; height: 40px; opacity: .45; }

.crs-hero-main { flex: 1 1 auto; min-width: 0; display: flex; flex-direction: column; }
.crs-tags { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 8px; }
.crs-chip {
    padding: 3px 9px 4px; border-radius: 999px; background: var(--tint);
    font-size: 11px; font-weight: 500; color: var(--ink-2); white-space: nowrap;
}
.crs-chip.lv { background: var(--blue-soft); color: var(--blue); font-weight: 600; }
.crs-htitle { margin: 0; font-size: 21px; font-weight: 700; letter-spacing: -.022em; line-height: 1.28; }
.crs-hdesc { margin: 7px 0 0; font-size: 13px; line-height: 1.6; color: var(--ink-2); max-width: 60ch; }
.crs-hactions { display: flex; align-items: center; gap: 12px; margin-top: auto; padding-top: 14px; }
.crs-ring {
    --p: 0%;
    margin-left: auto; width: 52px; height: 52px; border-radius: 50%; flex: 0 0 auto;
    background: conic-gradient(var(--blue) var(--p), var(--tint-2) 0);
    display: grid; place-items: center; position: relative;
}
.crs-ring::before {
    content: ''; position: absolute; inset: 5px; border-radius: 50%; background: var(--card);
}
.crs-ring span {
    position: relative; font-size: 11.5px; font-weight: 700; color: var(--ink);
    font-variant-numeric: tabular-nums; letter-spacing: -.02em;
}

.crs-chap { margin-top: 18px; }
.crs-chap-h {
    display: flex; align-items: baseline; gap: 8px; margin: 0 4px 8px;
    font-size: 12px; font-weight: 600; letter-spacing: .03em; color: var(--ink-3);
}
.crs-chap-h .n { color: var(--ink-2); letter-spacing: .02em; }
.crs-rows {
    background: var(--card); border: 1px solid var(--line); border-radius: 16px;
    overflow: hidden; box-shadow: var(--sh-1);
}
.crs-row {
    display: flex; align-items: center; gap: 12px; width: 100%; padding: 12px 14px;
    border: 0; border-top: 1px solid var(--line); background: transparent;
    font-family: var(--font); color: var(--ink); text-align: left; cursor: pointer;
    transition: background .15s ease;
}
.crs-row:first-child { border-top: 0; }
.crs-row:hover { background: var(--tint); }
.crs-row:active { background: var(--tint-2); }
.crs-no {
    width: 26px; height: 26px; flex: 0 0 auto; border-radius: 50%;
    display: grid; place-items: center; font-size: 11.5px; font-weight: 700;
    background: var(--tint); color: var(--ink-2); font-variant-numeric: tabular-nums;
    transition: background .2s ease, color .2s ease, box-shadow .2s ease;
}
.crs-row.done .crs-no { background: var(--blue); color: #fff; }
.crs-row.now .crs-no { background: var(--blue-soft); color: var(--blue); box-shadow: inset 0 0 0 1.5px var(--blue); }
.crs-rt { flex: 1 1 auto; min-width: 0; }
.crs-rt b { display: block; font-size: 14px; font-weight: 600; letter-spacing: -.01em; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.crs-rt small { display: block; margin-top: 2px; font-size: 12px; color: var(--ink-3); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.crs-row.done .crs-rt b { color: var(--ink-2); }
.crs-min { flex: 0 0 auto; font-size: 11.5px; color: var(--ink-3); font-variant-numeric: tabular-nums; }
.crs-row .crs-go { flex: 0 0 auto; width: 16px; height: 16px; color: var(--ink-3); opacity: .5; }
.crs-row:hover .crs-go { color: var(--blue); opacity: 1; }
@media (max-width: 620px) {
    .crs-min { display: none; }
    .crs-hero { flex-direction: column; }
    .crs-hero-cover { width: 100%; height: 124px; }
    .crs-hactions { padding-top: 12px; }
}

/* =========================================================================
   ③ 课时（谱面 + 要点）
   ========================================================================= */
.crs-lbar { display: flex; align-items: center; gap: 10px; margin: 0 2px 10px; }
.crs-lbar .crs-back { margin-bottom: 0; }
.crs-lcrumb {
    font-size: 13px; font-weight: 600; color: var(--ink-2); min-width: 0;
    white-space: nowrap; overflow: hidden; text-overflow: ellipsis; flex: 1 1 auto;
}
.crs-lcrumb em { font-style: normal; color: var(--ink-3); font-weight: 400; }
.crs-lnav { display: flex; gap: 6px; flex: 0 0 auto; }
.crs-icon {
    width: 30px; height: 30px; border-radius: 999px; border: 1px solid transparent;
    background: var(--tint); color: var(--ink-2); cursor: pointer;
    display: inline-flex; align-items: center; justify-content: center;
    transition: background .15s ease, color .15s ease;
}
.crs-icon:hover { background: var(--blue-soft); color: var(--blue); }
.crs-icon[disabled] { opacity: .3; pointer-events: none; }
.crs-icon svg { width: 16px; height: 16px; }

