:root {
  color-scheme: light dark;
  --bg: #f5f6f8;
  --card: #ffffff;
  --sunken: #eceef2;
  --ink: #15171c;
  --muted: #5b6370;
  --line: #e1e4ea;
  --line-strong: #c5cad3;
  --accent: #4338ca;
  --accent-hover: #372fa8;
  --accent-ink: #ffffff;
  --accent-soft: #eceafc;
  --good: #167a45;
  --good-bg: #e5f4ec;
  --bad: #c2352b;
  --bad-bg: #fcebe9;
  /* 흰 악보 위에 얹는 색은 테마와 상관없이 같은 값을 쓴다. */
  --on-sheet-accent: #4338ca;
  --on-sheet-good: #167a45;
  --on-sheet-bad: #c2352b;
  --on-sheet-diff: #d9730d;
  --radius: 10px;
  --nav-h: 60px;
  font-family: "Pretendard", "Apple SD Gothic Neo", "Malgun Gothic", "Noto Sans KR", system-ui, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1115;
    --card: #181b21;
    --sunken: #21252d;
    --ink: #e9ebef;
    --muted: #9aa2af;
    --line: #2a2f38;
    --line-strong: #3a414d;
    --accent: #8f98ff;
    --accent-hover: #a9b0ff;
    --accent-ink: #0f1115;
    --accent-soft: #232748;
    --good: #5fd28f;
    --good-bg: #16291f;
    --bad: #ff8a80;
    --bad-bg: #321a18;
  }
}

* { box-sizing: border-box; }
/* display를 지정한 요소(.btn 등)에서도 hidden 속성이 먹도록 한다. */
[hidden] { display: none !important; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--ink); line-height: 1.55; font-size: 15px; -webkit-tap-highlight-color: transparent; }
a { color: var(--accent); }
h1 { font-size: 24px; line-height: 1.25; margin: 0 0 6px; letter-spacing: -.02em; }
h2 { font-size: 19px; margin: 0 0 4px; letter-spacing: -.01em; }
h3 { font-size: 15px; margin: 24px 0 8px; }
button { font: inherit; color: inherit; cursor: pointer; touch-action: manipulation; }
button:disabled { cursor: not-allowed; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* 머리말과 내비게이션 */
.top {
  position: sticky; top: 0; z-index: 20; display: flex; align-items: center; gap: 8px 16px;
  padding: 10px 24px; background: var(--bg); border-bottom: 1px solid var(--line);
}
.brand { font-weight: 800; font-size: 17px; color: var(--ink); text-decoration: none; letter-spacing: -.03em; }
.piece-btn {
  display: inline-flex; align-items: center; gap: 6px; min-width: 0; max-width: 300px; margin-left: auto;
  background: var(--card); border: 1px solid var(--line); border-radius: 99px; padding: 6px 12px; font-size: 14px;
}
.piece-btn:hover { border-color: var(--line-strong); }
.piece-btn span { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
#nav { display: flex; gap: 2px; order: -1; }
#nav button { display: inline-flex; align-items: center; gap: 6px; background: none; border: 0; padding: 7px 12px; border-radius: 8px; color: var(--muted); font-size: 14.5px; }
#nav button svg { width: 18px; height: 18px; fill: none; stroke: currentColor; stroke-width: 1.7; stroke-linecap: round; stroke-linejoin: round; }
#nav button:hover { color: var(--ink); }
#nav button.on { color: var(--accent); background: var(--accent-soft); font-weight: 700; }
.brand { order: -2; }

main { max-width: 1120px; margin: 0 auto; padding: 22px 24px 40px; min-height: 70vh; }
.foot { max-width: 1120px; margin: 0 auto; padding: 16px 24px 40px; font-size: 12.5px; color: var(--muted); border-top: 1px solid var(--line); }
.foot p { margin: 2px 0; }
.loading, .empty { padding: 56px 16px; text-align: center; color: var(--muted); }
.toast {
  position: fixed; left: 50%; bottom: 24px; transform: translateX(-50%); z-index: 60; max-width: calc(100vw - 32px);
  background: var(--ink); color: var(--bg); padding: 10px 16px; border-radius: 10px; font-size: 14px; box-shadow: 0 6px 20px rgb(0 0 0 / .2);
}
.drop-overlay { position: fixed; inset: 0; z-index: 70; display: grid; place-items: center; background: color-mix(in srgb, var(--accent) 22%, transparent); backdrop-filter: blur(3px); }
.drop-overlay div { background: var(--card); border: 2px dashed var(--accent); border-radius: 16px; padding: 36px 48px; font-size: 20px; font-weight: 700; }
.drop-overlay[hidden], .toast[hidden] { display: none; }

