:root {
  --bg: #f6f7f9; --card: #ffffff; --ink: #1c1f26; --muted: #5f6675; --line: #e3e6ec;
  --accent: #c8552e; --accent-ink: #fff; --accent-soft: #fbe9e1;
  --ok: #2e8b57; --ok-soft: #e3f3e9; --bad: #c0392b; --bad-soft: #fbe5e3; --warn: #b7791f; --warn-soft: #fbf0d9;
  --info: #2b6cb0; --info-soft: #e4eefa; --ja: #4a3f9a; --ja-soft: #ece9fb;
  --radius: 14px; --shadow: 0 1px 2px rgba(20,24,40,.06), 0 4px 16px rgba(20,24,40,.05);
  --nav-h: 60px; --font: -apple-system, BlinkMacSystemFont, "Hiragino Sans", "Noto Sans JP", "Segoe UI", Roboto, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root { --bg: #14161b; --card: #1d2027; --ink: #e8eaf0; --muted: #9aa2b1; --line: #2c313b; --accent: #e8734a; --accent-soft: #3a261e;
    --ok-soft: #1f3a2b; --bad-soft: #3d2320; --warn-soft: #3a3020; --info-soft: #1e2d42; --ja-soft: #2a2647; --shadow: none; }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; font-family: var(--font); background: var(--bg); color: var(--ink); line-height: 1.55; font-size: 16px; padding-bottom: calc(var(--nav-h) + env(safe-area-inset-bottom)); }
a { color: var(--info); }
button { font: inherit; }
main { max-width: 860px; margin: 0 auto; padding: 14px 14px 40px; }
h1 { font-size: 1.35rem; margin: 6px 0 12px; }
h2 { font-size: 1.1rem; margin: 18px 0 8px; }
h3 { font-size: 1rem; margin: 14px 0 6px; }
.muted { color: var(--muted); }
.small { font-size: .85rem; }
.row { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.grow { flex: 1; }
.card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 14px; box-shadow: var(--shadow); margin-bottom: 12px; }
.card.tight { padding: 10px 12px; }
.grid2 { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 10px; }
.chip { display: inline-block; padding: 2px 9px; border-radius: 999px; font-size: .78rem; background: var(--line); color: var(--ink); white-space: nowrap; }
.chip.accent { background: var(--accent-soft); color: var(--accent); }
.chip.ok { background: var(--ok-soft); color: var(--ok); }
.chip.bad { background: var(--bad-soft); color: var(--bad); }
.chip.warn { background: var(--warn-soft); color: var(--warn); }
.chip.info { background: var(--info-soft); color: var(--info); }
.chip.ja { background: var(--ja-soft); color: var(--ja); }
.btn { border: 1px solid var(--line); background: var(--card); color: var(--ink); border-radius: 12px; padding: 10px 14px; cursor: pointer; font-size: .95rem; touch-action: manipulation; }
.btn:active { transform: translateY(1px); }
.btn.primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.btn.ok { background: var(--ok); color: #fff; border-color: var(--ok); }
.btn.ghost { background: transparent; }
.btn.sm { padding: 6px 10px; font-size: .85rem; border-radius: 10px; }
.btn.block { display: block; width: 100%; text-align: center; }
.btn:disabled { opacity: .5; cursor: default; }
.seg { display: inline-flex; border: 1px solid var(--line); border-radius: 10px; overflow: hidden; }
.seg button { border: 0; background: transparent; color: var(--muted); padding: 6px 12px; cursor: pointer; }
.seg button.on { background: var(--accent); color: #fff; }
.bar { height: 8px; background: var(--line); border-radius: 999px; overflow: hidden; }
.bar > i { display: block; height: 100%; background: var(--accent); border-radius: 999px; transition: width .3s; }
.bar.ok > i { background: var(--ok); }
.bar.info > i { background: var(--info); }
.kpi { text-align: center; padding: 10px 6px; }
.kpi b { display: block; font-size: 1.5rem; line-height: 1.1; }
.kpi span { font-size: .78rem; color: var(--muted); }
.ring { width: 96px; height: 96px; }
.list { list-style: none; margin: 0; padding: 0; }
.list li { padding: 10px 0; border-top: 1px solid var(--line); }
.list li:first-child { border-top: 0; }
.tap { cursor: pointer; }
.tap:active { background: var(--accent-soft); }
input[type=text], input[type=password], select, textarea { font: inherit; padding: 10px 12px; border: 1px solid var(--line); border-radius: 10px; background: var(--card); color: var(--ink); width: 100%; }
label.check { display: flex; gap: 10px; align-items: flex-start; }
label.check input { width: 20px; height: 20px; margin-top: 3px; flex: none; }

