:root {
  --bg: #ffffff;
  --side: #f6f6f3;
  --panel: #ffffff;
  --text: #1d1d1b;
  --muted: #6b6b66;
  --faint: #9a9a93;
  --line: #e6e5df;
  --hover: #ecebe5;
  --accent: #1f6f4a;
  --accent-ink: #ffffff;
  --accent-soft: #e5f1ea;
  --user-bubble: #f0efea;
  --mark: #fff1b8;
  --ball: #8a4b22;
  --code: #f4f3ee;
  --danger: #b3261e;
  --shadow: 0 1px 2px rgba(0,0,0,.05), 0 8px 24px rgba(0,0,0,.06);
  --radius: 14px;
  --font: ui-sans-serif, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --read: Charter, "Iowan Old Style", "Palatino Linotype", Georgia, serif;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #1b1c1a; --side: #141513; --panel: #222321; --text: #ecebe6; --muted: #a3a29b; --faint: #7a7973;
    --line: #2f302d; --hover: #2a2b28; --accent: #4fb985; --accent-ink: #0d1a13; --accent-soft: #1f3529;
    --user-bubble: #2a2b28; --mark: #5a4a12; --ball: #c27a47; --code: #262724; --danger: #f2827a;
    --shadow: 0 1px 2px rgba(0,0,0,.3), 0 8px 24px rgba(0,0,0,.3);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #1b1c1a; --side: #141513; --panel: #222321; --text: #ecebe6; --muted: #a3a29b; --faint: #7a7973;
  --line: #2f302d; --hover: #2a2b28; --accent: #4fb985; --accent-ink: #0d1a13; --accent-soft: #1f3529;
  --user-bubble: #2a2b28; --mark: #5a4a12; --ball: #c27a47; --code: #262724; --danger: #f2827a;
  --shadow: 0 1px 2px rgba(0,0,0,.3), 0 8px 24px rgba(0,0,0,.3);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; }
body { background: var(--bg); color: var(--text); font: 15px/1.55 var(--font); -webkit-font-smoothing: antialiased; }
button, input, select, textarea { font: inherit; color: inherit; }
button { cursor: pointer; }
.hidden { display: none !important; }
svg { width: 18px; height: 18px; flex: none; }

#app { display: flex; height: 100vh; height: 100dvh; overflow: hidden; }

/* ---------- sidebar ---------- */
#sidebar { width: 280px; flex: none; background: var(--side); border-right: 1px solid var(--line); display: flex; flex-direction: column; min-height: 0; }
.side-top { display: flex; align-items: center; justify-content: space-between; padding: 14px 14px 6px; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 650; font-size: 16px; letter-spacing: -.01em; }
.brand svg { width: 26px; height: 26px; }
.side-panel { flex: 1; min-height: 0; display: flex; flex-direction: column; padding: 0 8px; }
.new-chat { display: flex; align-items: center; gap: 8px; margin: 2px 4px 10px; padding: 9px 12px; border: 1px solid var(--line); background: var(--panel); border-radius: 10px; font-weight: 550; }
.new-chat:hover { background: var(--hover); }
.list-label { font-size: 12px; color: var(--faint); padding: 6px 10px 4px; text-transform: uppercase; letter-spacing: .05em; }
.chat-list { list-style: none; margin: 0; padding: 0; overflow-y: auto; flex: 1; }
.chat-list li { display: flex; align-items: center; border-radius: 8px; }
.chat-list li a { flex: 1; min-width: 0; padding: 8px 10px; color: var(--text); text-decoration: none; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; font-size: 14px; }
.chat-list li:hover, .chat-list li.active { background: var(--hover); }
.chat-list li .del { opacity: 0; border: 0; background: none; color: var(--faint); padding: 4px 8px; font-size: 16px; }
.chat-list li:hover .del { opacity: 1; }
.chat-list .empty { color: var(--faint); font-size: 13px; padding: 6px 10px; }


