:root { --bg:#0f1115; --panel:#171a21; --border:#262b36; --text:#e6e8ee; --muted:#8a93a5; --accent:#4c8dff; --green:#2ecc71; --red:#ff6b6b; }
* { box-sizing:border-box; }
body { margin:0; font:15px/1.5 -apple-system,Segoe UI,Roboto,sans-serif; background:var(--bg); color:var(--text); height:100vh; }

/* buttons / inputs */
button, .signin-btn { background:var(--accent); color:#fff; border:0; border-radius:8px; padding:9px 14px; font-size:14px; cursor:pointer; text-decoration:none; text-align:center; }
button.secondary { background:var(--panel); border:1px solid var(--border); }
button.danger { background:transparent; color:var(--red); border:1px solid var(--red); }
input, textarea, select { background:#0c0e12; color:var(--text); border:1px solid var(--border); border-radius:8px; padding:10px; font-size:14px; font-family:inherit; }
a { color:var(--accent); }

/* screens */
.screen { display:none; height:100%; }
.screen.active { display:flex; }
#login { align-items:center; justify-content:center; }
#login .card { background:var(--panel); border:1px solid var(--border); border-radius:12px; padding:28px; width:340px; }
#login h1 { font-size:18px; margin:0 0 4px; }
#login p { color:var(--muted); margin:0 0 16px; }

/* student chat shell */
#main { flex-direction:column; }
header { display:flex; align-items:center; gap:12px; padding:12px 18px; border-bottom:1px solid var(--border); background:var(--panel); }
header .name { font-weight:600; }
header .meta { color:var(--muted); font-size:13px; flex:1; }
#body { display:flex; flex:1; min-height:0; }
#sidebar { width:280px; border-right:1px solid var(--border); display:flex; flex-direction:column; background:var(--panel); }
#sidebar .actions { padding:12px; display:flex; gap:8px; }
#sessions { overflow-y:auto; flex:1; }
#chat { flex:1; display:flex; flex-direction:column; min-width:0; }
#messages { flex:1; overflow-y:auto; padding:18px; min-height:0; }
#compose { display:flex; gap:8px; padding:14px 18px; border-top:1px solid var(--border); background:var(--panel); }
#compose textarea { flex:1; resize:none; min-height:44px; }
#restore { display:none; color:var(--muted); font-size:13px; text-align:center; padding:8px 18px; background:var(--panel); border-bottom:1px solid var(--border); }
#scratch-note { display:none; color:var(--green); font-size:13px; text-align:center; padding:8px 18px; background:var(--panel); border-bottom:1px solid var(--border); }

/* conversation list */
.session { display:flex; align-items:center; gap:6px; padding:10px 14px; border-bottom:1px solid var(--border); cursor:pointer; }
.session:hover { background:#1d212b; }
.session .t { flex:1; min-width:0; overflow:hidden; text-overflow:ellipsis; white-space:nowrap; font-weight:500; }
.session .m { color:var(--muted); font-size:12px; }
.menu-btn { background:none; border:none; color:var(--muted); font-size:15px; padding:2px 6px; cursor:pointer; }
.menu-btn:hover { color:var(--text); }
.menu-pop { position:absolute; background:var(--panel); border:1px solid var(--border); border-radius:8px; padding:4px; box-shadow:0 4px 16px rgba(0,0,0,.35); z-index:20; }
.menu-pop button { display:block; background:none; border:none; color:var(--text); font-size:13px; padding:6px 12px; border-radius:6px; text-align:left; width:100%; cursor:pointer; }
.menu-pop button:hover { background:#1d212b; }
.menu-pop button.danger { color:var(--red); }

/* chat messages */
.msg { max-width:760px; margin:0 auto 14px; }
.msg .role { font-size:12px; color:var(--muted); margin-bottom:3px; }
.msg .bubble { background:var(--panel); border:1px solid var(--border); border-radius:10px; padding:10px 12px; word-wrap:break-word; }
.msg.user .bubble { background:#20304f; border-color:#2c4470; white-space:pre-wrap; }
.msg .bubble > :first-child { margin-top:0; }
.msg .bubble > :last-child { margin-bottom:0; }
.msg .bubble pre { background:#0c0e12; border:1px solid var(--border); border-radius:8px; padding:10px; overflow-x:auto; margin:8px 0; }
.msg .bubble pre code { background:none; padding:0; border:none; }
.msg .bubble code { background:#0c0e12; border:1px solid var(--border); border-radius:4px; padding:1px 4px; font-size:13px; }
.msg .bubble .code-label { font-size:11px; color:var(--muted); text-transform:uppercase; letter-spacing:.05em; margin:8px 0 4px; }
.msg .bubble table { border-collapse:collapse; margin:8px 0; display:block; overflow-x:auto; max-width:100%; }
.msg .bubble th, .msg .bubble td { border:1px solid var(--border); padding:4px 8px; }
.msg .cost { font-size:12px; color:var(--muted); margin-top:4px; }
.error { color:var(--red); }

