*, *::before, *::after { margin:0; padding:0; box-sizing:border-box; }
:root {
  --bg: #f5f5f7;
  --white: #fff;
  --sidebar: #1a1a2e;
  --sidebar-hover: #16213e;
  --primary: #4f46e5;
  --primary-light: #eef2ff;
  --success: #059669;
  --success-light: #ecfdf5;
  --warning: #d97706;
  --warning-light: #fffbeb;
  --danger: #dc2626;
  --danger-light: #fef2f2;
  --info: #2563eb;
  --info-light: #eff6ff;
  --text: #1f2937;
  --text-secondary: #6b7280;
  --text-muted: #9ca3af;
  --border: #e5e7eb;
  --radius: 8px;
  --radius-lg: 12px;
  --shadow: 0 1px 3px rgba(0,0,0,.08);
}
body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif; background:var(--bg); color:var(--text); font-size:14px; line-height:1.5; }

#app { display:flex; min-height:100vh; }
#sidebar { width:200px; background:var(--sidebar); color:#e5e7eb; display:flex; flex-direction:column; flex-shrink:0; }
.logo { display:flex; align-items:center; gap:10px; padding:18px 16px; border-bottom:1px solid rgba(255,255,255,.1); }
.logo-icon { width:36px; height:36px; border-radius:8px; background:var(--primary); color:#fff; display:flex; align-items:center; justify-content:center; font-weight:700; font-size:14px; }
.logo-title { font-size:15px; font-weight:600; color:#fff; }
.logo-sub { font-size:11px; color:#9ca3af; }
#nav { flex:1; padding:8px 0; }
.nav-item { display:flex; align-items:center; gap:10px; padding:10px 16px; color:#9ca3af; text-decoration:none; font-size:13px; transition:all .15s; border-left:3px solid transparent; }
.nav-item:hover { color:#e5e7eb; background:rgba(255,255,255,.05); }
.nav-item.active { color:#fff; background:rgba(79,70,229,.2); border-left-color:var(--primary); }
.nav-icon { font-size:10px; }
.nav-divider { height:1px; background:rgba(255,255,255,.1); margin:8px 16px; }
#user-info { padding:12px 16px; border-top:1px solid rgba(255,255,255,.1); display:flex; align-items:center; justify-content:space-between; font-size:12px; }
#logout-btn { background:none; border:1px solid rgba(255,255,255,.2); color:#9ca3af; padding:4px 10px; border-radius:4px; cursor:pointer; font-size:11px; }
#logout-btn:hover { color:#fff; border-color:#fff; }

#main { flex:1; display:flex; flex-direction:column; overflow-y:auto; }
#topbar { padding:16px 24px; border-bottom:1px solid var(--border); background:var(--white); }
#page-title { font-size:18px; font-weight:600; }
#content { flex:1; padding:24px; }

/* Metric cards */
.metrics { display:grid; grid-template-columns:repeat(auto-fit, minmax(150px, 1fr)); gap:14px; margin-bottom:24px; }
.metric-card { background:var(--white); border-radius:var(--radius-lg); padding:18px; border:1px solid var(--border); box-shadow:var(--shadow); }
.metric-label { font-size:12px; color:var(--text-secondary); margin-bottom:6px; }
.metric-value { font-size:26px; font-weight:700; }
.metric-value.blue { color:var(--info); }
.metric-value.green { color:var(--success); }
.metric-value.red { color:var(--danger); }
.metric-value.amber { color:var(--warning); }

/* Panel */
.panel { background:var(--white); border-radius:var(--radius-lg); border:1px solid var(--border); box-shadow:var(--shadow); margin-bottom:24px; }
.panel-header { padding:14px 18px; border-bottom:1px solid var(--border); display:flex; align-items:center; justify-content:space-between; }
.panel-title { font-size:15px; font-weight:600; }
.panel-body { padding:18px; }

/* Table */
table { width:100%; border-collapse:collapse; }
th, td { padding:10px 14px; text-align:left; border-bottom:1px solid var(--border); font-size:13px; }
th { background:var(--bg); color:var(--text-secondary); font-weight:600; font-size:12px; text-transform:uppercase; letter-spacing:.5px; }
tr:hover td { background:#fafafa; }
.badge { display:inline-block; padding:2px 8px; border-radius:12px; font-size:11px; font-weight:600; }
.badge-green { background:var(--success-light); color:var(--success); }
.badge-red { background:var(--danger-light); color:var(--danger); }
.badge-amber { background:var(--warning-light); color:var(--warning); }
.badge-blue { background:var(--info-light); color:var(--info); }

/* Buttons */
.btn { display:inline-flex; align-items:center; gap:6px; padding:7px 14px; border-radius:var(--radius); font-size:13px; font-weight:500; cursor:pointer; border:1px solid var(--border); background:var(--white); color:var(--text); transition:all .15s; }
.btn:hover { background:var(--bg); }
.btn-primary { background:var(--primary); color:#fff; border-color:var(--primary); }
.btn-primary:hover { background:#4338ca; }
.btn-danger { background:var(--danger); color:#fff; border-color:var(--danger); }
.btn-danger:hover { background:#b91c1c; }
.btn-sm { padding:4px 10px; font-size:12px; }
.btn-group { display:flex; gap:8px; }

