:root {
            --primary:#4f46e5;--primary-light:#6366f1;--primary-dark:#3730a3;
            --bg:#f0f2f5;--bg-card:#ffffff;--bg-sidebar:#ffffff;
            --text:#1e293b;--text-secondary:#64748b;--text-muted:#94a3b8;
            --border:#e4e7ed;--shadow:0 1px 3px rgba(0,0,0,.06),0 1px 2px rgba(0,0,0,.04);
            --shadow-lg:0 4px 12px rgba(0,0,0,.08);--shadow-xl:0 8px 24px rgba(0,0,0,.1);
            --radius:10px;--radius-sm:6px;--radius-lg:16px;
            --nav-height:56px;--transition:.2s ease;
            --success:#10b981;--danger:#ef4444;--warning:#f59e0b;
        }
        .dark{
            --bg:#0f172a;--bg-card:#1e293b;--bg-sidebar:#1e293b;
            --text:#e2e8f0;--text-secondary:#94a3b8;--text-muted:#64748b;
            --border:#334155;--shadow:0 1px 3px rgba(0,0,0,.3);--shadow-lg:0 4px 12px rgba(0,0,0,.4);--shadow-xl:0 8px 24px rgba(0,0,0,.5);
        }
        *{margin:0;padding:0;box-sizing:border-box;}
        body{
            font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"PingFang SC","Microsoft YaHei",sans-serif;
            background:var(--bg);color:var(--text);line-height:1.6;
            transition:background var(--transition),color var(--transition);min-height:100vh;
        }
        a{color:var(--primary);text-decoration:none;} a:hover{color:var(--primary-light);}
        ::-webkit-scrollbar{width:6px;}
        ::-webkit-scrollbar-track{background:transparent;}
        ::-webkit-scrollbar-thumb{background:var(--text-muted);border-radius:3px;}

        /* ===== Navbar ===== */
        .navbar{
            position:fixed;top:0;left:0;right:0;height:var(--nav-height);
            background:#fff;border-bottom:1px solid var(--border);
            display:flex;align-items:center;padding:0 32px;z-index:1000;
            box-shadow:0 1px 3px rgba(0,0,0,.04);
        }
        .dark .navbar{background:var(--bg-card);}
        .nav-logo{display:flex;align-items:center;gap:8px;font-size:1.15rem;font-weight:700;color:var(--primary);cursor:pointer;flex-shrink:0;}
        .nav-logo svg{width:26px;height:26px;}
        .nav-search{flex:1;max-width:400px;margin:0 24px;position:relative;}
        .nav-search input{
            width:100%;padding:8px 14px 8px 36px;border:1px solid var(--border);border-radius:8px;
            background:var(--bg);color:var(--text);font-size:.85rem;outline:none;transition:all var(--transition);
        }
        .nav-search input:focus{border-color:var(--primary);box-shadow:0 0 0 3px rgba(79,70,229,.1);}
        .nav-search svg{position:absolute;left:12px;top:50%;transform:translateY(-50%);color:var(--text-muted);width:16px;height:16px;}
        .nav-primary-menu{display:flex;align-items:center;gap:2px;margin:0 8px;flex-shrink:0;overflow-x:auto;scrollbar-width:none;}
        .nav-primary-menu::-webkit-scrollbar{display:none;}
        .nav-menu-item{padding:4px 10px;font-size:.82rem;color:var(--text-secondary);cursor:pointer;border-radius:6px;white-space:nowrap;transition:all var(--transition);position:relative;}
        .nav-menu-item:hover{background:var(--bg);color:var(--text);}
        .nav-menu-item.active{color:var(--primary);font-weight:600;background:rgba(79,70,229,.06);}
        .nav-menu-badge{background:var(--danger);color:#fff;font-size:.6rem;padding:1px 5px;border-radius:10px;position:absolute;top:-4px;right:-4px;min-width:14px;text-align:center;}
        .nav-secondary-menu{display:none;position:absolute;top:100%;left:0;background:var(--bg-card);border:1px solid var(--border);border-radius:8px;box-shadow:var(--shadow-xl);z-index:100;padding:6px 0;min-width:160px;}
        .nav-secondary-menu.show{display:block;}
        .nav-secondary-item{padding:8px 14px;font-size:.82rem;color:var(--text);cursor:pointer;white-space:nowrap;transition:background var(--transition);}
        .nav-secondary-item:hover{background:var(--bg);}
        .nav-actions{display:flex;align-items:center;gap:8px;margin-left:auto;flex-shrink:0;}
        .nav-btn{
            padding:7px 16px;border-radius:8px;border:1px solid var(--border);
            background:transparent;color:var(--text);cursor:pointer;font-size:.85rem;
            transition:all var(--transition);white-space:nowrap;
        }
        .nav-btn:hover{border-color:var(--primary);color:var(--primary);background:rgba(79,70,229,.04);}
        .nav-btn.primary{background:var(--primary);color:#fff;border-color:var(--primary);}
        .nav-btn.primary:hover{background:var(--primary-light);}
        .nav-btn.danger{color:var(--danger);border-color:transparent;}
        .nav-btn.danger:hover{background:rgba(239,68,68,.08);border-color:var(--danger);}
        .user-area{position:relative;display:flex;align-items:center;gap:8px;}
        .user-avatar{
            width:32px;height:32px;border-radius:50%;display:flex;align-items:center;justify-content:center;
            color:#fff;font-weight:600;font-size:.85rem;cursor:pointer;overflow:hidden;flex-shrink:0;
        }
        .user-dropdown{
            position:absolute;top:100%;right:0;margin-top:6px;background:var(--bg-card);
            border:1px solid var(--border);border-radius:10px;box-shadow:var(--shadow-xl);
            min-width:170px;padding:6px;display:none;z-index:1001;
        }
        .user-dropdown.open{display:block;}
        .user-dropdown-item{padding:9px 14px;border-radius:6px;cursor:pointer;font-size:.88rem;color:var(--text);transition:background var(--transition);}
        .user-dropdown-item:hover{background:var(--bg);}
        .user-dropdown-item.danger{color:var(--danger);}
        .user-dropdown-item.divider{border-top:1px solid var(--border);margin:4px 0;padding:0;cursor:default;}