/* bottom nav */
nav.tabs { position: fixed; left: 0; right: 0; bottom: 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); display: flex; z-index: 20; }
nav.tabs a { flex: 1; display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 2px; text-decoration: none; color: var(--muted); font-size: .68rem; }
nav.tabs a .ico { font-size: 1.25rem; line-height: 1; }
nav.tabs a.on { color: var(--accent); }
nav.tabs a .badge { position: absolute; margin-left: 26px; margin-top: -8px; background: var(--bad); color: #fff; border-radius: 999px; font-size: .62rem; padding: 0 5px; }
header.top { position: sticky; top: 0; z-index: 15; background: color-mix(in srgb, var(--bg) 88%, transparent); backdrop-filter: blur(10px); border-bottom: 1px solid var(--line); }
header.top .in { max-width: 860px; margin: 0 auto; padding: 8px 14px; display: flex; align-items: center; gap: 10px; }
header.top .title { font-weight: 700; }
#sync { font-size: .72rem; color: var(--muted); }
#sync.pending { color: var(--warn); }
#sync.err { color: var(--bad); }

/* bilingual text */
.bi { position: relative; -webkit-user-select: none; user-select: none; -webkit-touch-callout: none; }
.bi .en { display: block; }
.bi .ja { display: block; color: var(--ja); font-size: .93em; margin-top: 4px; padding-left: 8px; border-left: 3px solid var(--ja-soft); }
.lang-en .bi .ja { display: none; }
.lang-ja .bi .en { display: none; }
.lang-ja .bi .ja { padding-left: 0; border: 0; color: var(--ink); font-size: 1em; margin-top: 0; }
.bi.flip .ja { display: block !important; }
.lang-en .bi.flip .en, .lang-both .bi.flip .en { display: block; }
.lang-ja .bi.flip .en { display: block; color: var(--muted); font-size: .9em; margin-top: 4px; }
mark.kw { background: transparent; color: inherit; border-bottom: 2px dotted var(--accent); cursor: pointer; padding: 0 1px; }
.gloss { position: fixed; z-index: 50; background: var(--ink); color: var(--bg); padding: 8px 12px; border-radius: 10px; font-size: .9rem; max-width: 80vw; box-shadow: 0 6px 24px rgba(0,0,0,.25); }
.hint { font-size: .8rem; color: var(--muted); }