/* 버튼 */
.btn { display: inline-flex; align-items: center; justify-content: center; min-height: 40px; padding: 7px 14px; border-radius: 8px; border: 1px solid transparent; background: none; white-space: nowrap; }
.btn.big { min-height: 48px; padding: 10px 28px; font-size: 16px; }
.btn.primary { background: var(--accent); color: var(--accent-ink); font-weight: 700; }
.btn.primary:hover:not(:disabled) { background: var(--accent-hover); }
.btn.primary:disabled { background: var(--line-strong); color: var(--muted); }
.btn.ghost { border-color: var(--line-strong); background: var(--card); }
.btn.ghost:hover:not(:disabled) { border-color: var(--muted); }
.btn.ghost.on { border-color: var(--accent); color: var(--accent); }
.btn.ghost:disabled { color: var(--muted); opacity: .6; }
.btn.link { padding: 4px 2px; min-height: 0; color: var(--muted); }
.btn.link:hover { color: var(--ink); }
.btn.danger { border-color: var(--bad); color: var(--bad); background: none; }
.danger-text:hover { color: var(--bad); }
.quiz-actions.center { justify-content: center; margin-top: 12px; }

.segmented { display: inline-flex; border: 1px solid var(--line-strong); border-radius: 8px; overflow: hidden; background: var(--card); }
.segmented button { border: 0; background: none; padding: 5px 12px; min-height: 34px; font-size: 13.5px; white-space: nowrap; }
.segmented button + button { border-left: 1px solid var(--line); }
.segmented button.on { background: var(--ink); color: var(--bg); }

/* 메인 히어로와 활용 장면 */
.hero { padding: 28px 4px 8px; }
.hero h1 { font-size: clamp(28px, 6vw, 44px); line-height: 1.2; letter-spacing: -.03em; margin: 0 0 14px; }
.hero h1 em { font-style: normal; color: var(--accent); }
.hero-lead { margin: 0 0 22px; font-size: 17px; color: var(--muted); max-width: 40ch; }
.hero-cta { display: flex; flex-wrap: wrap; gap: 10px; }
.hero-sub { margin: 14px 0 0; font-size: 13.5px; color: var(--muted); }
.hero-chips { list-style: none; display: flex; flex-wrap: wrap; gap: 8px; padding: 0; margin: 18px 0 0; }
.hero-chips li { padding: 6px 14px; border-radius: 99px; font-size: 14px; font-weight: 600; background: var(--accent-soft); color: var(--accent); }
.hero-chips li:nth-child(2n) { background: var(--good-bg); color: var(--good); }
.hero-chips li:nth-child(3n) { background: var(--bad-bg); color: var(--bad); }
.hero .report { max-width: 560px; }
.showcase { margin: 36px auto 0; max-width: 1040px; }
.showcase-lead { margin: 0 0 14px; color: var(--muted); }
.demo-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 16px; align-items: start; grid-auto-flow: dense; }
@media (min-width: 900px) { .demo-card.wide { grid-column: span 2; } }
.demo-card { margin: 0; background: var(--card); border: 1px solid var(--line); border-radius: 14px; overflow: hidden; display: flex; flex-direction: column; }
.demo-frame { background: #fff; display: grid; place-items: center; }
.demo-frame img { display: block; width: 100%; height: auto; }
.demo-card figcaption { display: flex; flex-direction: column; gap: 2px; padding: 12px 16px 14px; }
.demo-card figcaption b { font-size: 16px; }
.demo-card figcaption span { color: var(--muted); font-size: 14px; }