        /* ===== Layout ===== */
        .app{display:flex;margin-top:var(--nav-height);min-height:calc(100vh - var(--nav-height));max-width:1400px;margin-left:auto;margin-right:auto;padding:20px 24px;gap:20px;}
        .sidebar{
            width:220px;flex-shrink:0;position:sticky;top:calc(var(--nav-height) + 20px);
            height:fit-content;max-height:calc(100vh - var(--nav-height) - 40px);overflow-y:auto;
            background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);
            padding:16px 12px;box-shadow:var(--shadow);
        }

        .sidebar-section{margin-bottom:12px;padding-bottom:12px;border-bottom:1px solid var(--border);}
        .sidebar-section:last-child{border-bottom:none;margin-bottom:0;padding-bottom:0;}
        .sidebar-title{font-size:.7rem;text-transform:uppercase;letter-spacing:.08em;color:var(--text-muted);font-weight:600;margin-bottom:4px;padding:0 8px;}
        .sidebar-item{
            display:flex;align-items:center;gap:8px;padding:8px 10px;border-radius:8px;
            cursor:pointer;color:var(--text-secondary);font-size:.88rem;transition:all var(--transition);font-weight:500;
        }
        .sidebar-item:hover{background:var(--bg);color:var(--text);}
        .sidebar-item.active{background:rgba(79,70,229,.08);color:var(--primary);font-weight:600;}
        .sidebar-item svg{width:16px;height:16px;flex-shrink:0;}