/* inline offers (new-topic suggestion, session-size-cap continuation) */
.offer { max-width:760px; margin:0 auto 14px; background:var(--panel); border:1px solid var(--border); border-left:3px solid var(--accent); border-radius:10px; padding:10px 12px; color:var(--muted); font-size:13px; }
.offer button { margin:8px 8px 0 0; padding:7px 12px; font-size:13px; }

/* typing indicator: three dots, accent color sweeps left to right */
.typing { display:inline-flex; gap:6px; align-items:center; padding:2px 0; }
.typing i { width:7px; height:7px; border-radius:50%; background:var(--muted); animation:typing-pulse 1.4s ease-in-out infinite; }
.typing i:nth-child(2) { animation-delay:.2s; }
.typing i:nth-child(3) { animation-delay:.4s; }
@keyframes typing-pulse {
  0%, 100% { background:var(--muted); transform:scale(1); }
  50% { background:var(--accent); transform:scale(1.3); }
}
@media (prefers-reduced-motion: reduce) {
  .typing i { animation:none; }
}

/* admin dashboard */
#admin { flex-direction:column; min-width:0; height:100%; }
#admin .tabbar { display:flex; gap:8px; padding:10px 16px; border-bottom:1px solid var(--border); background:var(--panel); }
#admin .tabbar button { background:none; border:1px solid transparent; color:var(--muted); padding:8px 16px; font-size:14px; }
#admin .tabbar button.active { background:var(--panel); border-color:var(--border); color:var(--text); border-radius:8px; }
#admin .layout { display:grid; grid-template-columns: 1fr; flex:1; min-height:0; }
#admin .pane { display:none; flex-direction:column; min-height:0; min-width:0; }
#admin .pane.active { display:flex; }
#admin .pane-head { padding:12px 16px; border-bottom:1px solid var(--border); font-weight:600; display:flex; gap:8px; align-items:center; }
#admin .pane-head .grow { flex:1; }
#admin .pane-head select { max-width:280px; }
#admin .scroller { overflow-y:auto; flex:1; min-height:0; }
#notice, .notice { color:var(--muted); text-align:center; padding:18px; }
#admin .pane-head .btn { background:none; border:none; color:var(--accent); cursor:pointer; font-size:13px; padding:4px 8px; }
table.data { width:100%; border-collapse:collapse; }
table.data th { text-align:left; color:var(--muted); font-size:12px; font-weight:600; padding:8px 12px; border-bottom:1px solid var(--border); }
table.data td { padding:8px 12px; border-bottom:1px solid var(--border); vertical-align:middle; }
table.data .num { text-align:right; font-variant-numeric:tabular-nums; }
table.data tr.clickable { cursor:pointer; }
table.data tr.clickable:hover { background:#1d212b; }
tr.strike td { opacity:.45; }
.usr { font-size:12px; color:var(--muted); }
.tag { display:inline-block; font-size:11px; padding:1px 8px; border-radius:10px; border:1px solid var(--border); color:var(--muted); }
.tag.draft { color:#e5c07b; }
.tag.deleted { color:var(--red); }
.badge { display:inline-block; min-width:48px; text-align:center; font-size:12px; padding:2px 8px; border-radius:8px; }
.badge.on { background:rgba(46,204,113,.15); color:var(--green); }
.badge.off { background:rgba(255,107,107,.15); color:var(--red); }
.meter { background:#0c0e12; border:1px solid var(--border); border-radius:8px; height:6px; width:70px; overflow:hidden; }
.meter i { display:block; height:100%; background:var(--accent); }
.meter i.warn { background:#e5c07b; }
.meter i.over { background:var(--red); }
.meter-cell { display:inline-flex; align-items:center; gap:8px; }
.meter-label { color:var(--muted); font-size:12px; font-variant-numeric:tabular-nums; white-space:nowrap; }
form.row { display:flex; gap:8px; padding:12px 16px; border-bottom:1px solid var(--border); }
form.row input[type=number] { width:90px; }