/* Light theme (default) */
:root {
    --bg:#f0f2f5;--bg2:#ffffff;--bg3:#f5f6fa;--bg4:#e8eaf0;
    --accent:#5f4dd0;--accent2:#6c5ce7;--accent-glow:rgba(108,92,231,.08);
    --success:#00a884;--warning:#e6a817;--danger:#d63031;--info:#0984e3;
    --text:#1a1d27;--text2:#4a4e69;--text3:#8b8fa3;
    --border:#dfe1e8;--radius:12px;--shadow:0 4px 24px rgba(0,0,0,.08);
    --font:'Inter',sans-serif;
    --logo-gradient-end:#1a1d27;
    --modal-backdrop:rgba(0,0,0,.35);
}

/* Dark theme override */
[data-theme="dark"] {
    --bg:#0f1117;--bg2:#1a1d27;--bg3:#242836;--bg4:#2e3345;
    --accent:#6c5ce7;--accent2:#a29bfe;--accent-glow:rgba(108,92,231,.15);
    --success:#00b894;--warning:#fdcb6e;--danger:#e17055;--info:#74b9ff;
    --text:#e8e8f0;--text2:#a0a3b5;--text3:#6b6f82;
    --border:#2e3345;--shadow:0 4px 24px rgba(0,0,0,.3);
    --logo-gradient-end:#fff;
    --modal-backdrop:rgba(0,0,0,.6);
}

/* Theme toggle button */
.theme-toggle{background:none;border:1px solid var(--border);color:var(--text2);cursor:pointer;padding:7px 9px;border-radius:8px;font-size:16px;transition:.2s;display:flex;align-items:center;justify-content:center}
.theme-toggle:hover{border-color:var(--accent);color:var(--accent2);background:var(--accent-glow)}
/* Light mode: show moon icon (click to go dark) */
.theme-toggle .fa-sun{display:none !important}
.theme-toggle .fa-moon{display:inline-block !important}
/* Dark mode: show sun icon (click to go light) */
[data-theme="dark"] .theme-toggle .fa-sun{display:inline-block !important}
[data-theme="dark"] .theme-toggle .fa-moon{display:none !important}

*{margin:0;padding:0;box-sizing:border-box}
body{font-family:var(--font);background:var(--bg);color:var(--text);line-height:1.6;min-height:100vh;transition:background .3s,color .3s}
a{color:var(--accent2);text-decoration:none;transition:.2s}
a:hover{color:var(--accent)}
.app-layout{display:flex;min-height:100vh}
.sidebar{width:260px;background:var(--bg2);border-right:1px solid var(--border);display:flex;flex-direction:column;position:fixed;height:100vh;z-index:100;transition:.3s}
.sidebar.collapsed{width:70px}
.sidebar-header{padding:20px;display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid var(--border)}
.logo{display:flex;align-items:center;gap:10px}
.logo-icon{width:38px;height:38px;background:linear-gradient(135deg,var(--accent),var(--accent2));border-radius:10px;display:flex;align-items:center;justify-content:center;color:#fff;font-size:18px}
.logo-text{font-weight:700;font-size:18px;background:linear-gradient(135deg,var(--accent2),var(--logo-gradient-end));-webkit-background-clip:text;-webkit-text-fill-color:transparent}
.sidebar-toggle{background:none;border:none;color:var(--text2);cursor:pointer;font-size:16px;padding:6px}
.sidebar-nav{flex:1;overflow-y:auto;padding:12px 0}
.sidebar-nav ul{list-style:none}
.nav-section-title{padding:12px 20px 6px;font-size:11px;text-transform:uppercase;letter-spacing:1.5px;color:var(--text3);font-weight:600}
.nav-link{display:flex;align-items:center;gap:12px;padding:10px 20px;color:var(--text2);font-size:14px;font-weight:500;transition:.2s;border-left:3px solid transparent}
.nav-link:hover{background:var(--accent-glow);color:var(--accent2);border-left-color:var(--accent)}
.nav-link.active{background:var(--accent-glow);color:var(--accent2);border-left-color:var(--accent)}
.nav-link i{width:20px;text-align:center;font-size:15px}
.sidebar-footer{padding:16px;border-top:1px solid var(--border)}
.user-card{display:flex;align-items:center;gap:10px;padding:8px;border-radius:var(--radius);background:var(--bg3)}
.user-avatar{width:36px;height:36px;border-radius:10px;background:linear-gradient(135deg,var(--accent),var(--accent2));display:flex;align-items:center;justify-content:center;color:#fff;font-weight:700;font-size:14px;flex-shrink:0}
.user-avatar-sm{width:30px;height:30px;border-radius:8px;background:linear-gradient(135deg,var(--accent),var(--accent2));display:flex;align-items:center;justify-content:center;color:#fff;font-weight:600;font-size:12px}