/* 보관함 */
.library { max-width: 720px; margin: 0 auto; }
.library:has(.hero) { max-width: 1040px; }
.dropzone { text-align: center; background: var(--card); border: 2px dashed var(--line-strong); border-radius: 16px; padding: 36px 24px 28px; }
.dropzone p { margin: 0 auto 18px; color: var(--muted); max-width: 46ch; }
.dropzone .dz-sub { margin: 14px auto 0; font-size: 13px; }
.report { list-style: none; margin: 18px 0 0; padding: 0; text-align: left; display: flex; flex-direction: column; gap: 6px; }
.report li { display: flex; gap: 10px; align-items: baseline; font-size: 14px; padding: 8px 12px; border-radius: 8px; }
.report li b { flex: none; font-size: 12px; }
.report li.ok { background: var(--good-bg); color: var(--good); }
.report li.fail { background: var(--bad-bg); color: var(--bad); }
.lib-section { max-width: 720px; margin: 28px auto 0; }
.piece-cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 10px; margin-top: 10px; }
.piece-card { display: flex; flex-direction: column; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; }
.piece-card:hover { border-color: var(--line-strong); }
.pc-main { display: flex; flex-direction: column; gap: 3px; text-align: left; background: none; border: 0; padding: 14px 16px 10px; flex: 1; }
.pc-main b { font-size: 16px; }
.pc-main span:not(.bar) { color: var(--muted); font-size: 13.5px; }
.pc-main .bar { margin-top: 6px; }
.pc-tools { display: flex; gap: 14px; padding: 0 16px 10px; font-size: 13px; }

/* 연습 목록 */
.piece-head { margin-bottom: 14px; }
.piece-head p { margin: 0; color: var(--muted); }
.range-bar { margin-bottom: 14px; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 0 14px; font-size: 14px; }
.range-bar summary { display: flex; align-items: center; gap: 10px; min-height: 44px; cursor: pointer; list-style: none; }
.range-bar summary::-webkit-details-marker { display: none; }
.range-bar summary::after { content: '▾'; margin-left: auto; color: var(--muted); }
.range-bar[open] summary::after { content: '▴'; }
.range-label { font-weight: 700; }
.range-now { color: var(--accent); font-weight: 600; }
.range-body { padding-bottom: 12px; display: flex; flex-wrap: wrap; gap: 8px 14px; align-items: center; }
.range-inputs { display: flex; align-items: center; gap: 6px; }
.range-inputs input { width: 68px; font: inherit; padding: 6px 8px; border: 1px solid var(--line-strong); border-radius: 8px; background: var(--bg); color: var(--ink); }
.chips { display: flex; flex-wrap: wrap; gap: 6px; }
.chip { border: 1px solid var(--line-strong); background: none; border-radius: 99px; padding: 4px 12px; font-size: 13px; color: var(--muted); }
.chip:hover { color: var(--ink); border-color: var(--muted); }
.chip.on { background: var(--ink); color: var(--bg); border-color: var(--ink); }

.mix-card { width: 100%; display: flex; justify-content: space-between; align-items: center; gap: 16px; text-align: left; background: var(--accent); color: var(--accent-ink); border: 0; border-radius: var(--radius); padding: 18px 22px; }
.mix-card:hover { background: var(--accent-hover); }
.mix-card b { font-size: 18px; }
.mix-card p { margin: 2px 0 0; opacity: .88; font-size: 14px; }
.mix-go { font-weight: 700; white-space: nowrap; }
.mode-group { margin-top: 24px; }
.mode-group h2 { font-size: 13px; color: var(--muted); font-weight: 700; margin-bottom: 8px; }
.mode-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 8px; }
.mode-card { display: flex; flex-direction: column; gap: 2px; text-align: left; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 13px 15px; }
.mode-card:hover { border-color: var(--accent); }
.mode-card b { font-size: 15.5px; }
.mode-card span { color: var(--muted); font-size: 13.5px; }

/* 문제 화면 */
.mode-nav { margin-bottom: 6px; }
.quiz-head { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 8px 24px; align-items: flex-start; margin-bottom: 12px; }
.quiz-prompt { margin: 0; color: var(--muted); max-width: 68ch; }
.eyebrow { font-size: 12.5px; font-weight: 700; color: var(--accent); }
.quiz-body { display: flex; flex-direction: column; gap: 12px; }
.quiz-actions { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 14px; }
.feedback { min-height: 26px; margin-top: 12px; font-size: 14.5px; }
.feedback.good { color: var(--good); font-weight: 700; }
.feedback.bad { color: var(--bad); font-weight: 700; }

