:root {
  --bg: #f6f7f9;
  --panel: #ffffff;
  --border: #e3e6ea;
  --text: #1f2328;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-text: #ffffff;
  --user: #e8efff;
  --tool: #f3f4f6;
  --error: #b42318;
  --ok: #047857;
  --warn: #b45309;
  font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1419; --panel: #161b22; --border: #2d333b; --text: #e6edf3; --muted: #9aa4af;
    --accent: #3b82f6; --user: #1e2a44; --tool: #1f242b; --error: #f87171; --ok: #34d399; --warn: #fbbf24;
  }
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text); height: 100vh; }
.hidden { display: none !important; }
.muted { color: var(--muted); }
.small { font-size: 12px; }
.error { color: var(--error); min-height: 1.2em; }
button { cursor: pointer; border: 1px solid var(--border); background: var(--panel); color: var(--text); border-radius: 6px; padding: 6px 12px; font: inherit; }
button.small { padding: 2px 8px; font-size: 12px; margin-left: 8px; }
button.link { border: none; background: none; color: var(--accent); padding: 0; }
button[type="submit"] { background: var(--accent); color: var(--accent-text); border-color: var(--accent); }

.login { display: flex; align-items: center; justify-content: center; height: 100vh; }
.login-card { background: var(--panel); border: 1px solid var(--border); border-radius: 12px; padding: 32px; width: min(380px, 90vw); display: flex; flex-direction: column; gap: 12px; }
.login-card h1 { margin: 0; font-size: 22px; }
.login-card label { display: flex; flex-direction: column; gap: 4px; font-size: 14px; }
.login-card input, .login-card select { padding: 8px; border: 1px solid var(--border); border-radius: 6px; background: var(--bg); color: var(--text); font: inherit; }

.app { display: grid; grid-template-columns: 300px minmax(0, 1fr); height: 100vh; --viewer-w: 520px; }
.app.with-viewer { grid-template-columns: 300px minmax(0, 1fr) var(--viewer-w); }
.sidebar { background: var(--panel); border-right: 1px solid var(--border); display: flex; flex-direction: column; overflow: hidden; min-width: 0; min-height: 0; }
.sidebar-head { flex: none; padding: 14px 10px 8px; border-bottom: 1px solid var(--border); }
.sidebar-body { flex: 1; min-height: 0; overflow-y: auto; overflow-x: hidden; padding: 12px 16px 16px; display: flex; flex-direction: column; gap: 18px; }
.sidebar-foot { flex: none; padding: 8px 10px 10px; border-top: 1px solid var(--border); display: flex; flex-direction: column; gap: 8px; }
.sidebar-foot .account { display: flex; justify-content: space-between; align-items: center; gap: 8px; padding: 4px 6px; font-size: 13px; min-width: 0; }
.sidebar-foot .account span { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.sidebar-foot .account button { flex: none; font-size: 12px; }
.sidebar-foot .download { display: flex; align-items: center; gap: 10px; padding: 8px 10px; border-radius: 10px; color: inherit; text-decoration: none; border: 1px solid var(--border); background: var(--bg); }
.sidebar-foot .download:hover { border-color: var(--accent); }
.sidebar-foot .download-icon { width: 28px; height: 28px; border-radius: 8px; display: grid; place-items: center; background: var(--accent); color: #fff; font-size: 14px; flex: none; }
.sidebar-foot .download-text { display: flex; flex-direction: column; line-height: 1.25; min-width: 0; }
.sidebar-foot .download-text strong { font-size: 13px; font-weight: 600; }
.group { border-radius: 8px; }
.group > summary { list-style: none; cursor: pointer; user-select: none; display: flex; align-items: center; gap: 6px; padding: 6px 0; font-size: 13px; font-weight: 700; text-transform: uppercase; letter-spacing: .04em; color: var(--text); }
.group > summary::-webkit-details-marker { display: none; }
.group > summary::before { content: ""; width: 0; height: 0; border-left: 5px solid var(--muted); border-top: 4px solid transparent; border-bottom: 4px solid transparent; transition: transform .12s; }
.group[open] > summary::before { transform: rotate(90deg); }
.group > section { margin: 10px 0 0 6px; padding-left: 10px; border-left: 2px solid var(--border); }
.group > section > h2 { font-size: 12px; }
.sidebar h2 { font-size: 13px; text-transform: uppercase; letter-spacing: .04em; color: var(--muted); margin: 0 0 8px; display: flex; align-items: center; }
.brand { padding: 0 8px 10px; font-size: 15px; }
.sidebar-nav { display: flex; flex-direction: column; gap: 2px; }
.nav-item { display: flex; align-items: center; gap: 10px; width: 100%; padding: 8px 10px; border: none; background: none; border-radius: 8px; font-size: 14px; color: var(--text); text-align: left; }
.nav-item:hover { background: var(--bg); }
.nav-item svg { width: 18px; height: 18px; flex: none; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }
.nav-item span { flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.nav-item kbd { font: inherit; font-size: 11px; color: var(--muted); border: 1px solid var(--border); border-radius: 4px; padding: 0 5px; line-height: 1.5; }