.crs-lgrid { min-width: 0; }
.crs-lmain { min-width: 0; }
.crs-lmain > .viewer { margin: 0; }

/* 课程信息浮层 + 悬浮钮 */
.crs-sidefab {
    position: fixed; right: 14px; top: 50%; transform: translateY(-50%);
    z-index: 58; width: 42px; height: 42px; border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    background: var(--card); border: 1px solid var(--line);
    box-shadow: var(--sh-2); color: var(--blue); cursor: pointer;
    transition: background .15s, transform .15s;
}
.crs-sidefab:hover { background: var(--blue-soft); transform: translateY(-50%) scale(1.06); }
.crs-sidefab svg { width: 19px; height: 19px; pointer-events: none; }
.crs-lgrid.side-open + .crs-sidefab { display: none; }

.crs-side {
    display: none;
    background: var(--card); border: 1px solid var(--line); border-radius: var(--r-card);
    box-shadow: var(--sh-2); padding: 16px;
    position: fixed; right: 14px; top: 50%; transform: translateY(-50%);
    width: min(320px, calc(100vw - 72px));
    max-height: min(78vh, 640px); overflow: auto; z-index: 59;
}
.crs-lgrid.side-open + .crs-sidefab + .crs-side { display: block; }

/* 课时目录：对齐全站文章页（右侧目录卡 + 滚动高亮；窄屏收进正文顶部折叠块） */
.crs-lgrid.has-toc { display: grid; grid-template-columns: minmax(0, 1fr) 224px; gap: 26px; align-items: start; }
.crs-toc {
    position: sticky; top: 12px;
    background: var(--card); border: 1px solid var(--line); border-radius: var(--r-card);
    box-shadow: var(--sh-1); padding: 16px 0 10px;
    max-height: calc(100vh - 24px); overflow: auto;
    scrollbar-width: thin; scrollbar-color: var(--line) transparent;
}
.crs-toc h4 {
    margin: 0 16px 8px; font-size: 12px; font-weight: 700;
    letter-spacing: .06em; color: var(--ink-3); text-transform: uppercase;
}
.crs-toc ul, .crs-toc-m ul { list-style: none; margin: 0; padding: 0; }
.crs-toc button, .crs-toc-m button {
    display: block; width: 100%; text-align: left; border: none; background: none; cursor: pointer;
    font: inherit; font-size: 12.5px; line-height: 1.5; color: var(--ink-3);
    padding: 4px 12px 4px 15px; border-left: 2px solid transparent;
    transition: color .15s, border-color .15s, background .15s;
}
.crs-toc button.sub, .crs-toc-m button.sub { padding-left: 25px; }
.crs-toc button:hover, .crs-toc-m button:hover { color: var(--ink); }
.crs-toc button.active, .crs-toc-m button.active {
    color: var(--blue); border-left-color: var(--blue); background: var(--blue-soft);
}
[id^="lcs-sec-"] { scroll-margin-top: 76px; }
.crs-toc-m { display: none; }
@media (max-width: 940px) {
    .crs-lgrid.has-toc { display: block; }
    .crs-toc { display: none; }
    .crs-toc-m {
        display: block; margin: 0 0 18px;
        background: var(--card); border: 1px solid var(--line);
        border-radius: var(--r-card); box-shadow: var(--sh-1);
    }
    .crs-toc-m summary {
        list-style: none; display: flex; align-items: center; gap: 6px;
        padding: 11px 14px; font-size: 13px; font-weight: 650; color: var(--ink); cursor: pointer;
    }
    .crs-toc-m summary::-webkit-details-marker { display: none; }
    .crs-toc-m summary::after {
        content: ''; margin-left: auto; width: 7px; height: 7px;
        border-right: 1.6px solid var(--ink-3); border-bottom: 1.6px solid var(--ink-3);
        transform: rotate(45deg); transition: transform .15s;
    }
    .crs-toc-m[open] summary::after { transform: rotate(-135deg); }
    .crs-toc-m ul { padding: 2px 8px 10px; }
}
.crs-sideclose {
    position: absolute; top: 10px; right: 10px; width: 26px; height: 26px;
    display: flex; align-items: center; justify-content: center;
    border: none; background: transparent; color: var(--ink-3);
    border-radius: 50%; cursor: pointer;
}
.crs-sideclose:hover { background: var(--blue-soft); color: var(--blue); }
.crs-sideclose svg { width: 14px; height: 14px; pointer-events: none; }
.crs-stitle { padding-right: 26px; }
.crs-kicker {
    display: inline-flex; align-items: center; gap: 5px;
    font-size: 11px; font-weight: 700; letter-spacing: .06em; color: var(--blue);
    text-transform: uppercase; margin-bottom: 8px;
}
.crs-stitle { margin: 0 0 4px; font-size: 18px; font-weight: 700; letter-spacing: -.02em; line-height: 1.35; }
.crs-sdesc { margin: 0 0 14px; font-size: 12.5px; line-height: 1.6; color: var(--ink-2); }