/* 악보 */
.sheet { position: relative; background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 6px; overflow: hidden; color: #000; }
.sheet svg { display: block; max-width: 100%; height: auto; margin: 0 auto; }
.sheet.wide svg { width: 100%; }
.no-numbers .mNum { display: none; }
.stem-sheet { max-width: 620px; }
.note.playing .notehead, .note.playing .notehead use { fill: var(--on-sheet-accent); color: var(--on-sheet-accent); }
.measure { cursor: default; }
.viewer-pages .measure { cursor: pointer; }
.viewer-pages .measure.current > .staff > path { stroke: var(--on-sheet-accent); stroke-opacity: .55; }
.note.blanked .notehead, .note.blanked .accid, .note.blanked .dots, .note.blanked .artic, .note.blanked > .stem,
.note.faded .notehead, .note.faded .accid, .note.faded .dots, .note.faded > .stem { visibility: hidden; }
/* 화음 칸을 가리면 화음 전체의 기둥·꼬리·붙은 기호도 숨긴다. 길이로 음높이가 드러나기 때문이다. */
.chord.blanked-chord > .stem, .chord.blanked-chord > .artic, .chord.blanked-chord > .dots { visibility: hidden; }
.mark-right .notehead, .mark-right .accid, .mark-right use { fill: var(--on-sheet-good); color: var(--on-sheet-good); }
.mark-wrong .notehead, .mark-wrong .accid, .mark-wrong use { fill: var(--on-sheet-bad); color: var(--on-sheet-bad); }
.mark-target .notehead, .mark-target use { fill: var(--on-sheet-bad); color: var(--on-sheet-bad); }
.mark-diff .notehead, .mark-diff .accid, .mark-diff use { fill: var(--on-sheet-diff); color: var(--on-sheet-diff); }
.q-mark, .q-mark * { fill: var(--on-sheet-bad); font-weight: 700; }
.fade-all .beam polygon, .fade-all .chord > .stem, .fade-all .slur, .fade-all .tie, .fade-all .tuplet, .fade-all .ledgerLines,
.fade-all .dynam, .fade-all .hairpin, .fade-all .artic, .fade-all .rest, .fade-all .dir, .fade-all .pedal, .fade-all .octave { visibility: hidden; }
.hand-hidden .note, .hand-hidden .chord, .hand-hidden .rest, .hand-hidden .beam, .hand-hidden .tuplet, .hand-hidden .ledgerLines { visibility: hidden; }
.hand-hiding .slur, .hand-hiding .tie { visibility: hidden; }

.blank-marker { position: absolute; transform: translateX(-50%); min-width: 26px; min-height: 22px; display: flex; align-items: center; justify-content: center; background: color-mix(in srgb, var(--on-sheet-bad) 14%, transparent); border: 1.5px dashed var(--on-sheet-bad); border-radius: 6px; pointer-events: none; }
.blank-marker span { color: var(--on-sheet-bad); font-weight: 800; font-size: 15px; background: #fff; border-radius: 4px; padding: 0 3px; }
.blank-marker.current { background: color-mix(in srgb, var(--on-sheet-bad) 28%, transparent); border-style: solid; }