.user-info{flex:1;min-width:0}
.user-name{display:block;font-size:13px;font-weight:600;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.user-role{display:block;font-size:11px;color:var(--text3)}
.logout-btn{color:var(--text3);font-size:14px;padding:4px}
.logout-btn:hover{color:var(--danger)}
.main-content{flex:1;margin-left:260px;min-height:100vh;transition:.3s}
.top-bar{display:flex;align-items:center;gap:16px;padding:16px 28px;border-bottom:1px solid var(--border);background:var(--bg2);position:sticky;top:0;z-index:50;backdrop-filter:blur(12px)}
.mobile-menu-btn{display:none;background:none;border:none;color:var(--text);font-size:20px;cursor:pointer}
.search-bar{flex:1;display:flex;align-items:center;gap:10px;background:var(--bg3);border-radius:10px;padding:8px 16px;max-width:420px}
.search-bar i{color:var(--text3);font-size:14px}
.search-bar input{background:none;border:none;color:var(--text);font-size:14px;width:100%;outline:none;font-family:var(--font)}
.top-bar-actions{display:flex;align-items:center;gap:12px;margin-left:auto}
.notification-btn{background:none;border:none;color:var(--text2);font-size:18px;cursor:pointer;position:relative;padding:6px}
.notif-badge{position:absolute;top:0;right:0;background:var(--danger);color:#fff;font-size:10px;padding:1px 5px;border-radius:10px;font-weight:700}
.user-dropdown{position:relative}
.user-dropdown-btn{display:flex;align-items:center;gap:8px;background:none;border:none;color:var(--text);cursor:pointer;padding:4px 8px;border-radius:8px;font-family:var(--font);font-size:13px;font-weight:500}
.user-dropdown-btn:hover{background:var(--bg3)}
.dropdown-menu{position:absolute;top:100%;right:0;background:var(--bg2);border:1px solid var(--border);border-radius:var(--radius);padding:6px;min-width:180px;display:none;box-shadow:var(--shadow);margin-top:8px;z-index:200}
.dropdown-menu.show{display:block}
.dropdown-menu a{display:flex;align-items:center;gap:10px;padding:10px 14px;color:var(--text2);font-size:13px;border-radius:8px;transition:.15s}
.dropdown-menu a:hover{background:var(--accent-glow);color:var(--accent2)}
.content-area{padding:28px}
.page-header{margin-bottom:28px}
.page-header h1{font-size:26px;font-weight:700;margin-bottom:4px}
.page-header p{color:var(--text2);font-size:14px}
.stats-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:20px;margin-bottom:28px}
.stat-card{background:var(--bg2);border:1px solid var(--border);border-radius:var(--radius);padding:22px;display:flex;align-items:center;gap:16px;transition:.2s}
.stat-card:hover{border-color:var(--accent);transform:translateY(-2px);box-shadow:var(--shadow)}
.stat-icon{width:50px;height:50px;border-radius:12px;display:flex;align-items:center;justify-content:center;font-size:22px}
.stat-icon.purple{background:rgba(108,92,231,.15);color:var(--accent2)}
.stat-icon.green{background:rgba(0,184,148,.15);color:var(--success)}
.stat-icon.orange{background:rgba(253,203,110,.15);color:var(--warning)}
.stat-icon.blue{background:rgba(116,185,255,.15);color:var(--info)}
.stat-info h3{font-size:26px;font-weight:700}
.stat-info p{color:var(--text2);font-size:13px}
.card{background:var(--bg2);border:1px solid var(--border);border-radius:var(--radius);overflow:hidden;transition:.2s}
.card:hover{border-color:var(--accent)}
.card-header{padding:18px 22px;border-bottom:1px solid var(--border);display:flex;align-items:center;justify-content:space-between}
.card-header h2{font-size:17px;font-weight:600}
.card-body{padding:22px}
.card-footer{padding:14px 22px;border-top:1px solid var(--border);display:flex;justify-content:flex-end}
.grid-2{display:grid;grid-template-columns:repeat(auto-fit,minmax(360px,1fr));gap:20px;margin-bottom:20px}
.grid-3{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:20px;margin-bottom:20px}
