*{margin:0;padding:0;box-sizing:border-box}
:root{
    --primary:#2563eb;--primary-d:#1e40af;--primary-l:#3b82f6;--primary-bg:#eff6ff;
    --accent:#ea580c;--ok:#059669;--err:#dc2626;--warn:#d97706;
    --g900:#111827;--g800:#1f2937;--g700:#374151;--g600:#4b5563;--g400:#9ca3af;--g200:#e5e7eb;--g100:#f3f4f6;--g50:#f9fafb;
    --r:10px;--r-sm:6px;--r-lg:14px;
    --sh:0 1px 3px rgba(0,0,0,.08);--sh-md:0 4px 12px rgba(0,0,0,.1);--sh-lg:0 12px 32px rgba(0,0,0,.12);
    --t:.2s cubic-bezier(.4,0,.2,1);
}
body{font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,sans-serif;font-size:15px;line-height:1.6;color:var(--g900);background:var(--g50);height:100vh;overflow:hidden}

/* === Login === */
.login-screen{display:flex;align-items:center;justify-content:center;height:100vh;background:linear-gradient(135deg,#1e40af,#2563eb 50%,#3b82f6);background-size:200% 200%;animation:grad 12s ease infinite}
@keyframes grad{0%,100%{background-position:0% 50%}50%{background-position:100% 50%}}
.login-card{background:#fff;padding:48px 40px;border-radius:var(--r-lg);text-align:center;box-shadow:var(--sh-lg);max-width:380px;width:92%}
.login-icon{margin-bottom:20px}
.login-card h1{font-size:26px;color:var(--g900);margin-bottom:6px;font-weight:700}
.login-card>p{color:var(--g600);margin-bottom:28px;font-size:14px}
.login-card input{width:100%;padding:14px 16px;border:1.5px solid var(--g200);border-radius:var(--r);font-size:15px;margin-bottom:14px;outline:none;transition:border var(--t)}
.login-card input:focus{border-color:var(--primary)}
.login-card button{width:100%;padding:14px;background:var(--primary);color:#fff;border:none;border-radius:var(--r);font-size:16px;font-weight:600;cursor:pointer;transition:all var(--t)}
.login-card button:hover{background:var(--primary-d);transform:translateY(-1px);box-shadow:var(--sh-md)}
.login-error{color:var(--err);margin-top:8px;font-size:14px;min-height:20px}

/* === App === */
.app{display:flex;height:100vh}

/* === Sidebar === */
.sidebar{width:260px;background:var(--g900);color:var(--g100);display:flex;flex-direction:column;flex-shrink:0}
.sidebar-header{display:flex;align-items:center;padding:18px 16px;gap:10px;border-bottom:1px solid var(--g800);transition:background var(--t)}
.sidebar-header:hover{background:var(--g800)}
.logo-text{font-weight:700;font-size:17px;color:#fff}
.btn-new-session{margin:14px 12px;padding:12px 16px;background:var(--primary);color:#fff;border:none;border-radius:var(--r);cursor:pointer;font-size:15px;font-weight:600;display:flex;align-items:center;gap:8px;transition:all var(--t)}
.btn-new-session:hover{background:var(--primary-d);transform:translateY(-1px)}
.plus{width:22px;height:22px;background:rgba(255,255,255,.2);border-radius:6px;display:flex;align-items:center;justify-content:center;font-size:16px}
.session-list{flex:1;overflow-y:auto;padding:4px 8px}
.session-item{padding:10px 12px;border-radius:var(--r-sm);cursor:pointer;margin-bottom:2px;transition:background var(--t);display:flex;justify-content:space-between;align-items:center}
.session-item:hover{background:var(--g800)}
.session-item.active{background:var(--primary)}
.session-name{font-size:13px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;flex:1}
.session-meta{font-size:11px;opacity:.5;margin-top:1px}
.session-item .btn-del{opacity:0;background:none;border:none;color:var(--g400);cursor:pointer;font-size:15px;padding:2px 6px;border-radius:4px;transition:opacity var(--t)}
.session-item:hover .btn-del{opacity:1}
.session-item .btn-del:hover{color:var(--err)}
.sidebar-footer{padding:10px 12px;border-top:1px solid var(--g800);position:relative}
.btn-egg{position:absolute;bottom:12px;right:12px;width:24px;height:24px;background:none;border:none;cursor:pointer;font-size:12px;opacity:.3;transition:opacity .2s;padding:0;line-height:1}
.btn-egg:hover{opacity:.8}
.float-emoji{position:fixed;font-size:32px;pointer-events:none;z-index:9999;animation:floatUp 3s ease-out forwards}
@keyframes floatUp{0%{opacity:1;transform:translateY(0) scale(1) rotate(0deg)}50%{opacity:1;transform:translateY(-120px) scale(1.3) rotate(20deg)}100%{opacity:0;transform:translateY(-300px) scale(.6) rotate(-15deg)}}
.btn-logout{width:100%;padding:8px;background:transparent;border:1px solid var(--g700);color:var(--g400);border-radius:var(--r-sm);cursor:pointer;font-size:13px;transition:all var(--t)}
.btn-logout:hover{background:var(--g800);color:var(--g100)}