/* 건반 */
/* 건반은 항상 실제 피아노 비율(흰 건반 폭:길이 ≈ 1:6.4, 검은 건반 폭 52%·길이 63%)로 그린다.
   높이는 aspect-ratio(--ar)가 정하므로 가로가 늘면 세로도 같은 비율로 늘고, 너무 커지지 않게 건반당 34px에서 멈춘다. */
.piano-scroll { overflow-x: auto; overscroll-behavior-x: contain; width: 100%; max-width: calc(var(--keys, 14) * 34px + 16px); margin: 0 auto; padding: 10px 8px 0; background: linear-gradient(#2c2f39, #1b1d24); border-radius: 12px; }
.piano { position: relative; width: 100%; min-width: calc(var(--keys, 14) * 24px); aspect-ratio: var(--ar, 2.2); user-select: none; touch-action: pan-x; }
.key { position: absolute; top: 0; border: 0; padding: 0; }
.key.white { height: 100%; z-index: 1; display: flex; align-items: flex-end; justify-content: center; border-radius: 0 0 5px 5px;
  background: linear-gradient(180deg, #fbfbfc 0%, #ffffff 70%, #e6e9ee 100%); box-shadow: inset -1px 0 0 #c3c8d1, inset 1px 0 0 #ffffff, inset 0 -3px 0 #d5d9e1; }
.key.white small { font-size: 10px; color: #6a7280; padding-bottom: 7px; pointer-events: none; }
.key.black { height: 63%; z-index: 2; border-radius: 0 0 3px 3px;
  background: linear-gradient(180deg, #3b3f4b 0%, #14161c 88%, #2a2d37 100%); box-shadow: inset 1px 0 0 rgb(255 255 255 / .12), 0 2px 3px rgb(0 0 0 / .45); }
.key.white:hover { background: linear-gradient(180deg, #f1f3f8 0%, #f7f8fb 70%, #dde1e9 100%); }
.key.black:hover { background: linear-gradient(180deg, #4a4f5d 0%, #1e2128 88%, #333743 100%); }
.key.white:active { box-shadow: inset -1px 0 0 #c3c8d1, inset 1px 0 0 #fff, inset 0 -1px 0 #d5d9e1; }
.key.white.picked, .key.white.picked:hover { background: #dcdcfb; box-shadow: inset 0 0 0 3px #4338ca; }
.key.black.picked, .key.black.picked:hover { background: #4338ca; }
.key.right, .key.right:hover { background: #2f9e62; }
.key.wrong, .key.wrong:hover { background: #d9534a; }
.key.answer, .key.answer:hover { background: #2f9e62; box-shadow: 0 0 0 2px #2f9e62; }

/* 객관식 */
.choices { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 8px; }
.choices.two { grid-template-columns: repeat(auto-fit, minmax(140px, 240px)); }
.choice { background: var(--card); border: 1.5px solid var(--line); border-radius: var(--radius); padding: 12px; font-size: 16px; font-weight: 600; min-height: 48px; }
.choice:hover:not(:disabled) { border-color: var(--accent); }
.choice.right, .sheet-choice.right { border-color: var(--good); background: var(--good-bg); color: var(--good); }
.choice.wrong, .sheet-choice.wrong { border-color: var(--bad); background: var(--bad-bg); color: var(--bad); }
.choice:disabled { cursor: default; }
.sheet-choices { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 8px; }
/* 한 마디짜리 보기는 항상 한 줄에 네 개. 좁은 화면에서는 아래 미디어 쿼리가 두 줄로 바꾼다. */
.sheet-choices.compact { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.sheet-choice { position: relative; padding: 6px; background: var(--card); border: 2px solid var(--line); border-radius: var(--radius); }
.sheet-choice:hover:not(:disabled) { border-color: var(--accent); }
.sheet-choice .sheet { border: 0; padding: 2px; }
.choice-num { position: absolute; top: 4px; left: 8px; font-size: 12px; font-weight: 700; color: #5b6370; z-index: 1; }

/* 순서 퍼즐 */
.slots.grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 10px; }
.slots.stack { display: flex; flex-direction: column; gap: 10px; }
.slot { position: relative; min-height: 112px; padding: 8px 8px 8px 30px; background: var(--sunken); border: 1.5px solid transparent; border-radius: var(--radius); display: flex; align-items: center; transition: background .12s, border-color .12s; }
.slot.over { border-color: var(--accent); background: var(--accent-soft); }
.slot.right { border-color: var(--good); background: var(--good-bg); }
.slot.wrong { border-color: var(--bad); background: var(--bad-bg); }
.slot.pinned { border-color: var(--accent); }
.slot-num { position: absolute; left: 10px; top: 8px; font-weight: 800; color: var(--muted); font-size: 13.5px; }
.piece { position: relative; width: 100%; cursor: grab; touch-action: none; border-radius: var(--radius); user-select: none; -webkit-user-select: none; -webkit-touch-callout: none; }
.piece svg { pointer-events: none; }
.piece:hover .sheet { border-color: var(--line-strong); }
.piece.selected .sheet { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent); }
.piece.pinned { cursor: default; }
.piece.dragging { opacity: .3; }
.piece.landed { animation: land .25s ease-out; }
@keyframes land { from { transform: scale(.96); } to { transform: none; } }
.piece.ghost { position: fixed; top: 0; left: 0; z-index: 40; pointer-events: none; box-shadow: 0 10px 28px rgb(0 0 0 / .3); opacity: .96; touch-action: none; }
.piece-tag { position: absolute; left: 8px; bottom: 8px; font-size: 12px; font-weight: 700; color: var(--on-sheet-accent); background: #fff; padding: 1px 6px; border-radius: 4px; }

