:root{
  --navy:#0d1160; --navy2:#131a7d; --blue:#1464f4; --cyan:#36bffa;
  --ink:#171a26; --mut:#5b6070; --line:#e3e6ef; --bg:#f4f6fb; --card:#ffffff;
  --bubble:#eef2ff; --radius:16px;
}
*{box-sizing:border-box}
html,body{height:100%}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;background:var(--bg);color:var(--ink)}
button{font:inherit;cursor:pointer}
input,textarea{font:inherit}
.hidden{display:none!important}

/* ---------- login ---------- */
.login-wrap{min-height:100dvh;display:flex;align-items:center;justify-content:center;padding:20px;background:linear-gradient(160deg,var(--navy) 0%,var(--navy2) 55%,var(--blue) 130%)}
.login-card{background:var(--card);border-radius:22px;padding:34px 30px;width:100%;max-width:400px;box-shadow:0 24px 60px rgba(0,0,20,.35)}
.login-card .mark{display:flex;align-items:center;gap:12px;margin-bottom:6px}
.login-card .mark img{width:52px;height:52px;border-radius:14px}
.login-card .mark b{font-size:26px;color:var(--navy);letter-spacing:.2px}
.login-card .mark span{display:block;font-size:12.5px;color:var(--mut);font-weight:600}
.login-card p.sub{color:var(--mut);font-size:14.5px;line-height:1.5;margin:10px 0 20px}
.field{margin-bottom:14px}
.field label{display:block;font-size:13px;font-weight:700;color:var(--navy);margin-bottom:6px}
.field input{width:100%;padding:12px 14px;border:1.5px solid var(--line);border-radius:12px;font-size:16px;background:#fbfcff}
.field input:focus{outline:none;border-color:var(--blue);box-shadow:0 0 0 3px rgba(20,100,244,.15)}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;border:none;border-radius:12px;padding:12px 18px;font-weight:700;font-size:15px;background:var(--blue);color:#fff}
.btn:hover{background:#0f53d6}
.btn:disabled{opacity:.6;cursor:default}
.btn.block{width:100%}
.btn.ghost{background:#fff;color:var(--navy);border:1.5px solid var(--line)}
.btn.ghost:hover{border-color:var(--blue);color:var(--blue)}
.err{background:#fdecec;color:#9c1c1c;border:1px solid #f5c2c2;border-radius:10px;padding:9px 12px;font-size:13.5px;margin-bottom:12px}
.login-foot{margin-top:16px;text-align:center;color:var(--mut);font-size:12.5px}

/* ---------- shell ---------- */
.shell{display:flex;height:100dvh;overflow:hidden}
.side{width:290px;flex:0 0 290px;background:var(--navy);color:#dfe4ff;display:flex;flex-direction:column;padding:16px 12px;z-index:30}
.side .brand{display:flex;align-items:center;gap:10px;padding:2px 8px 14px}
.side .brand img{width:38px;height:38px;border-radius:10px}
.side .brand b{color:#fff;font-size:19px}
.side .brand span{display:block;font-size:11px;color:#9fb0ff;font-weight:600}
.newchat{margin:2px 4px 12px;background:var(--blue);color:#fff;border:none;border-radius:11px;padding:11px;font-weight:700;font-size:14.5px}
.newchat:hover{background:#2f74f7}
.convlist{flex:1;overflow-y:auto;display:flex;flex-direction:column;gap:2px;padding-right:2px}
.conv{display:flex;align-items:center;gap:6px;padding:9px 10px;border-radius:10px;color:#dfe4ff;font-size:14px;cursor:pointer;border:1px solid transparent}
.conv:hover{background:rgba(255,255,255,.07)}
.conv.on{background:rgba(54,191,250,.16);border-color:rgba(54,191,250,.35);color:#fff}
.conv .t{flex:1;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.conv .del{background:none;border:none;color:#8fa0e8;font-size:15px;padding:2px 4px;border-radius:6px}
.conv .del:hover{color:#fff;background:rgba(255,255,255,.12)}
.side .who{border-top:1px solid rgba(255,255,255,.14);padding:12px 8px 2px;display:flex;align-items:center;gap:10px}
.side .who .av{width:34px;height:34px;border-radius:50%;background:var(--cyan);color:var(--navy);display:flex;align-items:center;justify-content:center;font-weight:800;font-size:14px}
.side .who .n{flex:1;min-width:0}
.side .who .n b{color:#fff;font-size:14px;display:block;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.side .who .n span{font-size:11.5px;color:#9fb0ff;text-transform:capitalize}
.signout{background:none;border:1px solid rgba(255,255,255,.25);color:#dfe4ff;border-radius:9px;padding:7px 10px;font-size:12.5px;font-weight:700}
.signout:hover{background:rgba(255,255,255,.1)}