/* quiz */
.q-meta { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 8px; }
.stem { font-size: 1.02rem; margin-bottom: 12px; user-select: none; -webkit-user-select: none; -webkit-touch-callout: none; }
.opt { display: flex; gap: 10px; align-items: flex-start; border: 1.5px solid var(--line); border-radius: 12px; padding: 10px 12px; margin-bottom: 8px; cursor: pointer; background: var(--card); user-select: none; -webkit-user-select: none; -webkit-touch-callout: none; }
.opt .key { flex: none; width: 26px; height: 26px; border-radius: 50%; border: 1.5px solid var(--line); display: grid; place-items: center; font-weight: 600; font-size: .85rem; }
.opt.sel { border-color: var(--accent); background: var(--accent-soft); }
.opt.sel .key { background: var(--accent); color: #fff; border-color: var(--accent); }
.opt.correct { border-color: var(--ok); background: var(--ok-soft); }
.opt.correct .key { background: var(--ok); color: #fff; border-color: var(--ok); }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.opt.wrong .key { background: var(--bad); color: #fff; border-color: var(--bad); }
.opt .why { margin-top: 6px; font-size: .88rem; color: var(--muted); }
.feedback { border-radius: 12px; padding: 12px; margin: 10px 0; }
.feedback.ok { background: var(--ok-soft); } .feedback.bad { background: var(--bad-soft); }
.elim { background: var(--warn-soft); border-radius: 12px; padding: 10px 12px; font-size: .92rem; }
.err-btns { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; margin-top: 8px; }
.timer { font-variant-numeric: tabular-nums; font-weight: 700; }
.timer.low { color: var(--bad); }
.navgrid { display: grid; grid-template-columns: repeat(auto-fill, minmax(38px, 1fr)); gap: 6px; }
.navgrid button { padding: 6px 0; border-radius: 8px; border: 1px solid var(--line); background: var(--card); color: var(--ink); }
.navgrid button.answered { background: var(--info-soft); border-color: var(--info); }
.navgrid button.flag { border-color: var(--warn); background: var(--warn-soft); }
.navgrid button.cur { outline: 2px solid var(--accent); }
.sticky-bottom { position: sticky; bottom: calc(var(--nav-h) + 8px); background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 8px; display: flex; gap: 8px; z-index: 5; box-shadow: var(--shadow); }

/* lessons */
.lesson section { margin-bottom: 18px; }
.lesson .body p { margin: 6px 0; }
.lesson pre { background: #0f1218; color: #e6e9f0; padding: 10px 12px; border-radius: 10px; overflow-x: auto; font-family: var(--mono); font-size: .82rem; }
.lesson code { font-family: var(--mono); font-size: .88em; background: var(--line); padding: 1px 5px; border-radius: 5px; }
.lesson pre code { background: transparent; padding: 0; }
.lesson table { border-collapse: collapse; width: 100%; font-size: .9rem; margin: 6px 0; display: block; overflow-x: auto; }
.lesson td { border: 1px solid var(--line); padding: 4px 8px; }
.terms td { padding: 6px 8px; vertical-align: top; }
.terms td:first-child { font-weight: 600; white-space: nowrap; }

/* flashcards */
.flash { min-height: 220px; display: flex; flex-direction: column; justify-content: center; text-align: center; cursor: pointer; }
.flash .term { font-size: 1.6rem; font-weight: 700; }
.flash .ex { color: var(--muted); font-size: .95rem; margin-top: 10px; }
.flash .back { border-top: 1px dashed var(--line); margin-top: 12px; padding-top: 12px; }
.grade { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; }

/* charts */
.chart { width: 100%; height: auto; }
.chart text { font-size: 10px; fill: var(--muted); }
.tag-row { display: grid; grid-template-columns: 1fr auto; gap: 8px; align-items: center; padding: 6px 0; border-top: 1px solid var(--line); }

#toast { position: fixed; left: 50%; bottom: calc(var(--nav-h) + 20px); transform: translate(-50%, 20px); background: var(--ink); color: var(--bg); padding: 10px 16px; border-radius: 12px; opacity: 0; transition: .25s; z-index: 60; pointer-events: none; max-width: 90vw; }
#toast.show { opacity: 1; transform: translate(-50%, 0); }
.modal-bg { position: fixed; inset: 0; background: rgba(0,0,0,.45); display: grid; place-items: center; z-index: 40; padding: 16px; }
.modal { background: var(--card); border-radius: 16px; padding: 18px; width: min(460px, 100%); max-height: 90vh; overflow: auto; }
.week { border-left: 4px solid var(--line); padding-left: 10px; }
.week.cur { border-left-color: var(--accent); }
.week.past { opacity: .8; }
details summary { cursor: pointer; }
.empty { text-align: center; color: var(--muted); padding: 24px 8px; }
@media (min-width: 720px) { body { font-size: 16.5px; } .err-btns { grid-template-columns: repeat(4, 1fr); } }