/* === Landing === */
.landing{display:flex;align-items:flex-start;justify-content:center;height:100%;overflow-y:auto;background:#fff}
.landing-inner{max-width:640px;padding:48px 24px 60px;width:100%}
.landing-hero{text-align:center;margin-bottom:40px}
.landing-hero h2{font-size:28px;font-weight:700;color:var(--g900);margin-bottom:10px}
.hero-sub{font-size:15px;color:var(--g600);max-width:460px;margin:0 auto}

/* Workflow */
.workflow{margin-bottom:48px;display:flex;flex-direction:column;align-items:center;max-width:580px;margin-left:auto;margin-right:auto}
.wf-step{display:flex;align-items:center;gap:12px;width:100%}
.wf-main{flex:1;min-width:0}
.wf-arrow-v{display:flex;justify-content:center;padding:0 0 0 20px}
.wf-node{display:flex;align-items:center;gap:14px;padding:12px 16px;background:var(--g50);border:1.5px solid var(--g200);border-radius:var(--r);transition:all var(--t)}
.wf-node:hover{border-color:var(--primary);background:var(--primary-bg)}
.wf-icon{width:42px;height:42px;border-radius:var(--r-sm);display:flex;align-items:center;justify-content:center;flex-shrink:0}
.wf-user .wf-icon{background:#dbeafe;color:var(--primary)}
.wf-ai .wf-icon{background:#fef3c7;color:var(--warn)}
.wf-check .wf-icon{background:#d1fae5;color:var(--ok)}
.wf-result .wf-icon{background:#dbeafe;color:var(--primary)}
.wf-label{font-size:14px;font-weight:600;color:var(--g900)}
.wf-desc{font-size:12px;color:var(--g600);line-height:1.4}
/* Side cards */
.wf-side{display:flex;align-items:center;gap:6px;flex-shrink:0}
.wf-arrows-h{color:var(--g400);font-size:16px;font-weight:400;user-select:none}
.wf-side-card{display:flex;align-items:center;gap:6px;padding:8px 12px;border-radius:var(--r-sm);font-size:12px;font-weight:500;border:1.5px dashed var(--g200);background:#fff;white-space:nowrap;color:var(--g600)}
.wf-side-card.wf-ask{color:var(--warn);border-color:#fde68a;background:#fffbeb}
.wf-side-card.wf-arb{color:var(--err);border-color:#fecaca;background:#fef2f2}

/* === Chat === */
.main-content{flex:1;display:flex;flex-direction:column;overflow:hidden;min-width:0}
.chat-area{display:flex;flex-direction:column;height:100%;position:relative}

/* Chat header */
.chat-header{display:flex;align-items:center;padding:12px 20px;background:#fff;border-bottom:1px solid var(--g200);flex-shrink:0}
.chat-title-wrap{display:flex;align-items:center;gap:6px;flex:1;min-width:0}
.chat-title{font-weight:600;font-size:16px;color:var(--g900);cursor:default;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.chat-title-input{font-size:16px;font-weight:600;padding:2px 8px;border:1.5px solid var(--primary);border-radius:var(--r-sm);outline:none;width:300px;max-width:60vw}
.btn-rename{background:none;border:none;cursor:pointer;color:var(--g400);padding:4px;border-radius:4px;display:flex;transition:color var(--t)}
.btn-rename:hover{color:var(--primary)}

/* Settings tags (in header, right side) */
.settings-tags{display:flex;align-items:center;gap:5px;flex-wrap:wrap;flex-shrink:0}
.s-tag{padding:3px 9px;background:var(--g100);border-radius:12px;font-size:11px;font-weight:600;color:var(--g600);white-space:nowrap}