.side-bottom { display: flex; align-items: center; justify-content: space-between; gap: 8px; padding: 10px 12px; border-top: 1px solid var(--line); }
.index-status { display: flex; align-items: center; gap: 8px; font-size: 12.5px; color: var(--muted); min-width: 0; }
.index-status .txt { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.dot { width: 8px; height: 8px; border-radius: 50%; background: var(--faint); flex: none; }
.index-status.ready .dot { background: var(--accent); }
.index-status.busy .dot { background: #d79b2b; animation: pulse 1.2s infinite; }
.index-status.err .dot { background: var(--danger); }
@keyframes pulse { 50% { opacity: .35; } }
.icon-btn { border: 0; background: none; padding: 6px; border-radius: 8px; color: var(--muted); display: inline-flex; font-size: 22px; line-height: 1; }
.icon-btn:hover { background: var(--hover); color: var(--text); }

/* ---------- main ---------- */
#main { flex: 1; min-width: 0; display: flex; flex-direction: column; position: relative; }
.view { flex: 1; min-height: 0; display: flex; flex-direction: column; }
.topbar { display: none; }

/* chat */
.messages { flex: 1; overflow-y: auto; padding: 28px 16px 12px; }
.msg { max-width: 780px; margin: 0 auto 22px; }
.msg.user { display: flex; justify-content: flex-end; }
.msg.user .bubble { background: var(--user-bubble); padding: 10px 15px; border-radius: 18px; max-width: 85%; white-space: pre-wrap; overflow-wrap: anywhere; }
.msg.assistant .body { overflow-wrap: anywhere; }
.body > :first-child { margin-top: 0; }
.body p, .body ul, .body ol { margin: 0 0 .8em; }
.body ul, .body ol { padding-left: 1.4em; }
.body li { margin: .25em 0; }
.body em { font-style: italic; text-decoration: underline; text-decoration-thickness: .06em; text-underline-offset: .16em; }
.body h1, .body h2, .body h3 { font-size: 1.05em; margin: 1.2em 0 .4em; }
.body code { background: var(--code); padding: 1px 5px; border-radius: 5px; font-size: .92em; }
.body pre { background: var(--code); padding: 12px; border-radius: 10px; overflow-x: auto; }
.body table { border-collapse: collapse; margin: .6em 0 1em; display: block; overflow-x: auto; }
.body th, .body td { border: 1px solid var(--line); padding: 6px 10px; text-align: left; }
.body blockquote { margin: .6em 0; padding: .1em 1em; border-left: 3px solid var(--line); color: var(--muted); }
.cite { display: inline-flex; align-items: center; justify-content: center; min-width: 19px; height: 19px; padding: 0 5px; margin: 0 1px; border-radius: 6px; background: var(--accent-soft); color: var(--accent); font-size: 11.5px; font-weight: 650; text-decoration: none; vertical-align: 2px; cursor: pointer; font-family: var(--font); }
.cite:hover { background: var(--accent); color: var(--accent-ink); }
.cite-sep { color: var(--faint); font-size: 11px; margin: 0 1px; }
.status-line { color: var(--muted); font-size: 14px; display: flex; align-items: center; gap: 8px; }
.spinner { width: 14px; height: 14px; border: 2px solid var(--line); border-top-color: var(--accent); border-radius: 50%; animation: spin .8s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }
.plan { margin: 10px 0 0; padding-left: 22px; color: var(--faint); font-size: 13px; }
.plan li { margin: 2px 0; }
.searches { margin-top: 10px; font-size: 12.5px; color: var(--muted); line-height: 1.5; }
.searches b { color: var(--text); font-weight: 600; }
.err-box { border: 1px solid color-mix(in srgb, var(--danger) 40%, transparent); color: var(--danger); background: color-mix(in srgb, var(--danger) 8%, transparent); padding: 10px 14px; border-radius: 10px; font-size: 14px; }