.search-overlay { position: fixed; inset: 0; z-index: 50; background: rgba(15, 20, 25, .45); display: flex; justify-content: center; align-items: flex-start; padding-top: 12vh; }
.search-panel { width: min(640px, calc(100vw - 32px)); max-height: 70vh; display: flex; flex-direction: column; background: var(--panel); border: 1px solid var(--border); border-radius: 12px; box-shadow: 0 16px 48px rgba(0, 0, 0, .25); overflow: hidden; }
.search-panel input { padding: 14px 16px; border: 0; border-bottom: 1px solid var(--border); background: var(--panel); color: var(--text); font: inherit; font-size: 15px; outline: none; }
.search-scope { display: flex; gap: 6px; padding: 8px 12px; border-bottom: 1px solid var(--border); }
.search-scope button { padding: 3px 10px; font-size: 12px; border-radius: 999px; border: 1px solid var(--border); background: var(--bg); color: var(--text); margin: 0; }
.search-scope button.active { background: var(--accent); color: var(--accent-text); border-color: var(--accent); }
.search-results { list-style: none; margin: 0; padding: 6px; overflow-y: auto; min-height: 0; }
.search-results:empty { display: none; }
.search-results li { display: flex; align-items: center; gap: 10px; padding: 8px 10px; border-radius: 8px; font-size: 13px; cursor: pointer; min-width: 0; }
.search-results li:hover, .search-results li.active { background: var(--bg); }
.search-results li.empty { cursor: default; color: var(--muted); justify-content: center; }
.search-results .type { flex: none; font-size: 11px; padding: 1px 7px; border-radius: 999px; border: 1px solid var(--border); color: var(--muted); }
.search-results .name { flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.search-results .date { flex: none; color: var(--muted); font-size: 11px; font-variant-numeric: tabular-nums; }
.grow { flex: 1; }
.list { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 4px; }
.list.samples { margin-top: 8px; }
.list li { display: flex; justify-content: space-between; align-items: center; gap: 8px; padding: 6px 8px; border-radius: 6px; font-size: 13px; min-width: 0; }
.list li:hover { background: var(--bg); }
.list li.active { background: var(--user); }
.list li .name { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; flex: 1; cursor: pointer; }
.list li .meta { color: var(--muted); font-size: 11px; }
.list li button.rename { margin-left: 0; visibility: hidden; }
.list li:hover button.rename, .list li.active button.rename { visibility: visible; }
.list li .rename-input { flex: 1; min-width: 0; padding: 2px 6px; border: 1px solid var(--accent); border-radius: 4px; background: var(--panel); color: var(--text); font: inherit; font-size: 13px; }