        .main{flex:1;min-width:0;}
        .rightbar{
            width:280px;flex-shrink:0;position:sticky;top:calc(var(--nav-height) + 20px);
            height:fit-content;max-height:calc(100vh - var(--nav-height) - 40px);overflow-y:auto;
            display:flex;flex-direction:column;gap:16px;
        }
        .rightbar-card{
            background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);
            padding:16px;box-shadow:var(--shadow);
        }
        .rightbar-title{font-size:.85rem;font-weight:600;margin-bottom:12px;color:var(--text);display:flex;align-items:center;gap:6px;}
        .rightbar-stats{display:grid;grid-template-columns:1fr 1fr;gap:10px;}
        .stat-item{text-align:center;padding:10px;border-radius:8px;background:var(--bg);}
        .stat-num{font-size:1.2rem;font-weight:700;color:var(--primary);}
        .stat-label{font-size:.75rem;color:var(--text-muted);margin-top:2px;}
        .hot-item{
            display:flex;gap:10px;padding:9px 0;border-bottom:1px solid var(--border);cursor:pointer;transition:all var(--transition);
        }
        .hot-item:last-child{border-bottom:none;padding-bottom:0;}
        .hot-item:hover .hot-title{color:var(--primary);}
        .hot-num{font-size:.9rem;font-weight:700;color:var(--text-muted);width:20px;text-align:center;flex-shrink:0;margin-top:2px;}
        .hot-num.top-1{color:#ef4444;} .hot-num.top-2{color:#f97316;} .hot-num.top-3{color:#eab308;}
        .hot-title{font-size:.82rem;transition:color var(--transition);display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden;}
        .hot-meta{font-size:.72rem;color:var(--text-muted);margin-top:2px;}

        /* ===== Section Header ===== */
        .section-header{
            display:flex;justify-content:space-between;align-items:center;
            margin-bottom:16px;padding-bottom:12px;border-bottom:2px solid var(--border);
        }
        .section-header h2{font-size:1.1rem;font-weight:700;}
        .section-header .more{font-size:.82rem;color:var(--text-muted);cursor:pointer;transition:color var(--transition);}
        .section-header .more:hover{color:var(--primary);}

        /* ===== Category Grid ===== */
        .category-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(200px,1fr));gap:12px;margin-bottom:28px;}
        .category-card{
            background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);
            padding:16px;cursor:pointer;transition:all var(--transition);box-shadow:var(--shadow);
        }
        .category-card:hover{transform:translateY(-2px);box-shadow:var(--shadow-lg);border-color:var(--primary);}
        .category-card .icon{font-size:1.6rem;margin-bottom:8px;}
        .category-card h3{font-size:.95rem;margin-bottom:2px;}
        .category-card p{color:var(--text-secondary);font-size:.8rem;}

        /* ===== Topic Grid ===== */
        .topic-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:12px;margin-bottom:16px;}
        .topic-item{
            background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);
            padding:18px;cursor:pointer;transition:all var(--transition);box-shadow:var(--shadow);
            display:flex;gap:14px;
        }
        .topic-item:hover{transform:translateY(-2px);box-shadow:var(--shadow-lg);border-color:var(--primary);}
        .topic-avatar{width:42px;height:42px;border-radius:50%;flex-shrink:0;overflow:hidden;}
        .topic-avatar img{width:100%;height:100%;object-fit:cover;}
        .topic-avatar .fallback{width:100%;height:100%;display:flex;align-items:center;justify-content:center;color:#fff;font-weight:600;font-size:.9rem;}
        .topic-content{flex:1;min-width:0;}
        .topic-tag{display:inline-block;padding:2px 8px;border-radius:4px;font-size:.7rem;font-weight:500;background:var(--bg);color:var(--text-secondary);margin-bottom:6px;}
        .topic-title{font-size:.93rem;font-weight:600;margin-bottom:4px;transition:color var(--transition);display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden;line-height:1.4;}
        .topic-item:hover .topic-title{color:var(--primary);}
        .topic-excerpt{color:var(--text-secondary);font-size:.8rem;display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden;margin-bottom:8px;line-height:1.5;}
        .topic-meta{display:flex;gap:12px;font-size:.75rem;color:var(--text-muted);flex-wrap:wrap;}
        .topic-meta span{display:flex;align-items:center;gap:3px;}
        .topic-actions{display:flex;align-items:center;gap:4px;margin-left:auto;flex-shrink:0;align-self:center;}
        .topic-like{display:flex;flex-direction:column;align-items:center;gap:1px;color:var(--text-muted);font-size:.75rem;cursor:pointer;padding:6px;border-radius:8px;transition:all var(--transition);}
        .topic-like:hover{background:var(--bg);}
        .topic-like svg{width:18px;height:18px;transition:color var(--transition);}
        .topic-like:hover svg{color:var(--danger);}
        .topic-like.liked svg{color:var(--danger);fill:var(--danger);}