.sources { margin-top: 14px; }
.sources summary { cursor: pointer; color: var(--muted); font-size: 13px; list-style: none; display: inline-flex; align-items: center; gap: 6px; user-select: none; }
.sources summary::-webkit-details-marker { display: none; }
.sources summary::before { content: "\25B8"; font-size: 11px; transition: transform .15s; }
.sources[open] summary::before { transform: rotate(90deg); }
.src-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 8px; margin-top: 10px; }
.src { text-align: left; border: 1px solid var(--line); background: var(--panel); border-radius: 10px; padding: 9px 11px; font-size: 13px; line-height: 1.35; }
.src:hover { border-color: var(--accent); }
.src .n { color: var(--accent); font-weight: 700; margin-right: 4px; }
.src .t { font-weight: 600; }
.src .s { color: var(--faint); display: block; margin-top: 3px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.src { cursor: pointer; }
.src .x { display: none; margin-top: 6px; color: var(--muted); font-size: 12.5px; line-height: 1.45; }
.src.open .x { display: block; }
.src.open .s { white-space: normal; }
.src.flash { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.meta-line { color: var(--faint); font-size: 12px; margin-top: 8px; }
.composer-left { display: flex; align-items: center; gap: 8px; min-width: 0; flex-wrap: wrap; }
.data-list { display: flex; flex-direction: column; gap: 8px; margin-top: 10px; }
.data-card { border: 1px solid var(--line); background: var(--panel); border-radius: 10px; font-size: 13px; }
.data-card > summary { cursor: pointer; list-style: none; padding: 9px 11px; display: flex; gap: 6px; align-items: baseline; min-width: 0; }
.data-card > summary::-webkit-details-marker { display: none; }
.data-card .n { color: var(--accent); font-weight: 700; flex: none; }
.data-card .t { font-family: ui-monospace, Consolas, monospace; font-size: 12px; color: var(--muted); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; min-width: 0; }
.data-card.err .t { color: var(--danger); }
.data-card.flash { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.data-body { padding: 0 11px 10px; max-height: 420px; overflow: auto; font-size: 12.5px; line-height: 1.45; }
.data-body table { border-collapse: collapse; font-size: 12px; }
.data-body th, .data-body td { border: 1px solid var(--line); padding: 3px 7px; text-align: left; white-space: nowrap; }
.data-body th { background: var(--code); font-weight: 600; }
.data-body p, .data-body ul { margin: 6px 0; }


.welcome { max-width: 680px; margin: 9vh auto 0; text-align: center; padding: 0 8px; }
.welcome h1 { font-size: 28px; letter-spacing: -.02em; margin: 0 0 6px; font-weight: 650; }
.welcome p { color: var(--muted); margin: 0 0 26px; }
.suggest { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; text-align: left; }
.suggest button { border: 1px solid var(--line); background: var(--panel); border-radius: 12px; padding: 12px 14px; font-size: 14px; line-height: 1.35; }
.suggest button:hover { background: var(--hover); }
.suggest small { display: block; color: var(--faint); margin-top: 3px; font-size: 12px; }

.composer-wrap { padding: 8px 16px 14px; }
.composer { max-width: 780px; margin: 0 auto; border: 1px solid var(--line); background: var(--panel); border-radius: 22px; padding: 10px 10px 8px 16px; box-shadow: var(--shadow); }
.composer:focus-within { border-color: color-mix(in srgb, var(--accent) 50%, var(--line)); }
.composer textarea { width: 100%; border: 0; outline: none; resize: none; background: transparent; max-height: 220px; padding: 4px 0; line-height: 1.5; }
.composer-row { display: flex; align-items: center; justify-content: space-between; gap: 8px; margin-top: 4px; }
.composer select { border: 1px solid var(--line); background: var(--bg); border-radius: 999px; padding: 4px 10px; font-size: 13px; color: var(--muted); max-width: 60%; }
/* lesson mode: progress + next-part button */
.lesson-bar { display: flex; align-items: center; gap: 10px; margin-top: 12px; font-size: 13px; color: var(--muted); }
.lesson-progress { font-weight: 600; color: var(--text); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.lesson-track { display: inline-flex; gap: 4px; flex: none; }
.lesson-track i { width: 18px; height: 5px; border-radius: 3px; background: var(--line); }
.lesson-track i.done { background: var(--accent); }
.next-btn { margin-top: 8px; border: 1px solid var(--accent); background: var(--accent-soft); color: var(--text); border-radius: 10px; padding: 9px 14px; font-weight: 600; font-size: 14px; }
.next-btn:hover { background: var(--accent); color: var(--accent-ink); }
.send { width: 34px; height: 34px; border-radius: 50%; border: 0; background: var(--accent); color: var(--accent-ink); display: inline-flex; align-items: center; justify-content: center; }
.send:disabled { opacity: .35; cursor: default; }
.send.stop { background: var(--text); color: var(--bg); }
.fine { max-width: 780px; margin: 7px auto 0; text-align: center; color: var(--faint); font-size: 12px; }