.crs-block { border-top: 1px solid var(--line); padding-top: 12px; margin-top: 12px; }
.crs-block:first-of-type { border-top: 0; padding-top: 0; margin-top: 0; }
.crs-block-h {
    display: flex; align-items: center; gap: 6px; margin-bottom: 8px;
    font-size: 11.5px; font-weight: 700; letter-spacing: .04em; color: var(--ink-3);
}
.crs-points { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 7px; }
.crs-points li {
    position: relative; padding-left: 15px; font-size: 12.5px; line-height: 1.6; color: var(--ink);
}
.crs-points li::before {
    content: ''; position: absolute; left: 3px; top: .62em; width: 5px; height: 5px;
    border-radius: 50%; background: var(--blue); opacity: .7;
}
.crs-bpm {
    display: flex; align-items: baseline; gap: 6px;
    padding: 10px 12px; border-radius: 12px; background: var(--tint);
}
.crs-bpm span { font-size: 12px; color: var(--ink-2); }
.crs-bpm b { margin-left: auto; font-size: 22px; font-weight: 700; letter-spacing: -.03em; font-variant-numeric: tabular-nums; }
.crs-bpm i { font-style: normal; font-size: 11px; color: var(--ink-3); }
.crs-tip {
    font-size: 12px; line-height: 1.65; color: var(--ink-2);
    padding-left: 10px; border-left: 2px solid var(--line-2);
}
.crs-done {
    display: inline-flex; align-items: center; gap: 6px; width: 100%; justify-content: center;
    margin-top: 14px;
}
.crs-done.is-done { background: var(--blue-soft); color: var(--blue); box-shadow: none; }
.crs-side-tools { display: flex; gap: 8px; margin-top: 8px; }
.crs-side-tools .crs-btn { flex: 1 1 0; padding: 7px 10px; font-size: 12px; }
.crs-side-tools .crs-btn svg { width: 13px; height: 13px; }