.btn{display:inline-flex;align-items:center;gap:8px;padding:10px 20px;border-radius:10px;font-size:14px;font-weight:600;cursor:pointer;border:none;font-family:var(--font);transition:.2s}
.btn-primary{background:linear-gradient(135deg,var(--accent),var(--accent2));color:#fff}
.btn-primary:hover{opacity:.9;transform:translateY(-1px);box-shadow:0 4px 16px rgba(108,92,231,.4);color:#fff}
.btn-success{background:var(--success);color:#fff}
.btn-danger{background:var(--danger);color:#fff}
.btn-outline{background:none;border:1px solid var(--border);color:var(--text2)}
.btn-outline:hover{border-color:var(--accent);color:var(--accent2)}
.btn-sm{padding:6px 14px;font-size:12px;border-radius:8px}
.btn-lg{padding:14px 28px;font-size:16px}
.form-group{margin-bottom:18px}
.form-group label{display:block;font-size:13px;font-weight:600;margin-bottom:6px;color:var(--text2)}
.form-control{width:100%;padding:10px 14px;background:var(--bg3);border:1px solid var(--border);border-radius:10px;color:var(--text);font-size:14px;font-family:var(--font);transition:.2s;outline:none}
.form-control:focus{border-color:var(--accent);box-shadow:0 0 0 3px var(--accent-glow)}
textarea.form-control{min-height:100px;resize:vertical}
select.form-control{appearance:none;background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%23a0a3b5' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10z'/%3E%3C/svg%3E");background-repeat:no-repeat;background-position:right 12px center}
.form-row{display:grid;grid-template-columns:1fr 1fr;gap:16px}
.table-wrapper{overflow-x:auto}
table{width:100%;border-collapse:collapse}
table th,table td{padding:12px 16px;text-align:left;border-bottom:1px solid var(--border);font-size:14px}
table th{font-weight:600;color:var(--text2);font-size:12px;text-transform:uppercase;letter-spacing:.5px;background:var(--bg3)}
table tr:hover td{background:var(--accent-glow)}
.badge{display:inline-flex;align-items:center;padding:3px 10px;border-radius:20px;font-size:11px;font-weight:600}
.badge-success{background:rgba(0,184,148,.15);color:var(--success)}
.badge-warning{background:rgba(253,203,110,.15);color:var(--warning)}
.badge-danger{background:rgba(225,112,85,.15);color:var(--danger)}
.badge-info{background:rgba(116,185,255,.15);color:var(--info)}
.badge-purple{background:rgba(108,92,231,.15);color:var(--accent2)}
.alert{display:flex;align-items:center;gap:12px;padding:14px 18px;border-radius:var(--radius);margin-bottom:20px;font-size:14px;animation:slideDown .3s ease}
.alert-success{background:rgba(0,184,148,.1);border:1px solid rgba(0,184,148,.3);color:var(--success)}
.alert-error{background:rgba(225,112,85,.1);border:1px solid rgba(225,112,85,.3);color:var(--danger)}
.alert-info{background:rgba(116,185,255,.1);border:1px solid rgba(116,185,255,.3);color:var(--info)}
.alert-floating{position:fixed;top:20px;right:20px;z-index:9999;min-width:300px}
.alert-close{background:none;border:none;color:inherit;cursor:pointer;margin-left:auto;opacity:.7}
.modal-overlay{position:fixed;inset:0;background:var(--modal-backdrop);display:none;align-items:center;justify-content:center;z-index:1000;backdrop-filter:blur(4px)}
.modal-overlay.show{display:flex}
.modal{background:var(--bg2);border:1px solid var(--border);border-radius:16px;width:90%;max-width:600px;max-height:85vh;overflow-y:auto;box-shadow:var(--shadow)}
.modal-header{padding:20px 24px;border-bottom:1px solid var(--border);display:flex;align-items:center;justify-content:space-between}
.modal-header h2{font-size:18px}
.modal-close{background:none;border:none;color:var(--text3);font-size:20px;cursor:pointer}
.modal-body{padding:24px}
.modal-footer{padding:16px 24px;border-top:1px solid var(--border);display:flex;justify-content:flex-end;gap:10px}
.empty-state{text-align:center;padding:60px 20px;color:var(--text3)}
.empty-state i{font-size:48px;margin-bottom:16px;opacity:.3}
.empty-state h3{font-size:18px;margin-bottom:8px;color:var(--text2)}