/* Messages */
.messages{flex:1;overflow-y:auto;padding:20px;display:flex;flex-direction:column;gap:14px;background:var(--g50)}
.message{max-width:75%;padding:14px 18px;border-radius:var(--r-lg);font-size:15px;line-height:1.7;word-wrap:break-word;animation:msgIn .25s ease}
@keyframes msgIn{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:translateY(0)}}
.message.user{align-self:flex-end;background:var(--primary);color:#fff;border-bottom-right-radius:4px;white-space:pre-wrap}
.message.assistant{align-self:flex-start;background:#fff;border:1px solid var(--g200);border-bottom-left-radius:4px}
.message.system{align-self:center;background:var(--primary-bg);color:var(--g600);font-size:13px;padding:6px 14px;border-radius:20px}
.msg-time{font-size:11px;opacity:.5;margin-top:6px}
.message.user .msg-time{text-align:right}
.msg-attachments{margin-top:10px;display:flex;flex-wrap:wrap;gap:8px}
.msg-attachment{display:inline-flex;align-items:center;gap:6px;padding:8px 14px;background:var(--primary-bg);border:1px solid rgba(37,99,235,.15);border-radius:var(--r);font-size:13px;font-weight:500;color:var(--primary);cursor:pointer;transition:all var(--t)}
.msg-attachment:hover{background:rgba(37,99,235,.15);transform:translateY(-1px)}
.message.user .msg-attachment{background:rgba(255,255,255,.2);border-color:rgba(255,255,255,.2);color:#fff}
.message.user .msg-attachment:hover{background:rgba(255,255,255,.3)}
.message b,.message strong{font-weight:600}
.message .msg-table{width:100%;border-collapse:collapse;margin:10px 0;font-size:14px}
.message .msg-table th,.message .msg-table td{padding:8px 10px;border:1px solid var(--g200);text-align:left}
.message .msg-table th{background:var(--g50);font-weight:600;font-size:13px}
.message ul,.message ol{margin:8px 0 8px 20px}
.message li{margin-bottom:3px}
.message h2,.message h3{margin:12px 0 8px;color:var(--primary-d)}
.message h2{font-size:16px}.message h3{font-size:15px}
.message hr{border:none;border-top:1px solid var(--g200);margin:12px 0}
.typing-indicator{align-self:flex-start;background:#fff;border:1px solid var(--g200);padding:14px 20px;border-radius:var(--r-lg);border-bottom-left-radius:4px}
.typing-dots{display:flex;gap:5px}
.typing-dots span{width:8px;height:8px;background:var(--g400);border-radius:50%;animation:dot 1.4s infinite}
.typing-dots span:nth-child(2){animation-delay:.2s}
.typing-dots span:nth-child(3){animation-delay:.4s}
@keyframes dot{0%,60%,100%{transform:translateY(0)}30%{transform:translateY(-6px)}}

/* Drag & Drop */
.drop-overlay{display:none;position:absolute;inset:0;background:rgba(37,99,235,.08);border:2px dashed var(--primary);z-index:50;align-items:center;justify-content:center;border-radius:var(--r);pointer-events:none}
.drop-overlay.active{display:flex}
.drop-content{text-align:center;color:var(--primary)}
.drop-content p{font-size:16px;font-weight:600;margin-top:8px}

/* Input */
.chat-input-area{padding:14px 20px;background:#fff;border-top:1px solid var(--g200);flex-shrink:0}
.file-bar{display:flex;align-items:center;justify-content:space-between;padding:8px 12px;background:var(--primary-bg);border-radius:var(--r-sm);margin-bottom:10px;font-size:13px;color:var(--primary);font-weight:500}
.btn-x{background:none;border:none;cursor:pointer;color:var(--g600);padding:2px;display:flex}
.input-row{display:flex;gap:10px;align-items:flex-end}
.btn-attach{cursor:pointer;padding:10px;display:flex;align-items:center;color:var(--g600);border-radius:var(--r-sm);transition:all var(--t)}
.btn-attach:hover{background:var(--g100);color:var(--primary)}
#chatInput{flex:1;padding:12px 16px;border:1.5px solid var(--g200);border-radius:var(--r);font-size:15px;resize:none;outline:none;max-height:120px;font-family:inherit;transition:border var(--t);line-height:1.5}
#chatInput:focus{border-color:var(--primary)}
.btn-send{width:48px;height:48px;background:var(--primary);color:#fff;border:none;border-radius:var(--r);cursor:pointer;display:flex;align-items:center;justify-content:center;transition:all var(--t);flex-shrink:0}
.btn-send:hover{background:var(--primary-d);transform:scale(1.05)}
.btn-send:disabled{background:var(--g400);cursor:not-allowed;transform:none}