.chat { display: flex; flex-direction: column; height: 100vh; min-width: 0; --gutter: max(24px, calc((100% - 820px) / 2)); }
/* Empty chat: heading, composer and examples sit together in the middle of the screen. */
.chat.empty { justify-content: center; }
.chat.empty .messages { flex: 0 0 auto; overflow: visible; padding-bottom: 8px; }
.chat.empty .composer, .chat.empty .examples { border-top: none; background: transparent; }
.chat.empty .composer-box { background: var(--panel); }
.messages { flex: 1; overflow-y: auto; padding: 24px var(--gutter); display: flex; flex-direction: column; gap: 12px; }
.messages > * { flex-shrink: 0; } /* a fixed-height flex column would otherwise squeeze items with an explicit min-height */
.welcome { margin: auto; text-align: center; display: flex; flex-direction: column; gap: 10px; }
.welcome h1 { font-size: 26px; margin: 0; }
.examples { padding: 0 var(--gutter) 18px; display: flex; flex-direction: column; gap: 2px; background: var(--panel); }
.example { display: flex; align-items: center; gap: 12px; padding: 8px 10px; border: none; border-radius: 8px; background: none; color: var(--text); font-size: 14px; text-align: left; min-width: 0; }
.example:hover { background: var(--bg); }
.example-icon { flex: none; width: 22px; height: 22px; border-radius: 6px; display: grid; place-items: center; font-size: 11px; font-weight: 700; color: var(--accent); background: color-mix(in srgb, var(--accent) 12%, transparent); }
.example-text { flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }

.msg { max-width: 860px; padding: 10px 14px; border-radius: 10px; line-height: 1.55; font-size: 14px; }
.msg.user { background: var(--user); align-self: flex-end; white-space: pre-wrap; }
.msg.assistant { background: var(--panel); border: 1px solid var(--border); align-self: flex-start; width: min(860px, 100%); }
.msg.assistant p:first-child { margin-top: 0; }
.msg.assistant p:last-child { margin-bottom: 0; }
.msg.assistant table { border-collapse: collapse; margin: 8px 0; display: block; overflow-x: auto; }
.msg.assistant th, .msg.assistant td { border: 1px solid var(--border); padding: 4px 8px; font-size: 13px; white-space: nowrap; }
.msg.assistant th { background: var(--tool); }
.msg.assistant pre { background: var(--tool); padding: 8px; border-radius: 6px; overflow-x: auto; }
.msg.assistant code { font-size: 13px; }
.msg.error { background: transparent; color: var(--error); border: 1px solid var(--error); align-self: flex-start; min-height: auto; white-space: pre-wrap; }

.thinking { align-self: flex-start; max-width: 860px; font-size: 13px; color: var(--muted); }
.thinking summary { cursor: pointer; }
.thinking-body { white-space: pre-wrap; padding: 6px 10px; border-left: 2px solid var(--border); margin-top: 4px; max-height: 240px; overflow: auto; }

.tool { align-self: flex-start; max-width: 860px; background: var(--tool); border: 1px solid var(--border); border-radius: 8px; font-size: 13px; }
.tool summary { padding: 6px 10px; cursor: pointer; display: flex; gap: 8px; align-items: center; }
.tool summary .status { font-size: 11px; padding: 1px 6px; border-radius: 10px; border: 1px solid var(--border); color: var(--muted); }
.tool summary .status.ok { color: var(--ok); }
.tool summary .status.error { color: var(--error); }
.tool pre { margin: 0; padding: 8px 10px; border-top: 1px solid var(--border); white-space: pre-wrap; word-break: break-all; max-height: 240px; overflow: auto; }
.tool img { display: block; max-width: 100%; border-top: 1px solid var(--border); }

.chart { margin: 10px 0; padding: 10px; border: 1px solid var(--border); border-radius: 8px; background: var(--bg); }
.chart-title { font-weight: 600; font-size: 13px; margin-bottom: 6px; }
.chart canvas { max-height: 320px; }
.choices { margin: 10px 0 0; padding-top: 8px; border-top: 1px dashed var(--border); }
.choices-question { font-weight: 600; margin-bottom: 6px; }
.choices-row { display: flex; flex-wrap: wrap; gap: 8px; }
.choice { border-radius: 999px; padding: 6px 14px; }
.choice:hover:not([disabled]) { border-color: var(--accent); color: var(--accent); }
.choice.picked { background: var(--accent); color: var(--accent-text); border-color: var(--accent); }

