:root{--primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);--secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);--success-gradient: linear-gradient(135deg, #43e97b 0%, #38f9d7 100%);--warning-gradient: linear-gradient(135deg, #fa709a 0%, #fee140 100%);--bg-light: #f5f7fa;--bg-gradient: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);--card-shadow: 0 4px 20px rgba(0, 0, 0, .08);--card-hover-shadow: 0 8px 30px rgba(0, 0, 0, .12);--radius: 12px;--radius-lg: 20px;--text-primary: #2d3748;--text-secondary: #718096;--border-color: #e2e8f0;--nav-height: 60px;--tab-height: 60px}*{margin:0;padding:0;box-sizing:border-box}body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,PingFang SC,Hiragino Sans GB,Microsoft YaHei,sans-serif;background:var(--bg-gradient);color:var(--text-primary);min-height:100vh}.app-container{max-width:1400px;margin:0 auto;padding:20px}.card{background:#fff;border-radius:var(--radius);box-shadow:var(--card-shadow);padding:24px;transition:box-shadow .3s ease}.card:hover{box-shadow:var(--card-hover-shadow)}.btn{padding:10px 24px;border:none;border-radius:8px;cursor:pointer;font-size:14px;font-weight:500;transition:all .3s ease;display:inline-flex;align-items:center;gap:6px}.btn-primary{background:var(--primary-gradient);color:#fff}.btn-primary:hover{transform:translateY(-2px);box-shadow:0 4px 15px #667eea66}.btn-success{background:var(--success-gradient);color:#fff}.btn-danger{background:var(--secondary-gradient);color:#fff}.btn-warning{background:var(--warning-gradient);color:#fff}.btn-sm{padding:6px 14px;font-size:12px}.btn:disabled{opacity:.6;cursor:not-allowed;transform:none!important}.input-group{margin-bottom:16px}.input-group label{display:block;margin-bottom:6px;font-weight:500;color:var(--text-secondary);font-size:14px}.input-group input,.input-group select,.input-group textarea{width:100%;padding:12px 16px;border:2px solid var(--border-color);border-radius:8px;font-size:14px;transition:border-color .3s ease;outline:none}.input-group input:focus,.input-group select:focus,.input-group textarea:focus{border-color:#667eea}.table-responsive{overflow-x:auto}table{width:100%;border-collapse:collapse}th,td{padding:12px 16px;text-align:left;border-bottom:1px solid var(--border-color)}th{background:#f7fafc;font-weight:600;color:var(--text-secondary);font-size:13px;text-transform:uppercase}tr:hover{background:#f7fafc}.modal-overlay{position:fixed;top:0;left:0;right:0;bottom:0;background:#00000080;display:flex;align-items:center;justify-content:center;z-index:1000;-webkit-backdrop-filter:blur(4px);backdrop-filter:blur(4px)}.modal{background:#fff;border-radius:var(--radius-lg);padding:32px;max-width:500px;width:90%;max-height:80vh;overflow-y:auto;box-shadow:0 20px 60px #0000004d}.modal h3{margin-bottom:20px;font-size:20px}.toast{position:fixed;top:20px;right:20px;padding:16px 24px;border-radius:8px;color:#fff;font-weight:500;z-index:2000;animation:slideIn .3s ease}.toast-success{background:var(--success-gradient)}.toast-error{background:var(--secondary-gradient)}@keyframes slideIn{0%{transform:translate(100%);opacity:0}to{transform:translate(0);opacity:1}}.empty-state{text-align:center;padding:60px 20px;color:var(--text-secondary)}.empty-state .icon{font-size:64px;margin-bottom:16px}.grid{display:grid;gap:20px}.grid-2{grid-template-columns:repeat(auto-fill,minmax(300px,1fr))}.grid-3{grid-template-columns:repeat(auto-fill,minmax(250px,1fr))}.grid-4{grid-template-columns:repeat(auto-fill,minmax(200px,1fr))}.tag{display:inline-block;padding:4px 12px;border-radius:20px;font-size:12px;font-weight:500}.tag-admin{background:linear-gradient(135deg,#667eea,#764ba2);color:#fff}.tag-teacher{background:linear-gradient(135deg,#43e97b,#38f9d7);color:#fff}.page-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:24px;flex-wrap:wrap;gap:12px}.page-header h2{font-size:24px;background:var(--primary-gradient);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}@media(max-width:768px){.app-container{padding:12px}.grid-2,.grid-3,.grid-4{grid-template-columns:1fr}.modal{width:95%;padding:20px}th,td{padding:8px 12px;font-size:13px}}