body { font-family: Arial, sans-serif; background: linear-gradient(135deg, #0f172a 0%, #111827 100%); color: #e5eefb; margin: 0; }
main { max-width: 1100px; margin: 32px auto; padding: 24px; }
.auth-card { max-width: 420px; margin: 120px auto; padding: 24px; background: #111827; border-radius: 16px; box-shadow: 0 10px 30px rgba(0,0,0,.25); }
.page-shell { display: flex; flex-direction: column; gap: 18px; }
.topbar, .grid, .panel, .card { background: #111827; border-radius: 16px; padding: 18px; box-shadow: 0 10px 30px rgba(0,0,0,.25); }
.topbar { display: flex; justify-content: space-between; align-items: flex-start; gap: 16px; flex-wrap: wrap; }
.topbar-main { display: flex; flex-direction: column; gap: 10px; }
.nav-links { display: flex; flex-wrap: wrap; gap: 8px; }
.nav-link { display: inline-flex; align-items: center; padding: 8px 12px; border-radius: 999px; background: #1f2937; color: #e5eefb; text-decoration: none; font-weight: 600; }
.nav-link:hover { background: #2563eb; }
.grid { display: grid; gap: 16px; }
.cards { grid-template-columns: repeat(4, 1fr); }
.two-col { grid-template-columns: 1.1fr 0.9fr; }
.card strong { display: block; font-size: 28px; margin-top: 8px; }
input, button, .btn { width: 100%; box-sizing: border-box; padding: 12px; margin-top: 8px; border-radius: 10px; border: 1px solid #334155; }
button, .btn { background: #2563eb; color: white; cursor: pointer; border: none; font-weight: 700; text-decoration: none; text-align: center; }
.btn-secondary { background: #475569; }
.error { color: #fecaca; font-size: 14px; }
table { width: 100%; border-collapse: collapse; }
th, td { text-align: left; padding: 10px; border-bottom: 1px solid #1f2937; }
.list-box { padding-left: 18px; line-height: 1.5; }
.tabs { display: flex; gap: 8px; }
.tab { padding: 10px 16px; border-radius: 10px; background: #1f2937; color: #e5eefb; text-decoration: none; font-weight: 700; }
.tab.is-active { background: #2563eb; }
.stack-form { display: grid; gap: 12px; max-width: 920px; }
.form-row, .filter-row { display: flex; gap: 12px; flex-wrap: wrap; align-items: end; }
.form-row label, .filter-row label { flex: 1; min-width: 180px; }
.notice { margin: 0; padding: 12px 14px; border-radius: 10px; background: #14532d; color: #dcfce7; }
.btn-danger { width: auto; margin: 0; padding: 8px 12px; background: #b91c1c; }
.workbook-layout { max-width: 1320px; min-height: 100vh; margin: 32px auto; padding: 24px; display: grid; grid-template-columns: 230px minmax(0, 1fr); gap: 24px; }
.workbook-sidebar { background: #111827; border-radius: 16px; padding: 22px 16px; box-shadow: 0 10px 30px rgba(0,0,0,.25); display: flex; flex-direction: column; gap: 22px; }
.workbook-sidebar h1 { font-size: 22px; margin: 0 0 8px; }
.workbook-sidebar p { margin: 0; color: #cbd5e1; font-size: 13px; line-height: 1.55; }
.sidebar-nav { display: grid; gap: 6px; }
.sidebar-nav a { padding: 11px 12px; border-radius: 9px; color: #dbeafe; font-weight: 700; text-decoration: none; }
.sidebar-nav a:hover, .sidebar-nav a.is-current { background: #2563eb; color: #fff; }
.sidebar-logout { margin-top: auto; }
.workbook-content { min-width: 0; display: flex; flex-direction: column; gap: 18px; }
.workbook-content .panel { margin: 0; }
.form-grid { display: grid; gap: 14px; }
.form-grid-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.form-grid-4 { grid-template-columns: minmax(260px, 2fr) repeat(3, minmax(140px, 1fr)); }