.main{flex:1;display:flex;flex-direction:column;min-width:0;background:var(--bg)}
.topbar{display:none;align-items:center;gap:10px;background:var(--navy);color:#fff;padding:10px 14px}
.topbar img{width:30px;height:30px;border-radius:8px}
.topbar b{font-size:16.5px}
.topbar .menubtn{margin-left:auto;background:rgba(255,255,255,.12);border:none;color:#fff;border-radius:9px;padding:8px 12px;font-weight:700;font-size:13.5px}
.msgs{flex:1;overflow-y:auto;padding:22px 16px 12px}
.msgs-in{max-width:820px;margin:0 auto;display:flex;flex-direction:column;gap:14px}
.empty{max-width:640px;margin:8vh auto 0;text-align:center;color:var(--mut);padding:0 10px}
.empty img{width:76px;height:76px;border-radius:20px;margin-bottom:14px}
.empty h1{color:var(--navy);font-size:26px;margin:0 0 8px}
.empty p{font-size:15px;line-height:1.6;margin:0 0 18px}
.chips{display:flex;flex-wrap:wrap;gap:8px;justify-content:center}
.chip{background:#fff;border:1.5px solid var(--line);border-radius:999px;padding:9px 14px;font-size:13.5px;font-weight:600;color:var(--navy)}
.chip:hover{border-color:var(--blue);color:var(--blue)}
.msg{display:flex;gap:10px;max-width:100%}
.msg .av{flex:0 0 32px;width:32px;height:32px;border-radius:50%;display:flex;align-items:center;justify-content:center;font-weight:800;font-size:12.5px;margin-top:2px}
.msg.user{flex-direction:row-reverse}
.msg.user .av{background:var(--blue);color:#fff}
.msg.assistant .av{background:var(--navy);color:#fff}
.msg .body{background:var(--card);border:1px solid var(--line);border-radius:4px 16px 16px 16px;padding:12px 15px;font-size:15px;line-height:1.62;min-width:0;max-width:calc(100% - 46px);overflow-wrap:anywhere}
.msg.user .body{background:var(--bubble);border-color:#d7deff;border-radius:16px 4px 16px 16px}
.msg .body p{margin:0 0 9px}
.msg .body p:last-child{margin-bottom:0}
.msg .body ul,.msg .body ol{margin:4px 0 9px;padding-left:20px}
.msg .body li{margin:3px 0}
.msg .body h3,.msg .body h4{color:var(--navy);margin:12px 0 6px;font-size:15.5px}
.msg .body code{background:#eef1fa;border-radius:6px;padding:1px 5px;font-size:13px}
.msg .body a{color:var(--blue)}
.tools{display:flex;flex-wrap:wrap;gap:6px;margin-top:9px}
.tool{font-size:11.5px;font-weight:700;background:#eaf6fe;color:#0b5cad;border:1px solid #cdeafd;border-radius:999px;padding:3px 9px}
.typing{display:inline-flex;gap:5px;padding:4px 2px}
.typing i{width:7px;height:7px;border-radius:50%;background:#9db4f5;animation:bl 1.1s infinite}
.typing i:nth-child(2){animation-delay:.15s}.typing i:nth-child(3){animation-delay:.3s}
@keyframes bl{0%,80%,100%{opacity:.3}40%{opacity:1}}
.composer{border-top:1px solid var(--line);background:#fff;padding:12px 16px calc(12px + env(safe-area-inset-bottom))}
.composer-in{max-width:820px;margin:0 auto;display:flex;gap:10px;align-items:flex-end}
.composer textarea{flex:1;resize:none;border:1.5px solid var(--line);border-radius:14px;padding:12px 14px;font-size:16px;max-height:140px;background:#fbfcff;line-height:1.45}
.composer textarea:focus{outline:none;border-color:var(--blue);box-shadow:0 0 0 3px rgba(20,100,244,.13)}
.sendbtn{flex:0 0 auto;background:var(--blue);color:#fff;border:none;border-radius:14px;padding:12px 20px;font-weight:800;font-size:15px}
.sendbtn:hover{background:#0f53d6}
.sendbtn:disabled{opacity:.55}
.composer .hint{max-width:820px;margin:8px auto 0;font-size:12px;color:var(--mut);text-align:center}
#toast-root{position:fixed;left:50%;bottom:26px;transform:translateX(-50%);z-index:99;display:flex;flex-direction:column;gap:8px;align-items:center}
.toast{background:var(--navy);color:#fff;border-radius:11px;padding:10px 16px;font-size:14px;box-shadow:0 10px 30px rgba(0,0,30,.3)}

@media (max-width:760px){
  .topbar{display:flex}
  .side{position:fixed;top:0;bottom:0;left:0;transform:translateX(-105%);transition:transform .22s ease;box-shadow:0 0 50px rgba(0,0,20,.4)}
  .side.open{transform:translateX(0)}
  .scrim{position:fixed;inset:0;background:rgba(5,8,40,.45);z-index:20}
  .msgs{padding:16px 12px 10px}
  .msg .body{font-size:14.5px}
}