/* =========================================================================
   ④ 图文互动课时（概念课与指板实验）
   ========================================================================= */
.crs-article {
    min-width: 0; padding: 30px; background: var(--card); border: 1px solid var(--line);
    border-radius: var(--r-card); box-shadow: var(--sh-1); color: var(--ink);
    font-size: 14px; line-height: 1.75;
}
.crs-article p { margin: 10px 0 0; max-width: 68ch; }
.crs-article b { font-weight: 650; }
.crs-content-loading, .crs-content-error {
    min-height: 240px; display: flex; flex-direction: column; align-items: center;
    justify-content: center; gap: 8px; color: var(--ink-3); text-align: center;
}
.crs-content-error b { color: var(--ink); }
.crs-content-error .crs-btn { margin-top: 8px; }
.lcs-hero { padding-bottom: 6px; }
.lcs-eyebrow {
    display: flex; align-items: center; gap: 10px; color: var(--blue);
    font-size: 11px; font-weight: 700; letter-spacing: .08em;
}
.lcs-eyebrow span {
    display: inline-grid; place-items: center; width: 26px; height: 26px;
    border: 1px solid var(--blue); border-radius: 50%; letter-spacing: 0;
}
.lcs-hero h2 {
    margin: 10px 0 0; color: var(--ink); font-size: clamp(22px, 3vw, 28px);
    font-weight: 750; line-height: 1.22; letter-spacing: -.03em;
}
.lcs-hero h2 span { color: var(--blue); }
.lcs-lead { margin-top: 16px !important; color: var(--ink-2); font-size: 14px; line-height: 1.8; }
.lcs-bigidea {
    display: flex; flex-direction: column; gap: 3px; margin-top: 20px; padding: 13px 16px;
    background: var(--blue-soft); border-left: 3px solid var(--blue); border-radius: 4px 12px 12px 4px;
}
.lcs-bigidea strong { color: var(--blue); font-size: 12px; }
.lcs-bigidea span { font-size: 13px; color: var(--ink); }
.lcs-section { margin-top: 30px; padding-top: 28px; border-top: 1px solid var(--line); }
.lcs-section:first-of-type { margin-top: 22px; padding-top: 0; border-top: 0; }
.lcs-sechead { display: flex; align-items: center; gap: 10px; margin-bottom: 12px; }
.lcs-sechead > span {
    flex: 0 0 auto; display: inline-grid; place-items: center; min-width: 28px; height: 24px;
    padding: 0 5px; border-radius: 7px; background: var(--tint); color: var(--blue);
    font-size: 11px; font-weight: 750; font-variant-numeric: tabular-nums;
}
.lcs-sechead h3 { margin: 0; font-size: 18px; font-weight: 700; line-height: 1.4; letter-spacing: -.02em; }
.lcs-distance-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; margin-top: 18px; }
.lcs-distance-card { padding: 16px; border: 1px solid var(--line); border-radius: 14px; background: var(--tint); }
.lcs-distance-title { display: flex; align-items: baseline; gap: 8px; }
.lcs-distance-title strong { font-size: 18px; }
.lcs-distance-title span { color: var(--ink-3); font-size: 11px; }
.lcs-distance-demo { display: flex; align-items: center; justify-content: center; gap: 13px; margin: 20px 0 12px; }
.lcs-distance-demo i {
    display: grid; place-items: center; width: 42px; height: 42px; border-radius: 50%;
    background: var(--card); color: var(--blue); border: 1px solid var(--line-2);
    font-style: normal; font-weight: 700; font-size: 16px;
}
.lcs-distance-demo span { color: var(--ink-3); font-size: 11px; }
.lcs-distance-card p { margin: 0; color: var(--ink-2); font-size: 12px; text-align: center; }
.lcs-rule { display: flex; flex-direction: column; gap: 2px; margin-top: 12px; padding: 12px 15px; border-radius: 12px; background: var(--tint); }
.lcs-rule strong { font-size: 13px; }
.lcs-rule span { color: var(--ink-2); font-size: 12px; }
.lcs-table-wrap { margin-top: 16px; overflow-x: auto; border: 1px solid var(--line); border-radius: 12px; }
.lcs-table { width: 100%; border-collapse: collapse; font-size: 12.5px; font-variant-numeric: tabular-nums; }
.lcs-table th, .lcs-table td { padding: 8px 13px; border-bottom: 1px solid var(--line); text-align: left; white-space: nowrap; }
.lcs-table th { background: var(--tint); color: var(--ink-3); font-size: 11px; font-weight: 650; }
.lcs-table td:first-child { color: var(--ink-3); }
.lcs-table td:nth-child(2) { color: var(--blue); font-weight: 700; }
.lcs-table tr:last-child td { border-bottom: 0; }
.lcs-note { padding-left: 12px; border-left: 2px solid var(--line-2); color: var(--ink-2); font-size: 12.5px; }
.lcs-lab { margin-top: 16px; padding: 16px; border: 1px solid var(--line); border-radius: 16px; background: var(--tint); }
.lcs-labbar { display: flex; align-items: center; justify-content: space-between; gap: 12px; }
.lcs-rootpick { display: flex; align-items: center; gap: 8px; color: var(--ink-2); font-size: 12px; font-weight: 650; }
.lcs-rootpick select {
    min-height: 40px; padding: 0 30px 0 11px; border: 1px solid var(--line-2); border-radius: 10px;
    background: var(--card); color: var(--ink); font-family: var(--font); font-size: 13px; cursor: pointer;
}
.lcs-sound { display: flex; gap: 6px; }
.lcs-sound button {
    min-height: 40px; padding: 0 12px; border: 1px solid var(--line-2); border-radius: 10px;
    background: var(--card); color: var(--ink-2); font-family: var(--font); font-size: 12px; cursor: pointer;
}
.lcs-sound button:hover { color: var(--blue); border-color: var(--blue); }
.lcs-choices { display: grid; grid-template-columns: repeat(7, minmax(0, 1fr)); gap: 6px; margin-top: 14px; }
.lcs-choices button {
    min-width: 0; min-height: 38px; padding: 4px; border: 1px solid var(--line); border-radius: 9px;
    background: var(--card); color: var(--ink-2); font-family: var(--font); font-size: 12px;
