:root {
  --bg: #f4f6fa; --card: #ffffff; --ink: #1f2937; --muted: #6b7280;
  --line: #e5e7eb; --accent: #2563eb; --accent-dark: #1e46a8;
  --ok: #047857; --err: #b91c1c; --warn: #b45309;
}
* { box-sizing: border-box; }
body {
  margin: 0; background: var(--bg); color: var(--ink);
  font: 15px/1.5 -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
}
nav {
  display: flex; align-items: center; gap: 18px; flex-wrap: wrap;
  background: #111827; padding: 10px 24px;
}
nav a { color: #d1d5db; text-decoration: none; padding: 4px 2px; }
nav a.on, nav a:hover { color: #ffffff; border-bottom: 2px solid var(--accent); }
nav .brand { color: #fff; font-weight: 700; margin-right: 12px; }
nav .spacer { flex: 1; }
nav .who { color: #9ca3af; font-size: 13px; }
main { max-width: 1200px; margin: 24px auto; padding: 0 20px; }

h1 { font-size: 22px; margin: 0 0 12px; }
h2 { font-size: 17px; margin: 4px 0 12px; }
.page-head { display: flex; align-items: center; gap: 14px; flex-wrap: wrap; margin-bottom: 16px; }
.page-head h1 { margin: 0; }

.card {
  background: var(--card); border: 1px solid var(--line); border-radius: 12px;
  padding: 20px; margin-bottom: 20px; box-shadow: 0 1px 2px rgba(0,0,0,.04);
}
.login-card { max-width: 420px; margin: 8vh auto; }

table { width: 100%; border-collapse: collapse; }
th, td { padding: 8px 10px; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }
th { font-size: 13px; color: var(--muted); font-weight: 600; white-space: nowrap; }
td.num { text-align: right; white-space: nowrap; font-variant-numeric: tabular-nums; }
td.neg { color: var(--err); font-weight: 600; }
td.pos { color: var(--ok); }
tr.total-row td { border-top: 2px solid var(--ink); }
td.actions { white-space: nowrap; text-align: right; }

form label { display: block; margin-bottom: 12px; font-size: 14px; }
form input:not([type=checkbox]), form select {
  display: block; width: 100%; margin-top: 4px; padding: 8px 10px;
  border: 1px solid var(--line); border-radius: 8px; font: inherit; background: #fff;
}
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0 16px; }
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
@media (max-width: 900px) { .grid-3, .grid-2 { grid-template-columns: 1fr; } }
.form-actions { display: flex; align-items: center; gap: 12px; margin-top: 8px; }
.inline-form { display: flex; gap: 8px; align-items: end; margin: 0; }
.inline-form input { margin-top: 0; width: auto; }

button, .btn {
  display: inline-block; padding: 8px 14px; border: 1px solid var(--line);
  border-radius: 8px; background: #fff; color: var(--ink); font: inherit;
  cursor: pointer; text-decoration: none;
}
button.primary, .btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
button.primary:hover, .btn.primary:hover { background: var(--accent-dark); }
button.danger { color: var(--err); border-color: var(--err); }
button.small, .btn.small { padding: 3px 9px; font-size: 13px; }
.btn.ghost { background: transparent; }
.btn:hover { border-color: var(--muted); }

.flash { padding: 10px 14px; border-radius: 8px; margin-bottom: 14px; }
.flash.ok { background: #ecfdf5; color: var(--ok); border: 1px solid #a7f3d0; }
.flash.error { background: #fef2f2; color: var(--err); border: 1px solid #fecaca; }
.flash.warn { background: #fffbeb; color: var(--warn); border: 1px solid #fde68a; }

.muted { color: var(--muted); font-size: 13px; }
.students-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 6px 14px; margin: 10px 0 16px; }
@media (max-width: 900px) { .students-grid { grid-template-columns: repeat(2, 1fr); } }
.check-item { display: flex; align-items: center; gap: 8px; font-size: 14px; }
.check-item input { width: auto; }
.receipt-text { white-space: pre-wrap; font-family: inherit; margin: 0; }