.class-card{background:var(--bg2);border:1px solid var(--border);border-radius:var(--radius);overflow:hidden;transition:.3s}
.class-card:hover{transform:translateY(-4px);box-shadow:var(--shadow);border-color:var(--accent)}
.class-card-cover{height:140px;background:linear-gradient(135deg,var(--accent),#4834d4);display:flex;align-items:center;justify-content:center;position:relative}
.class-card-cover i{font-size:40px;color:rgba(255,255,255,.3)}
.class-card-code{position:absolute;top:12px;right:12px;background:rgba(0,0,0,.4);padding:4px 10px;border-radius:6px;font-size:11px;font-weight:600;color:#fff;backdrop-filter:blur(4px)}
.class-card-body{padding:18px}
.class-card-body h3{font-size:16px;font-weight:600;margin-bottom:6px}
.class-card-body p{color:var(--text2);font-size:13px;display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical;overflow:hidden}
.class-card-footer{padding:12px 18px;border-top:1px solid var(--border);display:flex;align-items:center;justify-content:space-between;font-size:12px;color:var(--text3)}
.material-item{display:flex;align-items:flex-start;gap:14px;padding:16px;border:1px solid var(--border);border-radius:var(--radius);margin-bottom:12px;transition:.2s;background:var(--bg2)}
.material-item:hover{border-color:var(--accent)}
.material-icon{width:44px;height:44px;border-radius:10px;display:flex;align-items:center;justify-content:center;font-size:18px;flex-shrink:0}
.material-info{flex:1}
.material-info h4{font-size:15px;font-weight:600;margin-bottom:3px}
.material-info p{font-size:13px;color:var(--text2)}
.file-item{display:flex;align-items:center;gap:10px;padding:10px 14px;border:1px solid var(--border);border-radius:8px;margin-top:8px;font-size:13px;background:var(--bg3)}
.file-item i{color:var(--accent2)}
.file-item span{flex:1}
.file-item .file-size{color:var(--text3);font-size:11px}
.eval-card{background:var(--bg2);border:1px solid var(--border);border-radius:var(--radius);padding:20px;margin-bottom:14px;transition:.2s}
.eval-card:hover{border-color:var(--accent)}
.eval-header{display:flex;align-items:center;justify-content:space-between;margin-bottom:10px}
.eval-type{font-size:11px;text-transform:uppercase;letter-spacing:1px;font-weight:700}
.eval-meta{display:flex;gap:16px;font-size:13px;color:var(--text2);margin-top:8px}
.eval-meta i{margin-right:4px}
.question-block{background:var(--bg3);border:1px solid var(--border);border-radius:var(--radius);padding:20px;margin-bottom:16px}
.question-number{display:inline-flex;align-items:center;justify-content:center;width:28px;height:28px;border-radius:8px;background:var(--accent);color:#fff;font-size:12px;font-weight:700;margin-right:10px}
.question-text{font-size:15px;margin-bottom:14px;line-height:1.7}
.question-type-badge{font-size:10px;padding:2px 8px;border-radius:4px;text-transform:uppercase;font-weight:700;letter-spacing:.5px}
.scaffolding-step{border-left:3px solid var(--accent);padding:16px 20px;margin:12px 0;background:var(--bg2);border-radius:0 var(--radius) var(--radius) 0}
.scaffolding-step.completed{border-left-color:var(--success)}
.scaffolding-step.locked{opacity:.5;border-left-color:var(--text3)}
.step-header{display:flex;align-items:center;gap:8px;margin-bottom:8px;font-weight:600;font-size:14px}
.step-status{width:24px;height:24px;border-radius:50%;display:flex;align-items:center;justify-content:center;font-size:11px}
.step-status.done{background:var(--success);color:#fff}
.step-status.current{background:var(--accent);color:#fff;animation:pulse 2s infinite}
.step-status.locked{background:var(--bg4);color:var(--text3)}
.guidance-box{background:rgba(108,92,231,.1);border:1px solid rgba(108,92,231,.3);border-radius:10px;padding:14px 18px;margin-top:10px;font-size:13px;color:var(--accent2)}
.guidance-box.correct{background:rgba(0,184,148,.1);border-color:rgba(0,184,148,.3);color:var(--success)}
.guidance-box.incorrect{background:rgba(225,112,85,.1);border-color:rgba(225,112,85,.3);color:var(--danger)}