        /* ===== Topic Detail ===== */
        .topic-detail-card{
            background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);
            padding:28px;box-shadow:var(--shadow);margin-bottom:20px;
        }
        .topic-detail-card h1{font-size:1.4rem;font-weight:700;margin-bottom:12px;}
        .topic-detail-meta{display:flex;gap:16px;align-items:center;flex-wrap:wrap;color:var(--text-secondary);font-size:.85rem;padding-bottom:16px;border-bottom:1px solid var(--border);margin-bottom:20px;}
        .topic-detail-meta .author{font-weight:600;color:var(--text);}
        .topic-detail-body{line-height:1.9;font-size:.95rem;color:var(--text);}
        .topic-detail-body img{max-width:100%;border-radius:8px;margin:12px 0;}
        .topic-detail-body p{margin-bottom:12px;}

        /* ===== Comments ===== */
        .comments-card{background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);padding:24px;box-shadow:var(--shadow);}
        .comments-title{font-size:1.05rem;font-weight:600;margin-bottom:16px;padding-bottom:12px;border-bottom:1px solid var(--border);}
        .comment{display:flex;gap:12px;padding:14px 0;border-bottom:1px solid var(--border);}
        .comment:last-child{border-bottom:none;}
        .comment-avatar{width:36px;height:36px;border-radius:50%;flex-shrink:0;overflow:hidden;}
        .comment-avatar img{width:100%;height:100%;object-fit:cover;}
        .comment-author-w{font-weight:600;font-size:.88rem;margin-bottom:3px;display:flex;align-items:center;gap:8px;flex-wrap:wrap;}
        .comment-time{font-size:.72rem;color:var(--text-muted);font-weight:400;}
        .comment-reply-btn{font-size:.75rem;color:var(--primary);cursor:pointer;opacity:0;transition:opacity var(--transition);}
        .comment:hover .comment-reply-btn{opacity:1;}
        .reply-indicator{display:none;padding:8px 14px;background:var(--bg);border-radius:8px;font-size:.82rem;color:var(--text-secondary);margin-bottom:8px;align-items:center;gap:8px;}
        .reply-indicator.show{display:flex;}
        .reply-indicator .cancel{color:var(--danger);cursor:pointer;font-size:.78rem;margin-left:auto;}
        .comment-text{color:var(--text-secondary);font-size:.88rem;line-height:1.6;}
        .comment-form{margin-top:16px;display:flex;gap:10px;align-items:flex-start;}
        .comment-form textarea{flex:1;padding:10px 14px;border:1px solid var(--border);border-radius:8px;background:var(--bg);color:var(--text);font-size:.88rem;resize:vertical;min-height:70px;outline:none;font-family:inherit;transition:border var(--transition);}
        .comment-form textarea:focus{border-color:var(--primary);}
        .comment-form-right{display:flex;flex-direction:column;gap:6px;flex-shrink:0;}
        .comment-form button{padding:10px 20px;border:none;border-radius:8px;background:var(--primary);color:#fff;cursor:pointer;font-size:.85rem;transition:background var(--transition);white-space:nowrap;}
        .comment-form button:hover{background:var(--primary-light);}
        .comment-toolbar{display:flex;gap:4px;}
        .comment-toolbar .editor-btn{padding:6px 10px;border:1px solid var(--border);border-radius:6px;background:var(--bg-card);color:var(--text);cursor:pointer;font-size:.85rem;line-height:1;transition:all var(--transition);}
        .comment-toolbar .editor-btn:hover{border-color:var(--primary);}
        .comment-replies{margin-left:48px;padding-left:16px;border-left:2px solid var(--border);margin-top:8px;}

        /* ===== Pagination ===== */
        .pagination{display:flex;justify-content:center;gap:6px;margin-top:16px;}
        .page-btn{
            padding:7px 13px;border:1px solid var(--border);border-radius:8px;
            background:var(--bg-card);color:var(--text);cursor:pointer;font-size:.82rem;transition:all var(--transition);
        }
        .page-btn:hover{border-color:var(--primary);color:var(--primary);}
        .page-btn.active{background:var(--primary);color:#fff;border-color:var(--primary);}
        .page-btn:disabled{opacity:.4;cursor:default;}