.locate { position: relative; padding: 8px 4px 34px; }
.locate-value { display: block; font-size: 22px; font-weight: 800; text-align: center; }
.locate-slider { width: 100%; height: 36px; accent-color: var(--accent); }
.locate-marks { position: relative; height: 18px; margin-top: 4px; }
.locate-marks span { position: absolute; font-size: 11px; color: var(--muted); white-space: nowrap; border-left: 1px solid var(--line-strong); padding-left: 3px; max-width: 80px; overflow: hidden; text-overflow: ellipsis; }

/* 악보 보기 */
.viewer-bar { position: sticky; top: 61px; z-index: 10; display: flex; flex-wrap: wrap; gap: 8px 16px; align-items: center; padding: 10px 0; background: var(--bg); font-size: 13.5px; }
.viewer-where { font-weight: 700; min-width: 70px; }
.field { display: inline-flex; align-items: center; gap: 6px; color: var(--muted); white-space: nowrap; }
.field input[type=range] { width: 100px; accent-color: var(--accent); }
.check { display: inline-flex; gap: 4px; align-items: center; color: var(--muted); white-space: nowrap; }
.viewer-pages { position: relative; display: flex; flex-direction: column; gap: 10px; }
.page svg { width: 100%; }
.heat { position: absolute; pointer-events: none; border-radius: 3px; }

/* 진도와 비교 */
.stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(130px, 1fr)); gap: 8px; }
.stat { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 10px 14px; }
.stat b { display: block; font-size: 24px; letter-spacing: -.02em; }
.stat span { font-size: 12.5px; color: var(--muted); }
.heatmap { display: grid; grid-template-columns: repeat(auto-fill, minmax(40px, 1fr)); gap: 3px; }
.cell { border: 0; border-radius: 4px; height: 36px; font-size: 12px; padding: 0; color: var(--muted); }
.cell:hover { outline: 2px solid var(--ink); }
.section-bars { display: flex; flex-direction: column; gap: 4px; }
.section-bar { display: grid; grid-template-columns: minmax(150px, 280px) 1fr 44px; gap: 12px; align-items: center; text-align: left; background: none; border: 0; padding: 7px 4px; border-radius: 8px; }
.section-bar:hover { background: var(--sunken); }
.section-bar small { color: var(--muted); }
.bar { display: block; height: 8px; background: var(--line); border-radius: 4px; overflow: hidden; }
.bar i { display: block; height: 100%; background: var(--accent); }

.confusion-grid { display: grid; grid-template-columns: 230px 1fr; gap: 16px; align-items: start; }
.pair-list { display: flex; flex-direction: column; gap: 2px; max-height: 66vh; overflow: auto; }
.pair { display: grid; grid-template-columns: 74px 1fr 36px; gap: 6px; align-items: center; background: none; border: 0; padding: 7px 6px; border-radius: 8px; text-align: left; font-size: 13px; }
.pair:hover { background: var(--sunken); }
.pair.on { background: var(--ink); color: var(--bg); }
.pair.on .bar { background: var(--muted); }
.pair.on .bar i { background: var(--bg); }
.compare { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 12px; }
.compare-col { display: flex; flex-direction: column; gap: 6px; align-items: flex-start; min-width: 0; }
.compare-col h3 { margin: 0; }
.compare-col .sheet { width: 100%; }
.compare-actions { grid-column: 1 / -1; }