.form-grid label, .filter-grid label { display: grid; gap: 7px; color: #dbeafe; font-weight: 700; font-size: 14px; }
.form-grid input, .form-grid select, .filter-grid input, .filter-grid select { width: 100%; height: 44px; margin: 0; padding: 0 12px; border-radius: 9px; border: 1px solid #475569; background: #f8fafc; color: #0f172a; font: inherit; font-weight: 400; }
.form-grid select, .filter-grid select { appearance: auto; }
.filter-grid { display: grid; grid-template-columns: minmax(180px, 1fr) minmax(180px, 1fr) 120px; align-items: end; gap: 14px; margin: 0 0 18px; }
.filter-grid .btn { height: 44px; margin: 0; padding: 0 12px; }
.homework-filter-grid { display: grid; grid-template-columns: repeat(5, minmax(130px, 1fr)) 110px; gap: 14px; align-items: end; }
.homework-filter-grid label { display: grid; gap: 7px; color: #dbeafe; font-weight: 700; font-size: 14px; }
.homework-filter-grid input, .homework-filter-grid select { width: 100%; height: 44px; margin: 0; padding: 0 12px; border-radius: 9px; border: 1px solid #475569; background: #f8fafc; color: #0f172a; font: inherit; font-weight: 400; }
.homework-filter-grid .btn { height: 44px; margin: 0; padding: 0 12px; }
.homework-images { display: flex; flex-wrap: wrap; gap: 6px; }
.homework-images img { width: 72px; height: 72px; object-fit: cover; border-radius: 8px; border: 1px solid #334155; }
.section-heading { display: flex; justify-content: space-between; gap: 12px; align-items: baseline; margin-bottom: 16px; }
.section-heading h2 { margin: 0; }
.section-heading span { color: #94a3b8; font-size: 14px; }
.section-description { margin: -6px 0 18px; color: #cbd5e1; }
.table-wrap { overflow-x: auto; }
@media (max-width: 900px) { .workbook-layout { grid-template-columns: 1fr; padding: 16px; } .workbook-sidebar { gap: 16px; } .sidebar-nav { grid-template-columns: repeat(2, minmax(0, 1fr)); } .sidebar-logout { margin-top: 0; } .form-grid-3, .form-grid-4, .filter-grid, .homework-filter-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); } .filter-grid .btn, .homework-filter-grid .btn { grid-column: span 2; } }
@media (max-width: 560px) { .workbook-layout { padding: 12px; } .sidebar-nav, .form-grid-3, .form-grid-4, .filter-grid, .homework-filter-grid { grid-template-columns: 1fr; } .filter-grid .btn, .homework-filter-grid .btn { grid-column: auto; } }

/* Shared admin layout: the existing topbar becomes a left-side navigation. */
.page-shell { max-width: 1320px; display: grid; grid-template-columns: 230px minmax(0, 1fr); align-items: start; gap: 18px; }
.page-shell .topbar { grid-column: 1; grid-row: 1 / span 100; position: sticky; top: 24px; flex-direction: column; align-items: stretch; padding: 22px 16px; }
.page-shell .topbar-main { gap: 18px; }
.page-shell .topbar h1 { margin: 0 0 8px; font-size: 22px; }
.page-shell .topbar p { margin: 0; color: #cbd5e1; font-size: 13px; line-height: 1.55; }
.page-shell .nav-links { flex-direction: column; gap: 6px; }
.page-shell .nav-link { border-radius: 9px; }
.page-shell .topbar > .btn { margin-top: 10px; }
.page-shell .topbar > .btn-secondary, .sidebar-logout { display: none; }
@media (max-width: 900px) { .page-shell { display: flex; margin: 16px auto; padding: 16px; } .page-shell .topbar { position: static; } .page-shell .nav-links { flex-direction: row; } }