/* PDF Panel */
.pdf-panel{width:48%;max-width:680px;background:#fff;border-left:1px solid var(--g200);display:flex;flex-direction:column;flex-shrink:0;box-shadow:-2px 0 12px rgba(0,0,0,.06);position:relative}
.pdf-resize-handle{position:absolute;left:-3px;top:0;bottom:0;width:6px;cursor:col-resize;z-index:10;background:transparent;transition:background var(--t)}
.pdf-resize-handle:hover{background:var(--primary);opacity:.3}
.pdf-header{display:flex;justify-content:space-between;align-items:center;padding:12px 16px;border-bottom:1px solid var(--g200);background:var(--g50);flex-shrink:0}
.pdf-title{font-weight:600;font-size:14px;color:var(--g900);overflow:hidden;text-overflow:ellipsis;white-space:nowrap;flex:1;margin-right:10px}
.pdf-actions{display:flex;gap:8px;align-items:center;flex-shrink:0}
.pdf-iframe{flex:1;border:none;width:100%}

/* Buttons */
.btn-primary{padding:14px 28px;background:var(--primary);color:#fff;border:none;border-radius:var(--r);font-size:16px;font-weight:600;cursor:pointer;transition:all var(--t)}
.btn-primary:hover{background:var(--primary-d);transform:translateY(-1px);box-shadow:var(--sh-md)}
.btn-large{padding:16px 40px;font-size:17px;border-radius:var(--r-lg)}
.btn-secondary{padding:14px 28px;background:var(--g100);color:var(--g900);border:1px solid var(--g200);border-radius:var(--r);font-size:16px;font-weight:600;cursor:pointer;transition:all var(--t)}
.btn-secondary:hover{background:var(--g200)}
.btn-sm{padding:8px 18px;font-size:14px}
.btn-outline{padding:8px 16px;background:transparent;color:var(--primary);border:1.5px solid var(--primary);border-radius:var(--r-sm);font-size:13px;font-weight:600;cursor:pointer;text-decoration:none;transition:all var(--t)}
.btn-outline:hover{background:var(--primary);color:#fff}
.btn-icon{width:36px;height:36px;background:transparent;border:none;border-radius:var(--r-sm);cursor:pointer;display:flex;align-items:center;justify-content:center;color:var(--g600);transition:all var(--t)}
.btn-icon:hover{background:var(--g100);color:var(--primary)}
.muted{color:var(--g400);font-size:13px}

/* Modal */
.modal-bg{position:fixed;inset:0;background:rgba(0,0,0,.4);backdrop-filter:blur(4px);display:flex;align-items:center;justify-content:center;z-index:1000}
.modal{background:#fff;border-radius:var(--r-lg);box-shadow:var(--sh-lg);padding:32px;width:440px;max-width:92vw;animation:modalUp .25s ease}
@keyframes modalUp{from{opacity:0;transform:translateY(12px)}to{opacity:1;transform:translateY(0)}}
.modal h3{color:var(--g900);margin-bottom:20px;font-size:20px}
.fg{display:flex;flex-direction:column;gap:4px}
.modal .fg{margin-bottom:14px}
.modal .fg label{font-size:13px;font-weight:600;color:var(--g700);display:block}
.modal input,.modal select{width:100%;padding:12px 14px;border:1.5px solid var(--g200);border-radius:var(--r-sm);font-size:15px;outline:none;transition:border var(--t)}
.modal input:focus,.modal select:focus{border-color:var(--primary)}
.modal-row{display:grid;grid-template-columns:1fr 1fr;gap:12px}
.modal-actions{display:flex;gap:10px;justify-content:flex-end;margin-top:24px}

/* Scrollbar */
::-webkit-scrollbar{width:6px}
::-webkit-scrollbar-track{background:transparent}
::-webkit-scrollbar-thumb{background:var(--g200);border-radius:3px}
.sidebar ::-webkit-scrollbar-thumb{background:var(--g700)}

/* Responsive */
@media(max-width:900px){
    .wf-side{display:none}
}
@media(max-width:768px){
    .sidebar{width:100%;position:fixed;z-index:100;height:100vh;transform:translateX(-100%);transition:transform .3s}
    .sidebar.open{transform:translateX(0)}
    .message{max-width:90%}
    .pdf-panel{width:100%;max-width:none;position:fixed;inset:0;z-index:200}
    .settings-bar{padding:8px 12px;gap:6px}
    .sb-group label{display:none}
    .modal-row{grid-template-columns:1fr}
}