        /* ===== Back Button ===== */
        .back-btn{
            display:inline-flex;align-items:center;gap:5px;padding:6px 12px;border-radius:8px;
            border:1px solid var(--border);background:var(--bg-card);color:var(--text-secondary);
            cursor:pointer;font-size:.82rem;margin-bottom:16px;transition:all var(--transition);
        }
        .back-btn:hover{border-color:var(--primary);color:var(--primary);}

        /* ===== Modals ===== */
        .modal-overlay{
            display:none;position:fixed;inset:0;background:rgba(0,0,0,.5);
            backdrop-filter:blur(4px);z-index:2000;align-items:center;justify-content:center;padding:20px;
        }
        .modal-overlay.active{display:flex;}
        .modal{
            background:var(--bg-card);border-radius:var(--radius-lg);width:100%;max-width:460px;
            max-height:90vh;overflow-y:auto;padding:28px;box-shadow:var(--shadow-xl);
        }
        .modal h2{font-size:1.2rem;font-weight:700;margin-bottom:20px;}
        .form-group{margin-bottom:14px;}
        .form-group label{display:block;font-size:.82rem;font-weight:500;margin-bottom:5px;color:var(--text-secondary);}
        .form-group input,.form-group select,.form-group textarea{
            width:100%;padding:9px 12px;border:1px solid var(--border);border-radius:8px;
            background:var(--bg);color:var(--text);font-size:.88rem;outline:none;transition:border var(--transition);font-family:inherit;
        }
        .form-group input:focus,.form-group select:focus,.form-group textarea:focus{border-color:var(--primary);}
        .form-group textarea{min-height:110px;resize:vertical;}
        .form-actions{display:flex;gap:10px;justify-content:flex-end;margin-top:18px;}
        .form-actions button{padding:9px 22px;border-radius:8px;border:none;cursor:pointer;font-size:.88rem;transition:all var(--transition);}
        .form-actions .cancel{background:var(--bg);color:var(--text);}
        .form-actions .cancel:hover{background:var(--border);}
        .form-actions .submit{background:var(--primary);color:#fff;}
        .form-actions .submit:hover{background:var(--primary-light);}
        .form-actions .submit:disabled{opacity:.5;cursor:default;}
        .form-error{font-size:.8rem;color:var(--danger);margin-top:4px;}
        .auth-switch{text-align:center;margin-top:14px;font-size:.88rem;color:var(--text-secondary);}
        .auth-switch a{color:var(--primary);cursor:pointer;font-weight:500;}
        .auth-switch a:hover{text-decoration:underline;}
        .send-code-btn{padding:8px 12px;border:1px solid var(--border);border-radius:8px;background:var(--bg);color:var(--text);cursor:pointer;font-size:.8rem;white-space:nowrap;transition:all var(--transition);}
        .send-code-btn:hover{border-color:var(--primary);color:var(--primary);}
        .send-code-btn:disabled{opacity:.4;cursor:default;}
        .code-row{display:flex;gap:8px;}

        /* Chat Page */
        .chat-page{display:flex;gap:0;background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);overflow:hidden;box-shadow:var(--shadow);min-height:65vh;}
        .chat-sidebar{width:300px;flex-shrink:0;border-right:1px solid var(--border);display:flex;flex-direction:column;}
        .chat-sidebar h3{padding:16px;font-size:.95rem;font-weight:600;border-bottom:1px solid var(--border);}
        .chat-sidebar-list{flex:1;overflow-y:auto;}
        .chat-main{flex:1;display:flex;flex-direction:column;min-width:0;}
        .chat-main-header{padding:14px 20px;border-bottom:1px solid var(--border);display:flex;align-items:center;gap:10px;font-weight:600;font-size:.95rem;}
        .chat-main-header .back{display:none;}
        .chat-main-body{flex:1;overflow-y:auto;padding:16px 20px;background:var(--bg);}
        .chat-main-input{padding:10px 16px;border-top:1px solid var(--border);display:flex;gap:8px;align-items:center;background:var(--bg-card);}
        .chat-main-input textarea{flex:1;padding:10px 16px;border:1px solid var(--border);border-radius:22px;background:var(--bg);color:var(--text);font-size:.88rem;resize:none;outline:none;font-family:inherit;height:44px;line-height:1.4;transition:border var(--transition);}
        .chat-main-input textarea:focus{border-color:var(--primary);}
        .chat-main-input button{width:44px;height:44px;border:none;border-radius:50%;background:var(--primary);color:#fff;cursor:pointer;font-size:.85rem;transition:all var(--transition);display:flex;align-items:center;justify-content:center;flex-shrink:0;}
        .chat-main-input button:hover{background:var(--primary-light);transform:scale(1.05);}
        .chat-main-input button svg{width:20px;height:20px;}