    font-weight: 650; cursor: pointer; transition: background .15s ease, color .15s ease, border-color .15s ease;
}
.lcs-choices button:hover { border-color: var(--blue); color: var(--blue); }
.lcs-choices button.on { background: var(--blue); border-color: var(--blue); color: #fff; }
.lcs-readout { display: flex; align-items: baseline; gap: 10px; margin-top: 15px; padding: 0 2px; }
.lcs-readout strong { font-size: 21px; letter-spacing: -.02em; }
.lcs-readout span { color: var(--ink-2); font-size: 12px; }
.lcs-board-scroll { margin-top: 12px; overflow-x: auto; border: 1px solid var(--line); border-radius: 12px; background: var(--card); }
.lcs-board { min-width: 630px; padding: 8px 0; }
.lcs-board-row { display: grid; grid-template-columns: 44px repeat(13, minmax(42px, 1fr)); align-items: center; }
.lcs-board-row > b { color: var(--ink-3); font-size: 11px; font-weight: 650; text-align: center; }
.lcs-board-head > span { height: 22px; color: var(--ink-3); font-size: 11px; text-align: center; font-variant-numeric: tabular-nums; }
.lcs-cell { position: relative; display: grid; place-items: center; height: 43px; border-right: 1px solid var(--line); }
.lcs-cell:last-child { border-right: 0; }
.lcs-cell::before { content: ''; position: absolute; left: 0; right: 0; top: 50%; height: 1px; background: var(--line-2); }
.lcs-cell i {
    position: relative; z-index: 1; display: grid; place-items: center; width: 28px; height: 28px;
    border-radius: 50%; background: var(--card); color: var(--ink-3); border: 1px solid transparent;
    font-style: normal; font-size: 10.5px; font-weight: 650;
}
.lcs-cell i.is-root { background: var(--blue); color: #fff; }
.lcs-cell i.is-target { background: #d85a30; color: #fff; }
.lcs-cell i.is-root.is-target { border: 3px solid var(--card); outline: 1px solid #d85a30; }
.lcs-legend { display: flex; align-items: center; gap: 14px; margin-top: 10px; color: var(--ink-2); font-size: 11px; }
.lcs-legend span { display: inline-flex; align-items: center; gap: 5px; }
.lcs-legend i { width: 9px; height: 9px; border-radius: 50%; }
.lcs-legend i.root { background: var(--blue); }
.lcs-legend i.target { background: #d85a30; }
.lcs-legend em { margin-left: auto; color: var(--ink-3); font-style: normal; }
.lcs-song-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 8px; margin-top: 16px; }
.lcs-song-grid > div { display: grid; grid-template-columns: 38px 1fr; column-gap: 8px; padding: 11px 12px; border-radius: 11px; background: var(--tint); }
.lcs-song-grid span { grid-row: 1 / 3; align-self: center; color: var(--blue); font-size: 15px; font-weight: 750; }
.lcs-song-grid strong { font-size: 12px; line-height: 1.4; }
.lcs-song-grid small { color: var(--ink-3); font-size: 11px; }
.lcs-earsteps, .lcs-practice ol { margin: 15px 0 0; padding-left: 22px; color: var(--ink-2); }
.lcs-earsteps li, .lcs-practice li { margin-top: 7px; padding-left: 4px; }
.lcs-score { margin-left: auto; color: var(--blue); font-size: 12px; font-variant-numeric: tabular-nums; }
.lcs-quiz { padding: 13px 0; border-bottom: 1px solid var(--line); }
.lcs-quiz:last-child { border-bottom: 0; }
.lcs-quiz p { margin: 0 0 10px; font-weight: 600; }
.lcs-quiz > div { display: flex; gap: 7px; }
.lcs-quiz button {
    min-width: 64px; min-height: 40px; border: 1px solid var(--line-2); border-radius: 10px;
    background: var(--tint); color: var(--ink); font-family: var(--font); font-weight: 650; cursor: pointer;
}
.lcs-quiz button:hover { border-color: var(--blue); color: var(--blue); }
.lcs-quiz button.correct { background: #18794e; border-color: #18794e; color: #fff; }
.lcs-quiz button.wrong { border-color: #b3261e; color: #b3261e; }
.lcs-quiz button:disabled { cursor: default; opacity: .65; }
.lcs-quiz button.correct:disabled { opacity: 1; }
.lcs-quiz small { display: block; min-height: 19px; margin-top: 6px; color: var(--ink-2); font-size: 11.5px; }
.lcs-check { display: flex; flex-direction: column; gap: 3px; margin-top: 18px; padding: 13px 15px; border-radius: 12px; background: var(--blue-soft); }
.lcs-check strong { color: var(--blue); font-size: 12px; }
.lcs-check span { font-size: 12.5px; }
.lcs-footer { margin-top: 28px; padding-top: 18px; border-top: 1px solid var(--line); color: var(--ink-3); font-size: 11.5px; }
.lcs-footer p { margin: 5px 0 0; }
[data-theme="dark"] .lcs-cell i.is-target { background: #f0997b; color: #2c2c2a; }
[data-theme="dark"] .lcs-cell i.is-root.is-target { outline-color: #f0997b; }
[data-theme="dark"] .lcs-quiz button.correct { background: #5dcaa5; border-color: #5dcaa5; color: #04342c; }
[data-theme="dark"] .lcs-quiz button.wrong { border-color: #f09595; color: #f09595; }
@media (max-width: 620px) {
    .crs-article { padding: 18px 15px; }
    .lcs-hero h2 { font-size: 34px; }
    .lcs-distance-grid { grid-template-columns: 1fr; }
    .lcs-lab { padding: 12px; }
    .lcs-labbar { align-items: flex-start; flex-direction: column; }
    .lcs-sound { width: 100%; }
    .lcs-sound button { flex: 1; min-height: 44px; }
    .lcs-rootpick select { min-height: 44px; }
    .lcs-choices { grid-template-columns: repeat(4, minmax(0, 1fr)); }
    .lcs-choices button, .lcs-quiz button { min-height: 44px; }
    .lcs-readout { align-items: flex-start; flex-direction: column; gap: 1px; }
    .lcs-legend { flex-wrap: wrap; gap: 8px 14px; }
    .lcs-legend em { width: 100%; margin-left: 0; }
    .lcs-song-grid { grid-template-columns: 1fr; }
}
@media (prefers-reduced-motion: reduce) {
    .lcs-choices button { transition: none; }
}