.mix-meter { height: 6px; background: var(--line); border-radius: 3px; overflow: hidden; margin-bottom: 16px; }
.mix-meter i { display: block; height: 100%; width: 0; background: var(--accent); transition: width .25s; }
.mix-done { padding: 32px 0; }

/* 모바일: 하단 탭, 큰 터치 영역, 가로 스크롤 */
@media (max-width: 720px) {
  body { font-size: 15.5px; padding-bottom: calc(var(--nav-h) + env(safe-area-inset-bottom)); }
  h1 { font-size: 21px; }
  .top { padding: 8px 14px; padding-top: calc(8px + env(safe-area-inset-top)); gap: 8px; }
  .brand { order: 0; font-size: 16px; }
  .piece-btn { order: 1; flex: 1; max-width: none; min-height: 40px; justify-content: space-between; margin-left: 0; }
  .add-btn { order: 2; padding: 7px 12px; min-height: 40px; }
  #nav {
    position: fixed; left: 0; right: 0; bottom: 0; z-index: 30; order: 3; gap: 0;
    height: calc(var(--nav-h) + env(safe-area-inset-bottom)); padding-bottom: env(safe-area-inset-bottom);
    background: var(--card); border-top: 1px solid var(--line);
  }
  #nav button { flex: 1; flex-direction: column; justify-content: center; gap: 2px; padding: 6px 0; border-radius: 0; font-size: 11.5px; min-height: var(--nav-h); }
  #nav button svg { width: 22px; height: 22px; }
  #nav button.on { background: none; }
  main { padding: 16px 14px 28px; }
  .foot { padding: 14px 14px 28px; }
  .toast { bottom: calc(var(--nav-h) + env(safe-area-inset-bottom) + 14px); }
  .btn { min-height: 44px; }
  .btn.link { min-height: 36px; }
  .segmented button { min-height: 38px; padding: 6px 12px; }
  .dropzone { padding: 28px 16px 22px; }
  .range-inputs input { font-size: 16px; width: 76px; }
  .chip { padding: 7px 12px; }
  .mix-card { padding: 16px; }
  .mode-list { grid-template-columns: 1fr; }
  .mode-card { padding: 14px 16px; min-height: 64px; }
  .piece-cards { grid-template-columns: 1fr; }
  .quiz-actions .btn { flex: 1 1 auto; }
  .choices { grid-template-columns: 1fr 1fr; }
  .choices.two { grid-template-columns: 1fr 1fr; }
  .sheet-choices, .compare { grid-template-columns: 1fr; }
  /* 한 마디짜리 조각·보기는 두 줄로 나란히 놓아 화면을 덜 차지하게 한다. */
  .slots.grid, .sheet-choices.compact { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 8px; }
  .slots.grid .slot { min-height: 0; padding: 24px 4px 4px; align-items: stretch; }
  .slots.grid .slot-num { top: 4px; left: 8px; }
  .slots.grid .piece-tag { font-size: 11px; }
  .sheet-choices.compact .sheet-choice { padding: 4px; }
  .sheet-choices.compact .sheet { padding: 2px; }
  .sheet { padding: 4px; overflow-x: auto; -webkit-overflow-scrolling: touch; }
  .sheet.wide svg { min-width: 520px; }
  .piece .sheet { overflow: hidden; }
  .piano-scroll { padding: 8px 4px 0; border-radius: 10px; }
  .piano { min-width: calc(var(--keys, 14) * 26px); }
  .key.white small { font-size: 9px; padding-bottom: 5px; }
  .locate-slider { height: 44px; }
  .viewer-bar { position: static; flex-wrap: nowrap; overflow-x: auto; padding: 8px 0; -webkit-overflow-scrolling: touch; }
  .viewer-bar > * { flex: none; }
  .confusion-grid { grid-template-columns: 1fr; }
  .pair-list { max-height: 190px; }
  .section-bar { grid-template-columns: 1fr 44px; }
  .section-bar > .bar { grid-column: 1 / -1; grid-row: 2; }
  .cell { height: 40px; }
  .stats { grid-template-columns: 1fr 1fr; }
}

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; }
}