        .chat-msg{display:flex;gap:10px;margin-bottom:14px;padding:0;}
        .chat-msg.mine{flex-direction:row-reverse;}
        .chat-msg-avatar{width:32px;height:32px;border-radius:50%;flex-shrink:0;overflow:hidden;}
        .chat-msg-bubble{max-width:70%;padding:10px 16px;border-radius:16px;font-size:.88rem;line-height:1.5;word-break:break-word;}
        .chat-msg.mine .chat-msg-bubble{background:var(--primary);color:#fff;border-bottom-right-radius:4px;}
        .chat-msg:not(.mine) .chat-msg-bubble{background:#fff;color:var(--text);border-bottom-left-radius:4px;box-shadow:0 1px 2px rgba(0,0,0,.06);}
        .dark .chat-msg:not(.mine) .chat-msg-bubble{background:var(--bg-card);}

        .conv-item{padding:14px 16px;cursor:pointer;display:flex;align-items:center;gap:10px;transition:background var(--transition);border-bottom:1px solid var(--border);}
        .conv-item:last-child{border-bottom:none;}
        .conv-item:hover,.conv-item.active{background:var(--bg);}
        .conv-item .info{flex:1;min-width:0;}
        .conv-item .name{font-size:.88rem;font-weight:500;display:flex;align-items:center;gap:6px;}
        .conv-item .preview{font-size:.78rem;color:var(--text-muted);overflow:hidden;text-overflow:ellipsis;white-space:nowrap;margin-top:2px;}
        .conv-item .time{font-size:.7rem;color:var(--text-muted);flex-shrink:0;}
        .conv-item .unread-badge{background:var(--danger);color:#fff;font-size:.65rem;padding:2px 6px;border-radius:10px;min-width:18px;text-align:center;}

        .nav-chat-btn{position:relative;padding:6px 10px;border:none;background:transparent;cursor:pointer;border-radius:8px;transition:background var(--transition);}
        .nav-chat-btn:hover{background:var(--bg);}
        .nav-chat-btn svg{width:20px;height:20px;color:var(--text-secondary);}
        .nav-chat-badge{position:absolute;top:-2px;right:-2px;background:var(--danger);color:#fff;font-size:.65rem;padding:1px 5px;border-radius:10px;min-width:16px;text-align:center;display:none;}

        .chat-empty{text-align:center;padding:80px 20px;color:var(--text-muted);font-size:.9rem;}
        .chat-empty svg{width:48px;height:48px;margin-bottom:12px;opacity:.4;}

        @media(max-width:768px){
            .chat-sidebar{width:100%;}
            .chat-main{width:100%;display:none;}
            .chat-main.show{display:flex;}
            .chat-sidebar.hide{display:none;}
            .chat-main-header .back{display:inline-flex;align-items:center;gap:4px;cursor:pointer;color:var(--primary);font-size:.82rem;border:none;background:none;padding:4px 8px;}
            .chat-main-body{padding:12px;}
            .chat-msg-bubble{max-width:85%;font-size:.85rem;padding:8px 14px;}
        }
        .cat-picker{display:flex;flex-wrap:wrap;gap:8px;}
        .cat-option{padding:8px 14px;border:1px solid var(--border);border-radius:8px;cursor:pointer;display:flex;align-items:center;gap:8px;font-size:.85rem;transition:all var(--transition);background:var(--bg);}
        .cat-option:hover{border-color:var(--primary);}
        .cat-option.selected{border-color:var(--primary);background:rgba(79,70,229,.08);color:var(--primary);font-weight:600;}
        .cat-option img{width:22px;height:22px;border-radius:4px;object-fit:cover;}
        .editor-toolbar{display:flex;gap:6px;margin-bottom:6px;}
        .editor-btn{padding:6px 12px;border:1px solid var(--border);border-radius:6px;background:var(--bg-card);color:var(--text);cursor:pointer;font-size:.8rem;transition:all var(--transition);}
        .editor-btn:hover{border-color:var(--primary);color:var(--primary);}
        .upload-preview{display:flex;gap:8px;flex-wrap:wrap;margin-top:8px;}
        .upload-preview img{width:80px;height:80px;object-fit:cover;border-radius:6px;border:1px solid var(--border);}
        .code-row input{flex:1;}
        .login-tabs{display:flex;gap:0;margin-bottom:16px;border-bottom:2px solid var(--border);}
        .login-tab{padding:9px 18px;cursor:pointer;font-size:.88rem;color:var(--text-secondary);border-bottom:2px solid transparent;margin-bottom:-2px;transition:all var(--transition);}
        .login-tab.active{color:var(--primary);border-bottom-color:var(--primary);font-weight:600;}