/* =========================================================================
   课时 0 专用：五度圈 SVG + 指板地图（书页 19–21 向导点练习）
   ========================================================================= */
.lcs-sechead h2 { margin: 0; font-size: 19px; font-weight: 700; line-height: 1.4; letter-spacing: -.02em; }
.lcs-cof { margin-top: 16px; display: flex; justify-content: center; }
.lcs-cof svg { width: min(420px, 100%); height: auto; }
.cof-maj { fill: var(--tint); stroke: var(--line); stroke-width: 1; }
.cof-min { fill: var(--card); stroke: var(--line); stroke-width: 1; }
.cof-maj.is-c, .cof-min.is-c { fill: var(--blue-soft); }
.cof-majname { font-size: 17px; font-weight: 700; fill: var(--ink); text-anchor: middle; dominant-baseline: middle; }
.cof-majname.is-c { fill: var(--blue); }
.cof-acc { font-size: 9.5px; fill: var(--ink-3); text-anchor: middle; dominant-baseline: middle; }
.cof-minname { font-size: 12px; font-weight: 600; fill: var(--ink-2); text-anchor: middle; dominant-baseline: middle; }
.cof-minname.is-c { fill: var(--blue); }
.cof-core { fill: var(--card); stroke: var(--line); }
.cof-coretitle { font-size: 16px; font-weight: 700; fill: var(--ink); text-anchor: middle; }
.cof-coresub { font-size: 9px; letter-spacing: .08em; fill: var(--ink-3); text-anchor: middle; }