.status { padding: 2px calc(var(--gutter) + 12px) 0; font-size: 12px; color: var(--muted); }
.status.working { display: flex; align-items: center; gap: 8px; }
.status.working::before { content: ""; width: 8px; height: 8px; border-radius: 999px; background: var(--accent); animation: status-pulse 1.1s ease-in-out infinite; }
@keyframes status-pulse { 0%, 100% { opacity: .25; transform: scale(.8); } 50% { opacity: 1; transform: scale(1.15); } }
.turn-actions { align-self: flex-start; max-width: 860px; width: min(860px, 100%); font-size: 12px; color: var(--muted); display: flex; gap: 8px; align-items: center; margin-top: -6px; }
.turn-actions button.link { font-size: 12px; }
.correction { align-self: flex-start; width: min(860px, 100%); background: var(--panel); border: 1px dashed var(--warn); border-radius: 10px; padding: 10px 14px; display: flex; flex-direction: column; gap: 6px; font-size: 13px; }
.correction label { display: flex; flex-direction: column; gap: 3px; color: var(--muted); }
.correction textarea { resize: vertical; padding: 6px 8px; border: 1px solid var(--border); border-radius: 6px; background: var(--bg); color: var(--text); font: inherit; font-size: 13px; }
.correction .row { display: flex; gap: 8px; align-items: center; }
.correction .saved { color: var(--ok); }
.composer { padding: 8px var(--gutter) 18px; border-top: 1px solid var(--border); background: var(--panel); }
.chat:has(#examples:not(.hidden)) .composer { padding-bottom: 6px; }
.composer-box { display: flex; flex-direction: column; gap: 6px; padding: 10px 12px 8px; border: 1px solid var(--border); border-radius: 14px; background: var(--bg); transition: border-color .12s, box-shadow .12s; }
.composer-box:focus-within { border-color: var(--accent); box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 18%, transparent); }
.composer.dragging .composer-box { border-style: dashed; border-color: var(--accent); }
.composer textarea { width: 100%; min-height: 24px; max-height: 220px; resize: none; padding: 2px 0; border: 0; background: transparent; color: var(--text); font: inherit; line-height: 1.45; outline: none; }
.composer-actions { display: flex; align-items: center; gap: 8px; }
.composer-hint { flex: 1; font-size: 11px; color: var(--muted); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.composer-btn { display: inline-flex; width: 32px; height: 32px; align-items: center; justify-content: center; padding: 0; border: 0; border-radius: 999px; }
.composer-btn--send { background: var(--accent); color: var(--accent-text); }
.composer-btn--send:hover:not([disabled]) { filter: brightness(1.08); }
.composer-btn--send[disabled] { opacity: .35; cursor: default; }
.composer-btn--stop { background: var(--text); color: var(--panel); }
.composer-btn--stop:hover { opacity: .85; }
.attachments { display: flex; flex-wrap: wrap; gap: 8px; }
.attachment { position: relative; width: 96px; height: 64px; border: 1px solid var(--border); border-radius: 8px; overflow: hidden; background: var(--panel); }
.attachment img { width: 100%; height: 100%; object-fit: cover; }
.attachment button { position: absolute; top: 2px; right: 2px; width: 20px; height: 20px; padding: 0; border-radius: 999px; font-size: 12px; line-height: 1; }
.msg.user .user-images { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 8px; }
.msg.user .user-images img { max-width: 260px; max-height: 180px; border-radius: 8px; border: 1px solid var(--border); cursor: zoom-in; }
#stop { border-color: var(--error); color: var(--error); }

