:root{
  --bg-0:#0b0d12;
  --bg-1:#12141b;
  --bg-2:#181b24;
  --bg-3:#1f2330;
  --border:#262a36;
  --text-0:#f2f3f5;
  --text-1:#a9adba;
  --text-2:#6b7080;
  --accent:#3b6cf6;
  --accent-hover:#5a82f9;
  --green:#22c55e;
  --danger:#f04747;
  --radius:12px;
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
}

*{box-sizing:border-box;}
html,body{height:100%;}
body{
  margin:0;
  background:var(--bg-0);
  color:var(--text-0);
}

/* ---------- Auth page ---------- */
.auth-body{
  display:flex;
  align-items:center;
  justify-content:center;
  min-height:100vh;
  padding:20px;
  background:radial-gradient(circle at 50% 0%, #14192b 0%, #0b0d12 60%);
}
.auth-card{
  width:100%;
  max-width:400px;
  background:var(--bg-1);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:32px 28px;
}
.brand{text-align:center;margin-bottom:24px;}
.brand-logo{
  width:56px;height:56px;border-radius:16px;
  background:linear-gradient(135deg,var(--accent),#7b3bf6);
  display:flex;align-items:center;justify-content:center;
  font-weight:800;letter-spacing:1px;color:#fff;
  margin:0 auto 12px;
  font-size:18px;
}
.brand-logo.small{width:32px;height:32px;font-size:11px;border-radius:9px;margin:0;}
.brand h1{font-size:20px;margin:0 0 4px;}
.subtitle{color:var(--text-1);font-size:13px;margin:0;}

.tabs{display:flex;gap:6px;background:var(--bg-2);padding:4px;border-radius:10px;margin-bottom:20px;}
.tab-btn{
  flex:1;padding:9px;border:none;background:transparent;color:var(--text-1);
  border-radius:8px;cursor:pointer;font-weight:600;font-size:13px;
}
.tab-btn.active{background:var(--accent);color:#fff;}

.auth-form{display:flex;flex-direction:column;gap:8px;}
.auth-form.hidden{display:none;}
.auth-form label{font-size:12px;color:var(--text-1);margin-top:8px;}
.auth-form input{
  background:var(--bg-2);border:1px solid var(--border);color:var(--text-0);
  padding:11px 12px;border-radius:9px;font-size:14px;outline:none;
}
.auth-form input:focus{border-color:var(--accent);}
.primary-btn{
  margin-top:16px;background:var(--accent);color:#fff;border:none;
  padding:12px;border-radius:9px;font-weight:700;font-size:14px;cursor:pointer;
}
.primary-btn:hover{background:var(--accent-hover);}
.error-msg{color:var(--danger);font-size:12.5px;min-height:16px;margin:6px 0 0;}

/* ---------- App shell ---------- */
.app-body{overflow:hidden;}
.app-shell{display:flex;height:100vh;}

.sidebar{
  width:270px;flex-shrink:0;background:var(--bg-1);border-right:1px solid var(--border);
  display:flex;flex-direction:column;padding:16px;
}
.sidebar-header{display:flex;align-items:center;justify-content:space-between;margin-bottom:16px;}
.brand-mini{display:flex;align-items:center;gap:10px;font-weight:700;font-size:14px;}

.new-conv-btn{
  background:var(--bg-2);border:1px solid var(--border);color:var(--text-0);
  padding:10px;border-radius:9px;cursor:pointer;font-weight:600;font-size:13px;margin-bottom:14px;
}
.new-conv-btn:hover{border-color:var(--accent);}

.conv-list{flex:1;overflow-y:auto;display:flex;flex-direction:column;gap:4px;}
.conv-item{
  padding:10px 12px;border-radius:8px;cursor:pointer;font-size:13px;color:var(--text-1);
  white-space:nowrap;overflow:hidden;text-overflow:ellipsis;
}
.conv-item:hover{background:var(--bg-2);}
.conv-item.active{background:var(--bg-3);color:var(--text-0);}

.sidebar-footer{
  display:flex;align-items:center;justify-content:space-between;
  padding-top:12px;border-top:1px solid var(--border);font-size:13px;color:var(--text-1);
}
.link-btn{background:none;border:none;color:var(--accent);cursor:pointer;font-size:12.5px;font-weight:600;}

.main-area{flex:1;display:flex;flex-direction:column;min-width:0;}

.topbar{
  display:flex;align-items:center;gap:14px;padding:14px 22px;border-bottom:1px solid var(--border);
  background:var(--bg-1);
}
.status-dot{width:8px;height:8px;border-radius:50%;background:var(--green);display:inline-block;margin-right:6px;}
.topbar-title{display:flex;align-items:center;gap:6px;flex:1;font-size:14px;}
.topbar-sub{color:var(--text-2);font-size:12.5px;margin-left:8px;}
.topbar-user{font-size:13px;color:var(--text-1);}

.chat-area{flex:1;overflow-y:auto;padding:24px;}
.empty-state{
  height:100%;display:flex;flex-direction:column;align-items:center;justify-content:center;
  color:var(--text-2);text-align:center;
}
.empty-icon{font-size:38px;margin-bottom:10px;}
.empty-state h2{color:var(--text-1);font-size:18px;margin:0 0 6px;}
.empty-state.hidden{display:none;}

.messages{max-width:820px;margin:0 auto;display:flex;flex-direction:column;gap:16px;}
.msg{padding:14px 16px;border-radius:12px;font-size:14px;line-height:1.55;max-width:85%;}
.msg.user{align-self:flex-end;background:var(--accent);color:#fff;border-bottom-right-radius:4px;}
.msg.assistant{align-self:flex-start;background:var(--bg-2);border:1px solid var(--border);border-bottom-left-radius:4px;white-space:pre-wrap;}
.msg pre{
  background:#0d0f16;border:1px solid var(--border);border-radius:8px;
  padding:12px;overflow-x:auto;font-size:12.5px;
}
.msg.loading{color:var(--text-2);font-style:italic;}

.prompt-bar{
  display:flex;gap:10px;padding:16px 22px;border-top:1px solid var(--border);background:var(--bg-1);
}
.prompt-bar textarea{
  flex:1;resize:none;max-height:140px;background:var(--bg-2);border:1px solid var(--border);
  color:var(--text-0);border-radius:10px;padding:12px 14px;font-size:14px;outline:none;font-family:inherit;
}
.prompt-bar textarea:focus{border-color:var(--accent);}
.send-btn{
  background:#fff;color:#0b0d12;border:none;padding:0 20px;border-radius:10px;
  font-weight:700;cursor:pointer;font-size:14px;
}
.send-btn:disabled{opacity:.5;cursor:not-allowed;}

.icon-btn{background:none;border:none;color:var(--text-1);font-size:18px;cursor:pointer;}
.only-mobile{display:none;}

@media (max-width: 860px){
  .only-mobile{display:block;}
  .sidebar{
    position:fixed;inset:0 auto 0 0;z-index:20;transform:translateX(-100%);
    transition:transform .2s ease;width:80%;max-width:300px;
  }
  .sidebar.open{transform:translateX(0);}
  .topbar-sub{display:none;}
}