.lcs-mapbar { display: flex; align-items: center; justify-content: space-between; gap: 12px; flex-wrap: wrap; margin-top: 16px; }
.lcs-mapstrings { display: inline-flex; gap: 5px; padding: 4px; border: 1px solid var(--line); border-radius: 12px; background: var(--tint); }
.lcs-mapstrings button {
    border: none; background: none; cursor: pointer; font: inherit;
    font-size: 12.5px; font-weight: 650; color: var(--ink-3);
    padding: 6px 12px; border-radius: 9px; transition: color .15s, background .15s;
}
.lcs-mapstrings button:hover { color: var(--ink); }
.lcs-mapstrings button.active { background: var(--card); color: var(--blue); box-shadow: var(--sh-1); }
.lcs-maproot { font-size: 13px; color: var(--ink-2); }
.lcs-maproot strong { color: #e03131; font-size: 17px; margin-right: 2px; }
.lcs-maproot span { color: var(--ink-3); }

.lcs-mapboard { margin-top: 12px; overflow-x: auto; border: 1px solid var(--line); border-radius: 14px; background: var(--card); padding: 14px 12px 10px; }
.lcs-maprow, .lcs-mapfrets { display: grid; grid-template-columns: 44px repeat(7, minmax(46px, 1fr)); align-items: center; }
.lcs-maprow { min-height: 46px; }
.lcs-maprow::before, .lcs-mapfrets::before { content: none; }
.lcs-maprow { position: relative; }
.lcs-maprow::after {
    content: ''; position: absolute; left: 44px; right: 0; top: 50%; height: 2px;
    background: var(--line-2); opacity: .55; pointer-events: none;
}
.lcs-maprow.is-root::after { background: #e03131; opacity: .3; }
.lcs-maplabel { font-size: 11.5px; font-weight: 650; color: var(--ink-3); text-align: center; position: relative; z-index: 1; }
.lcs-mapcell { display: flex; align-items: center; justify-content: center; min-height: 40px; position: relative; z-index: 1; }
.lcs-mapcell.is-rootfret { background: var(--tint); border-radius: 10px; }
.lcs-mapfrets { margin-top: 6px; }
.lcs-mapfrets .lcs-mapcell { min-height: 22px; font-size: 11px; color: var(--ink-3); font-variant-numeric: tabular-nums; }
.lcs-mapfrets .lcs-mapcell.is-rootfret { color: var(--blue); font-weight: 700; }

.lcs-dot {
    display: inline-flex; align-items: center; justify-content: center;
    min-width: 34px; height: 26px; padding: 0 6px; border-radius: 999px;
    font-size: 11px; font-weight: 700; color: #fff; letter-spacing: .01em;
    cursor: default; box-shadow: 0 1px 3px rgba(0, 0, 0, .18);
    font-style: normal; font-variant-numeric: tabular-nums;
}
.lcs-dot.g-root  { background: #e03131; min-width: 30px; }
.lcs-dot.g-chord { background: #1971c2; }
.lcs-dot.g-ext   { background: #f5b301; color: #5c4300; }
.lcs-dot.g-alt   { background: #9c36b5; }

.lcs-maplegend { display: flex; flex-wrap: wrap; gap: 8px 16px; margin-top: 12px; font-size: 12px; color: var(--ink-2); }
.lcs-maplegend .lg { display: inline-flex; align-items: center; gap: 6px; }
.lcs-maplegend .lg i {
    display: inline-flex; align-items: center; justify-content: center;
    min-width: 26px; height: 18px; padding: 0 5px; border-radius: 999px;
    font-size: 9.5px; font-weight: 700; color: #fff; font-style: normal;
}
.lcs-maplegend .g-root i  { background: #e03131; }
.lcs-maplegend .g-chord i { background: #1971c2; }
.lcs-maplegend .g-ext i   { background: #f5b301; color: #5c4300; }
.lcs-maplegend .g-alt i   { background: #9c36b5; }

[data-theme="dark"] .cof-maj { fill: rgba(255, 255, 255, .05); }
[data-theme="dark"] .cof-min { fill: transparent; }
[data-theme="dark"] .cof-maj.is-c, [data-theme="dark"] .cof-min.is-c { fill: rgba(41, 151, 255, .16); }
[data-theme="dark"] .cof-majname { fill: var(--ink); }
[data-theme="dark"] .cof-minname { fill: var(--ink-2); }
[data-theme="dark"] .cof-core { fill: rgba(255, 255, 255, .04); }
[data-theme="dark"] .lcs-mapboard { background: rgba(255, 255, 255, .03); }
[data-theme="dark"] .lcs-mapcell.is-rootfret { background: rgba(255, 255, 255, .07); }
[data-theme="dark"] .lcs-dot { box-shadow: 0 1px 4px rgba(0, 0, 0, .5); }

@media (max-width: 620px) {
    .lcs-mapstrings button { padding: 7px 10px; min-height: 38px; }
    .lcs-maprow, .lcs-mapfrets { grid-template-columns: 38px repeat(7, minmax(42px, 1fr)); }
    .lcs-maprow::after { left: 38px; }
    .lcs-dot { min-width: 30px; height: 24px; font-size: 10px; }
}

/* ---------- 课时 1 · 三和弦的指板可视化（教材指法图） ---------- */
/* 四类三和弦各收在一个大圆角框里，卡片本身不描边 */
.oc-arc {
    margin-top: 14px; padding: 20px 18px 18px;
    border: 1px solid var(--line); border-radius: 30px;
    background: var(--card); box-shadow: 0 8px 28px rgba(16, 32, 64, .05);
}
[data-theme="dark"] .oc-arc { background: rgba(255, 255, 255, .03); box-shadow: none; }