        /* ===== Toast ===== */
        .toast{
            position:fixed;bottom:24px;left:50%;transform:translateX(-50%) translateY(80px);
            background:var(--bg-card);border:1px solid var(--border);border-radius:10px;
            padding:12px 24px;box-shadow:var(--shadow-xl);z-index:3000;
            opacity:0;transition:all .3s ease;font-size:.9rem;
        }
        .toast.show{opacity:1;transform:translateX(-50%) translateY(0);}

        /* ===== Empty & Loading ===== */
        .empty-state{text-align:center;padding:60px 20px;color:var(--text-muted);}
        .empty-state svg{width:56px;height:56px;margin-bottom:14px;opacity:.4;}
        .empty-state h3{font-size:1rem;margin-bottom:6px;color:var(--text-secondary);}
        .loading-state{text-align:center;padding:60px;}
        .spinner{width:28px;height:28px;border:3px solid var(--border);border-top-color:var(--primary);border-radius:50%;animation:spin .8s linear infinite;margin:0 auto 12px;}
        @keyframes spin{to{transform:rotate(360deg)}}

        /* ===== Mobile ===== */
        .mobile-toggle{display:none;background:none;border:none;color:var(--text);cursor:pointer;padding:4px;margin-right:4px;}
        .mobile-toggle svg{width:22px;height:22px;}
        .sidebar-overlay{display:none;}

        @media(max-width:1024px){
            .rightbar{display:none;}
            .app{padding:16px;}
        }
        @media(max-width:768px){
            .sidebar{position:fixed;left:-240px;top:var(--nav-height);width:240px;height:calc(100vh - var(--nav-height));z-index:999;transition:left .3s ease;border-radius:0;box-shadow:var(--shadow-xl);}
            .sidebar.open{left:0;}
            .sidebar-overlay{display:none;position:fixed;inset:0;background:rgba(0,0,0,.3);z-index:998;}
            .sidebar-overlay.open{display:block;}
            .mobile-toggle{display:block;}
            .nav-primary-menu{display:none;}
            .app{padding:12px;gap:0;}
            .navbar{padding:0 12px;}
            .nav-search{max-width:120px;margin:0 8px;}
            .nav-search input{padding:6px 10px 6px 28px;font-size:.78rem;}
            .nav-search svg{left:9px;width:14px;height:14px;}
            .nav-btn{padding:5px 10px;font-size:.78rem;}
            .nav-logo span{display:none;}
            .topic-grid{grid-template-columns:1fr;}
            .category-grid{grid-template-columns:repeat(auto-fill,minmax(140px,1fr));}
            .topic-detail-card{padding:16px;}
            .comments-card{padding:16px;}
            .topic-like{display:none;}
            .comment-form{flex-direction:column;gap:6px;}
            .comment-replies{margin-left:0;padding-left:12px;}
            .comment-form textarea{min-height:50px;}
            .comment-form-right{flex-direction:row;align-items:stretch;gap:6px;}
            .comment-form-right button{flex:1;}
            .comment-toolbar{flex:1;}
            .comment-toolbar .editor-btn{flex:1;text-align:center;padding:8px 10px;}
            .modal{padding:20px 16px;border-radius:var(--radius-lg) var(--radius-lg) 0 0;max-height:85vh;}
            .modal-overlay{align-items:flex-end;}
        }