:root{--bg:#0b1020;--panel:#111827;--panel2:#1f2937;--line:#334155;--text:#e5e7eb;--muted:#94a3b8;--accent:#10a37f}
*{box-sizing:border-box} body{margin:0;font-family:Segoe UI,Arial,sans-serif;background:var(--bg);color:var(--text)}
.app{display:grid;grid-template-columns:250px 1fr;height:100vh}
.sidebar{border-right:1px solid var(--line);padding:16px;background:#0f172a}.brand{font-size:28px;font-weight:700;margin-bottom:20px}
.ghost{width:100%;padding:12px;border:1px solid var(--line);background:transparent;color:var(--text);border-radius:12px;cursor:pointer}
.sidebar-note,.small{margin-top:16px;color:var(--muted);font-size:14px;line-height:1.5}
.main{display:grid;grid-template-rows:auto 1fr auto;min-width:0}
.topbar{display:flex;justify-content:space-between;align-items:center;padding:14px 18px;border-bottom:1px solid var(--line);background:#0f172a}
.title{font-size:20px;font-weight:700}.hint{color:var(--muted);font-size:13px}
.messages{padding:24px;overflow:auto;display:flex;flex-direction:column;gap:16px}
.msg{max-width:920px;padding:16px 18px;border-radius:18px;line-height:1.55;white-space:pre-wrap;word-break:break-word;border:1px solid var(--line)}
.msg.user{align-self:flex-end;background:rgba(29,78,216,.18)} .msg.assistant{align-self:flex-start;background:rgba(15,118,110,.18)} .msg.system{align-self:center;background:rgba(31,41,55,.8);color:var(--muted)} .msg.error{align-self:center;background:rgba(127,29,29,.35)}
.msg .meta{display:block;color:var(--muted);font-size:12px;margin-bottom:8px}
.composer-wrap{padding:16px 20px;border-top:1px solid var(--line);background:#0f172a}.attachments{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:10px}
.att{padding:8px 10px;background:var(--panel2);border:1px solid var(--line);border-radius:10px;font-size:13px;color:var(--muted)}
.composer{display:grid;grid-template-columns:auto 1fr auto;gap:12px;align-items:end}
.upload-btn{display:flex;align-items:center;justify-content:center;width:48px;height:48px;border:1px solid var(--line);border-radius:14px;background:var(--panel2);cursor:pointer}
textarea{resize:none;width:100%;max-height:220px;min-height:48px;padding:13px 14px;background:var(--panel2);color:var(--text);border:1px solid var(--line);border-radius:16px;font:inherit}
button#sendBtn{height:48px;padding:0 18px;border:none;border-radius:14px;background:var(--accent);color:white;font-weight:700;cursor:pointer}
code{background:#08101d;padding:2px 6px;border-radius:6px}
@media (max-width:900px){.app{grid-template-columns:1fr}.sidebar{display:none}}