/* 教材四页通用版式：按根音弦分 4 行；左标签 + 右侧 shape 序列 */
.oc-maj { display: flex; flex-direction: column; gap: 16px; }
.oc-maj-row { display: grid; grid-template-columns: 82px minmax(0, 1fr); gap: 10px; align-items: center; }
.oc-maj-label {
    justify-self: start; padding: 5px 10px; border-radius: 999px;
    background: rgba(25, 113, 194, .09); color: var(--blue);
    font-size: 12px; font-weight: 750; white-space: nowrap;
}
.oc-maj-cards { display: flex; justify-content: center; flex-wrap: wrap; gap: 10px; }
.oc-maj-card { flex: 0 0 132px; width: 132px; }
.oc-maj-no { color: var(--ink-3); font-size: 12px; font-weight: 700; line-height: 1.2; }
.oc-maj-card .oc-card-svg svg { height: 140px; }
.oc-card {
    display: flex; flex-direction: column; align-items: center; gap: 6px;
    width: 100%; min-width: 0; padding: 0;
    border: 0; background: transparent; font-family: var(--font);
}
.oc-card-svg { display: block; width: 100%; }
.oc-card-svg svg { display: block; width: 100%; height: 150px; }

/* SVG 指板：线色跟随主题，手指号圆点与横按弧线统一蓝色 */
.oc-svg .oc-line { stroke: var(--line-2); stroke-width: 1.2; }
.oc-svg .oc-nut { stroke: var(--ink-2); stroke-width: 3; stroke-linecap: round; }
.oc-svg .oc-x { fill: var(--ink-3); font-weight: 700; }
.oc-svg .oc-dot { stroke: var(--card); stroke-width: 1.5; }
.oc-svg .oc-dot.f { fill: #1971c2; }
.oc-svg .oc-barre-arc { fill: none; stroke: #1971c2; stroke-width: 5.5; stroke-linecap: round; }
.oc-svg .oc-dt { fill: #fff; font-weight: 750; }

@media (max-width: 620px) {
    .oc-arc { padding: 15px 12px 14px; border-radius: 22px; }
    .oc-maj { gap: 18px; }
    .oc-maj-row { grid-template-columns: 1fr; gap: 6px; }
    .oc-maj-cards { justify-content: center; gap: 10px 8px; }
    .oc-maj-card { flex: 0 0 calc((100% - 8px) / 2); width: auto; }
    .oc-maj-card .oc-card-svg svg { max-width: 160px; margin: 0 auto; }
}

/* ---------- 课时 2 · 三和弦的转位：增/减三对称，不设转位 ---------- */
.iv-sym { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; margin-top: 14px; }
.iv-sym-card {
    display: flex; flex-direction: column; align-items: center; gap: 12px;
    padding: 18px 14px 16px; border: 1px solid var(--line); border-radius: 22px;
    background: var(--card); box-shadow: 0 8px 28px rgba(16, 32, 64, .05);
}
[data-theme="dark"] .iv-sym-card { background: rgba(255, 255, 255, .03); box-shadow: none; }
.iv-sym-top { display: flex; align-items: center; gap: 8px; }
.iv-sym-name { color: var(--ink); font-size: 15px; font-weight: 750; }
.iv-sym-badge {
    padding: 3px 9px; border-radius: 999px;
    background: rgba(224, 49, 49, .1); color: #e03131;
    font-size: 10.5px; font-weight: 700;
}
.iv-sym-seq { display: flex; align-items: center; justify-content: center; flex-wrap: wrap; gap: 4px; }
.iv-sym-seq b {
    display: inline-grid; place-items: center; min-width: 32px; height: 32px; padding: 0 7px;
    border-radius: 999px; background: var(--blue); color: #fff;
    font-size: 11px; font-weight: 750;
}
.iv-sym-seq em { padding: 0 3px; color: var(--ink-3); font-size: 10px; font-weight: 700; font-style: normal; }
.iv-sym-cap { color: var(--ink-3); font-size: 11.5px; font-weight: 600; }
.iv-sym-lead { margin: 12px 2px 0; color: var(--ink-2); font-size: 12.5px; line-height: 1.65; }

@media (max-width: 620px) {
    .iv-sym { gap: 9px; }
    .iv-sym-card { gap: 9px; padding: 14px 8px 13px; border-radius: 18px; }
    .iv-sym-name { font-size: 13px; }
    .iv-sym-seq { flex-wrap: nowrap; gap: 2px; white-space: nowrap; }
    .iv-sym-seq b {
        box-sizing: border-box; min-width: 26px; height: 26px; padding: 0 3px; font-size: 9.5px;
    }
    .iv-sym-seq em { padding: 0 1px; font-size: 9px; }
}