.viewer { display: flex; flex-direction: column; height: 100vh; background: var(--panel); border-left: 1px solid var(--border); min-width: 0; position: relative; }
.viewer-resizer { position: absolute; left: -4px; top: 0; bottom: 0; width: 8px; cursor: col-resize; z-index: 2; }
.viewer-resizer:hover, .app.resizing .viewer-resizer { background: color-mix(in srgb, var(--accent) 35%, transparent); }
.app.resizing { user-select: none; cursor: col-resize; }
.app.resizing .viewer-body img { pointer-events: none; }
/* Dragging past the right edge: the panel fades into a "ghost" and snaps closed on release (like docking a window). */
.viewer.will-close { opacity: .35; outline: 2px dashed var(--accent); outline-offset: -2px; transition: opacity .12s; }
.viewer.will-close::after { content: "Release to close"; position: absolute; inset: 0; display: flex; align-items: center; justify-content: center; font-weight: 600; color: var(--accent); background: var(--panel); opacity: .9; }
.viewer-head { display: flex; align-items: center; justify-content: space-between; gap: 8px; padding: 12px 14px; border-bottom: 1px solid var(--border); font-size: 14px; }
.viewer-head strong { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.viewer-actions { display: flex; gap: 6px; align-items: center; flex: none; }
.viewer-actions .small { margin-left: 0; }
a.button-link { display: inline-block; border: 1px solid var(--border); border-radius: 6px; padding: 2px 8px; font-size: 12px; color: var(--text); text-decoration: none; background: var(--panel); }
a.button-link:hover { border-color: var(--accent); color: var(--accent); }
.viewer-search { display: flex; gap: 6px; padding: 8px 14px 0; }
.viewer-search input { flex: 1; padding: 6px 8px; border: 1px solid var(--border); border-radius: 6px; background: var(--bg); color: var(--text); font: inherit; }
.viewer-hits { padding: 6px 14px 0; max-height: 200px; overflow-y: auto; }
.viewer-hits li { display: block; cursor: pointer; }
.viewer-hits .hit-page { color: var(--accent); font-weight: 600; margin-right: 6px; }
.viewer-hits .hit-snippet { color: var(--muted); font-size: 12px; }
.viewer-nav { display: flex; align-items: center; gap: 6px; padding: 8px 14px; border-bottom: 1px solid var(--border); }
.viewer-nav input { width: 64px; padding: 4px 6px; border: 1px solid var(--border); border-radius: 6px; background: var(--bg); color: var(--text); font: inherit; }
.viewer-nav .small { margin-left: 0; }
.viewer-body { flex: 1; overflow: auto; padding: 10px 14px 16px; }
.viewer-body img { display: block; width: 100%; height: auto; border: 1px solid var(--border); border-radius: 4px; background: #fff; }
.viewer-body pre { white-space: pre-wrap; font: 13px/1.5 "Segoe UI", system-ui, sans-serif; margin: 0; }
.dashboard-frame { flex: 1; width: 100%; border: 0; background: var(--bg); }
.count { font-size: 11px; padding: 1px 7px; border-radius: 10px; background: var(--user); color: var(--text); text-transform: none; letter-spacing: 0; }
.corrections { display: flex; flex-direction: column; gap: 10px; }
.corrections .viewer-search { padding: 0; }
.lessons { display: flex; flex-direction: column; gap: 10px; }
.lesson { border: 1px solid var(--border); border-radius: 10px; padding: 10px 12px; font-size: 13px; display: flex; flex-direction: column; gap: 6px; background: var(--bg); }
.lesson .lesson-head { display: flex; justify-content: space-between; align-items: center; gap: 8px; color: var(--muted); font-size: 12px; }
.lesson .lesson-head .small { margin-left: 0; }
.lesson .field { display: grid; grid-template-columns: 64px 1fr; gap: 6px; }
.lesson .field b { color: var(--muted); font-weight: 600; font-size: 12px; }
.lesson .field.correct b { color: var(--ok); }
.lesson .field.wrong b { color: var(--error); }
.lesson .field span { white-space: pre-wrap; word-break: break-word; }
.lesson .tools { color: var(--muted); font-size: 12px; }
.list li.manual { display: block; cursor: pointer; }
.list li.manual .name { display: block; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.list li.manual .meta { display: block; }

@media (max-width: 800px) {
  .app.with-viewer { grid-template-columns: 1fr; }
  .viewer { position: fixed; inset: 0; z-index: 10; }
  .app { grid-template-columns: 1fr; }
  .sidebar { display: none; }
  .messages { padding: 16px; }
  .composer { padding: 8px 12px 14px; }
}