.btn { border: 1px solid var(--line); background: var(--panel); border-radius: 9px; padding: 7px 13px; font-weight: 550; font-size: 14px; }
.btn:hover { background: var(--hover); }
.btn.primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.btn.ghost { background: transparent; }

/* settings */
dialog { border: 1px solid var(--line); border-radius: 16px; padding: 0; background: var(--panel); color: var(--text); width: min(480px, calc(100vw - 32px)); box-shadow: var(--shadow); }
dialog::backdrop { background: rgba(0,0,0,.35); }
.settings-form { padding: 20px 22px; display: flex; flex-direction: column; gap: 14px; }
.settings-form h2 { margin: 0; font-size: 18px; }
.settings-form label { display: flex; flex-direction: column; gap: 6px; font-weight: 550; font-size: 14px; }
.settings-form input, .settings-form select { border: 1px solid var(--line); border-radius: 9px; padding: 8px 10px; background: var(--bg); font-weight: 400; }
.hint { color: var(--faint); font-size: 12.5px; font-weight: 400; }
.settings-row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.settings-row.end { justify-content: flex-end; margin-top: 4px; }
.side-actions { display: flex; align-items: center; gap: 2px; }

/* library catalog */
dialog.library { width: min(960px, calc(100vw - 28px)); max-height: 88vh; }
dialog.library[open] { display: flex; flex-direction: column; }
.library-head { display: flex; align-items: flex-start; justify-content: space-between; gap: 14px; padding: 20px 22px 12px; border-bottom: 1px solid var(--line); }
.library-head h2 { margin: 0 0 4px; font-size: 20px; }
.library-head p { margin: 0; }
.library-controls { display: flex; gap: 10px; flex-wrap: wrap; padding: 12px 22px; border-bottom: 1px solid var(--line); }
.library-controls input, .library-controls select { border: 1px solid var(--line); border-radius: 9px; padding: 8px 10px; background: var(--bg); }
.library-controls input { flex: 1; min-width: 220px; }
.lib-list { flex: 1; min-height: 0; overflow-y: auto; padding: 4px 22px 22px; }
.lib-shelf { margin: 18px 0 8px; font-size: 12px; color: var(--faint); text-transform: uppercase; letter-spacing: .05em; }
.lib-books { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 10px; }
.lib-book { border: 1px solid var(--line); border-radius: 10px; padding: 12px 14px; background: var(--panel); }
.lib-book h3 { margin: 0 0 2px; font-size: 15px; line-height: 1.35; }
.lib-book .by { color: var(--muted); font-size: 13px; }
.lib-book .meta { color: var(--faint); font-size: 12px; margin-top: 6px; }
.lib-book .overview { color: var(--muted); font-size: 13px; margin-top: 8px; display: -webkit-box; -webkit-line-clamp: 4; -webkit-box-orient: vertical; overflow: hidden; }

.only-mobile { display: none !important; }
.scrim { display: none; }

@media (max-width: 760px) {
  .only-mobile { display: inline-flex !important; }
  #sidebar { position: fixed; inset: 0 auto 0 0; z-index: 30; transform: translateX(-100%); transition: transform .2s; width: 290px; max-width: 86vw; }
  #sidebar.open { transform: none; }
  .scrim { display: block; position: fixed; inset: 0; background: rgba(0,0,0,.35); z-index: 20; }
  .topbar { display: flex !important; align-items: center; gap: 8px; padding: 8px 10px; border-bottom: 1px solid var(--line); font-weight: 600; }
  .messages { padding: 18px 16px 8px; }
  .suggest { grid-template-columns: 1fr; }
  .welcome { margin-top: 5vh; }
}