/* Forms */
input, select, textarea { width:100%; padding:8px 12px; border:1px solid var(--border); border-radius:var(--radius); font-size:13px; font-family:inherit; transition:border-color .15s; }
input:focus, select:focus, textarea:focus { outline:none; border-color:var(--primary); box-shadow:0 0 0 3px rgba(79,70,229,.1); }
.form-group { margin-bottom:14px; }
.form-label { display:block; font-size:12px; font-weight:600; color:var(--text-secondary); margin-bottom:4px; }
.form-row { display:grid; grid-template-columns:1fr 1fr; gap:12px; }

/* Modal */
.overlay { position:fixed; inset:0; background:rgba(0,0,0,.4); display:flex; align-items:center; justify-content:center; z-index:100; }
.modal-box { background:var(--white); border-radius:var(--radius-lg); width:90%; max-width:560px; max-height:80vh; overflow-y:auto; padding:24px; box-shadow:0 8px 30px rgba(0,0,0,.15); }
.modal-title { font-size:16px; font-weight:600; margin-bottom:18px; }
.modal-actions { display:flex; justify-content:flex-end; gap:8px; margin-top:20px; padding-top:16px; border-top:1px solid var(--border); }

.login-card { background:var(--white); border-radius:var(--radius-lg); padding:36px; width:90%; max-width:380px; text-align:center; box-shadow:0 8px 30px rgba(0,0,0,.15); }
.login-card h1 { font-size:22px; margin-bottom:4px; }
.login-sub { color:var(--text-secondary); font-size:13px; margin-bottom:24px; }
.login-card input { margin-bottom:12px; padding:10px 14px; }
.login-card button { width:100%; padding:10px; border:none; border-radius:var(--radius); background:var(--primary); color:#fff; font-size:14px; font-weight:600; cursor:pointer; }
.login-card button:hover { background:#4338ca; }
.error-text { color:var(--danger); font-size:12px; margin-top:8px; }

/* Schedule Grid */
.schedule-tabs { display:flex; gap:0; margin-bottom:16px; }
.schedule-tab { padding:8px 20px; border:1px solid var(--border); background:var(--white); cursor:pointer; font-size:13px; font-weight:500; }
.schedule-tab:first-child { border-radius:var(--radius) 0 0 var(--radius); }
.schedule-tab:last-child { border-radius:0 var(--radius) var(--radius) 0; border-left:none; }
.schedule-tab.active { background:var(--primary); color:#fff; border-color:var(--primary); }
.schedule-grid { overflow-x:auto; }
.schedule-grid table { min-width:800px; }
.schedule-grid th { position:sticky; top:0; z-index:1; text-align:center; min-width:100px; }
.schedule-grid td { text-align:center; padding:6px; font-size:11px; vertical-align:top; min-height:36px; }
.schedule-cell { padding:4px 6px; border-radius:4px; font-size:11px; line-height:1.4; cursor:pointer; transition: all .15s; }
.schedule-cell:hover { opacity:.8; }
.schedule-cell .s-name { font-weight:600; font-size:12px; }
.schedule-cell .s-info { font-size:10px; color:inherit; opacity:.7; }
.time-label { font-size:10px; color:var(--text-muted); white-space:nowrap; padding:4px 6px; }

/* Attendance */
.att-list { display:flex; flex-direction:column; gap:8px; }
.att-item { display:flex; align-items:center; gap:12px; padding:12px 14px; background:var(--white); border-radius:var(--radius); border:1px solid var(--border); }
.att-time { font-weight:600; font-size:15px; min-width:80px; }
.att-student { flex:1; }
.att-name { font-weight:600; }
.att-course { font-size:12px; color:var(--text-secondary); }
.att-status { padding:4px 12px; border-radius:var(--radius); font-size:12px; font-weight:600; }
.att-status.present { background:var(--success-light); color:var(--success); }
.att-status.absent { background:var(--danger-light); color:var(--danger); }
.att-status.leave { background:var(--warning-light); color:var(--warning); }
.att-actions { display:flex; gap:6px; }

/* Loading & Empty */
.loading { text-align:center; padding:40px; color:var(--text-muted); }
.empty { text-align:center; padding:40px; color:var(--text-muted); font-size:13px; }
.empty-icon { font-size:36px; margin-bottom:8px; opacity:.3; }

/* Utility */
.flex-between { display:flex; align-items:center; justify-content:space-between; }
.gap-sm { gap:8px; }
.mb-sm { margin-bottom:12px; }
.mb-md { margin-bottom:20px; }
.text-sm { font-size:12px; }
.text-muted { color:var(--text-secondary); }