:root{--bg: #f4f7fb;--surface: #ffffff;--border: #dbe3ee;--text: #1f2d3d;--muted: #607086;--primary: #0f5ec9;--primary-2: #0a4ea8;--danger: #bf2f2f}*{box-sizing:border-box}body{margin:0;font-family:Segoe UI,Tahoma,Geneva,Verdana,sans-serif;background:radial-gradient(circle at top right,#e6eefc 0%,var(--bg) 60%);color:var(--text)}.app-shell{display:grid;grid-template-columns:260px 1fr;min-height:100vh}.sidebar{border-right:1px solid var(--border);background:#0d213f;color:#fff;padding:24px 16px}.brand h1{margin:0;font-size:1.4rem}.brand p{margin:6px 0 0;opacity:.85}.nav{margin-top:24px;display:flex;flex-direction:column;gap:8px}.nav-link{text-decoration:none;color:#d6e4ff;padding:10px 12px;border-radius:10px}.nav-link.active,.nav-link:hover{background:#ffffff26;color:#fff}.content{padding:20px}.topbar{display:flex;justify-content:space-between;align-items:center;gap:12px}.topbar h2{margin:0}.topbar p{margin:4px 0 0;color:var(--muted)}.content-body{margin-top:20px}.grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}.full{grid-column:1 / -1}.card{background:var(--surface);border:1px solid var(--border);border-radius:14px;padding:16px;box-shadow:0 10px 30px #101e360d}.btn{border:0;border-radius:10px;padding:10px 14px;cursor:pointer}.btn-primary{background:var(--primary);color:#fff}.btn-primary:hover{background:var(--primary-2)}.btn-secondary{background:#e5edf7;color:#113058}.field{display:grid;gap:6px;margin-bottom:12px}input,select{width:100%;border:1px solid var(--border);border-radius:10px;padding:10px 12px}.error{margin-bottom:12px;background:#ffe9e9;color:var(--danger);border:1px solid #ffcccc;padding:10px;border-radius:10px}.page-center{min-height:100vh;display:grid;place-items:center;padding:16px}.login-card{width:100%;max-width:420px}.students-screen{display:grid;gap:16px}.inline-form{display:flex;gap:10px}.form-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px;margin-bottom:14px}.table-wrap{overflow:auto}table{width:100%;border-collapse:collapse}th,td{border-bottom:1px solid var(--border);text-align:left;padding:10px 8px}.simple-list{margin:0;padding-left:18px}@media(max-width:992px){.app-shell{grid-template-columns:1fr}.sidebar{border-right:0;border-bottom:1px solid rgba(255,255,255,.2)}.grid,.form-grid{grid-template-columns:1fr}}