.forum-post{background:var(--bg2);border:1px solid var(--border);border-radius:var(--radius);padding:20px;margin-bottom:14px;transition:.2s}
.forum-post:hover{border-color:var(--accent)}
.forum-post-header{display:flex;align-items:center;gap:12px;margin-bottom:12px}
.forum-post-meta{flex:1}
.forum-post-meta h3{font-size:16px;font-weight:600}
.forum-post-meta span{font-size:12px;color:var(--text3)}
.forum-post-content{font-size:14px;color:var(--text2);line-height:1.7;margin-bottom:14px}
.forum-actions{display:flex;gap:16px;font-size:13px;color:var(--text3)}
.forum-actions button{background:none;border:none;color:var(--text3);cursor:pointer;display:flex;align-items:center;gap:5px;font-size:13px;font-family:var(--font);transition:.2s}
.forum-actions button:hover{color:var(--accent2)}
.forum-actions button.liked{color:var(--danger)}
.reply-item{padding:14px 0;border-bottom:1px solid var(--border);margin-left:20px}
.reply-item:last-child{border-bottom:none}
.grade-cell{font-weight:700;font-size:16px}
.grade-a{color:var(--success)}
.grade-b{color:var(--info)}
.grade-c{color:var(--warning)}
.grade-d{color:var(--danger)}
.progress-bar{height:8px;background:var(--bg4);border-radius:4px;overflow:hidden}
.progress-fill{height:100%;border-radius:4px;background:linear-gradient(90deg,var(--accent),var(--accent2));transition:width .5s ease}
.tabs{display:flex;gap:4px;border-bottom:1px solid var(--border);margin-bottom:20px}
.tab-btn{padding:10px 20px;background:none;border:none;color:var(--text3);font-size:14px;font-weight:500;cursor:pointer;border-bottom:2px solid transparent;font-family:var(--font);transition:.2s}
.tab-btn.active{color:var(--accent2);border-bottom-color:var(--accent)}
.tab-btn:hover{color:var(--text)}
.tab-content{display:none}
.tab-content.active{display:block}
.login-page{min-height:100vh;display:flex;align-items:center;justify-content:center;background:var(--bg);position:relative;overflow:hidden}
.login-bg{position:absolute;inset:0;background:radial-gradient(circle at 30% 50%,rgba(108,92,231,.08),transparent 50%),radial-gradient(circle at 70% 80%,rgba(162,155,254,.06),transparent 50%)}
.login-card{background:var(--bg2);border:1px solid var(--border);border-radius:20px;padding:40px;width:420px;max-width:90%;position:relative;box-shadow:var(--shadow)}
.login-logo{text-align:center;margin-bottom:30px}
.login-logo .logo-icon{width:56px;height:56px;font-size:24px;margin:0 auto 12px}
.login-logo h1{font-size:24px;font-weight:700;background:linear-gradient(135deg,var(--accent2),var(--logo-gradient-end));-webkit-background-clip:text;-webkit-text-fill-color:transparent}
.login-logo p{color:var(--text3);font-size:13px;margin-top:4px}
.login-card .form-group{margin-bottom:16px}
.login-card .btn{width:100%;justify-content:center;padding:12px}
.login-footer{text-align:center;margin-top:20px;font-size:13px;color:var(--text3)}
.login-footer a{color:var(--accent2)}
.login-theme-toggle{position:absolute;top:20px;right:20px}
.pagination{display:flex;gap:6px;justify-content:center;margin-top:20px}
.pagination a,.pagination span{padding:8px 14px;border-radius:8px;font-size:13px;font-weight:500}
.pagination a{background:var(--bg3);color:var(--text2);border:1px solid var(--border)}
.pagination a:hover{border-color:var(--accent);color:var(--accent2)}
.pagination span.current{background:var(--accent);color:#fff}
@keyframes slideDown{from{opacity:0;transform:translateY(-10px)}to{opacity:1;transform:translateY(0)}}
@keyframes pulse{0%,100%{box-shadow:0 0 0 0 rgba(108,92,231,.4)}50%{box-shadow:0 0 0 8px rgba(108,92,231,0)}}
@media(max-width:768px){
.sidebar{transform:translateX(-100%);position:fixed}
.sidebar.open{transform:translateX(0)}
.main-content{margin-left:0}
.mobile-menu-btn{display:block}
.form-row{grid-template-columns:1fr}
.stats-grid{grid-template-columns:1fr}
.grid-2,.grid-3{grid-template-columns:1fr}
.top-bar{padding:12px 16px}
.content-area{padding:16px}
}