* { margin: 0; padding: 0; box-sizing: border-box; }

:root {
    --primary: #1a73e8;
    --primary-dark: #1557b0;
    --primary-light: #e8f0fe;
    --success: #0d904f;
    --success-light: #e6f4ea;
    --danger: #d93025;
    --danger-light: #fce8e6;
    --warning: #f9ab00;
    --warning-light: #fef7e0;
    --gray-50: #f8f9fa;
    --gray-100: #f1f3f4;
    --gray-200: #e8eaed;
    --gray-300: #dadce0;
    --gray-500: #9aa0a6;
    --gray-700: #5f6368;
    --gray-900: #202124;
    --white: #ffffff;
    --shadow: 0 1px 3px rgba(0,0,0,0.12), 0 1px 2px rgba(0,0,0,0.08);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.1), 0 2px 4px rgba(0,0,0,0.06);
    --shadow-lg: 0 10px 25px rgba(0,0,0,0.1), 0 6px 10px rgba(0,0,0,0.08);
    --radius: 8px;
    --radius-lg: 12px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--gray-100);
    color: var(--gray-900);
    line-height: 1.5;
    min-height: 100vh;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ============ LOGIN PAGE ============ */
.login-page {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    background: linear-gradient(135deg, var(--primary) 0%, #0d47a1 100%);
    padding: 20px;
}

.login-box {
    background: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    padding: 40px;
    width: 100%;
    max-width: 400px;
}

.login-box h1 {
    text-align: center;
    color: var(--primary);
    margin-bottom: 8px;
    font-size: 24px;
}

.login-box .subtitle {
    text-align: center;
    color: var(--gray-700);
    margin-bottom: 30px;
    font-size: 14px;
}

/* ============ FORM ELEMENTS ============ */
.form-group {
    margin-bottom: 16px;
}

.form-group label {
    display: block;
    margin-bottom: 6px;
    font-weight: 600;
    font-size: 14px;
    color: var(--gray-700);
}

.form-control {
    width: 100%;
    padding: 12px 14px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius);
    font-size: 15px;
    transition: border-color 0.2s, box-shadow 0.2s;
    background: var(--white);
}

.form-control:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(26,115,232,0.15);
}

select.form-control {
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%235f6368' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10l-5 5z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    padding-right: 36px;
}

textarea.form-control {
    resize: vertical;
    min-height: 80px;
}

/* ============ BUTTONS ============ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    padding: 10px 20px;
    border: none;
    border-radius: var(--radius);
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    text-decoration: none;
    white-space: nowrap;
}

.btn:hover { text-decoration: none; opacity: 0.9; }
.btn:disabled { opacity: 0.6; cursor: not-allowed; }

.btn-primary { background: var(--primary); color: var(--white); }
.btn-primary:hover { background: var(--primary-dark); }

.btn-success { background: var(--success); color: var(--white); }
.btn-success:hover { background: #0a7340; }

.btn-danger { background: var(--danger); color: var(--white); }
.btn-danger:hover { background: #b71c1c; }

.btn-warning { background: var(--warning); color: var(--gray-900); }

.btn-outline {
    background: transparent;
    border: 1px solid var(--gray-300);
    color: var(--gray-700);
}
.btn-outline:hover { background: var(--gray-50); }

.btn-sm { padding: 6px 12px; font-size: 13px; }
.btn-lg { padding: 14px 28px; font-size: 16px; }

.btn-block { width: 100%; }

/* ============ LAYOUT ============ */
.sidebar {
    position: fixed;
    left: 0; top: 0; bottom: 0;
    width: 260px;
    background: var(--white);
    border-right: 1px solid var(--gray-200);
    z-index: 100;
    overflow-y: auto;
    transition: transform 0.3s;
}

.sidebar-header {
    padding: 20px;
    border-bottom: 1px solid var(--gray-200);
}

.sidebar-header h2 {
    font-size: 18px;
    color: var(--primary);
}

.sidebar-header p {
    font-size: 12px;
    color: var(--gray-500);
}

.sidebar-menu {
    list-style: none;
    padding: 10px 0;
}

.sidebar-menu li a {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 20px;
    color: var(--gray-700);
    font-size: 14px;
    transition: all 0.2s;
}

.sidebar-menu li a:hover,
.sidebar-menu li a.active {
    background: var(--primary-light);
    color: var(--primary);
    text-decoration: none;
}

.sidebar-menu .menu-divider {
    height: 1px;
    background: var(--gray-200);
    margin: 8px 20px;
}

.sidebar-menu .menu-label {
    padding: 8px 20px 4px;
    font-size: 11px;
    font-weight: 700;
    text-transform: uppercase;
    color: var(--gray-500);
    letter-spacing: 0.5px;
}

.main-content {
    margin-left: 260px;
    min-height: 100vh;
}

.topbar {
    background: var(--white);
    border-bottom: 1px solid var(--gray-200);
    padding: 12px 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: sticky;
    top: 0;
    z-index: 50;
}

.topbar h3 {
    font-size: 18px;
    color: var(--gray-900);
}

.topbar-user {
    display: flex;
    align-items: center;
    gap: 12px;
}

.topbar-user span {
    font-size: 14px;
    color: var(--gray-700);
}

.content {
    padding: 24px;
}

/* ============ CARDS ============ */
.card {
    background: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    overflow: hidden;
}

.card-header {
    padding: 16px 20px;
    border-bottom: 1px solid var(--gray-200);
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 10px;
}

.card-header h3 {
    font-size: 16px;
    color: var(--gray-900);
}

.card-body {
    padding: 20px;
}

/* ============ STAT CARDS ============ */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 16px;
    margin-bottom: 24px;
}

.stat-card {
    background: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow);
    padding: 20px;
    display: flex;
    align-items: center;
    gap: 16px;
}

.stat-icon {
    width: 48px;
    height: 48px;
    border-radius: var(--radius);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 22px;
}

.stat-icon.blue { background: var(--primary-light); color: var(--primary); }
.stat-icon.green { background: var(--success-light); color: var(--success); }
.stat-icon.red { background: var(--danger-light); color: var(--danger); }
.stat-icon.yellow { background: var(--warning-light); color: var(--warning); }

.stat-info h4 {
    font-size: 24px;
    color: var(--gray-900);
}

.stat-info p {
    font-size: 13px;
    color: var(--gray-500);
}

/* ============ TABLE ============ */
.table-responsive {
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
}

table th,
table td {
    padding: 10px 14px;
    text-align: left;
    border-bottom: 1px solid var(--gray-200);
    font-size: 14px;
}

table th {
    background: var(--gray-50);
    font-weight: 600;
    color: var(--gray-700);
    white-space: nowrap;
}

table tr:hover { background: var(--gray-50); }

.badge {
    display: inline-block;
    padding: 3px 10px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 600;
}

.badge-success { background: var(--success-light); color: var(--success); }
.badge-danger { background: var(--danger-light); color: var(--danger); }
.badge-warning { background: var(--warning-light); color: var(--warning); }
.badge-info { background: var(--primary-light); color: var(--primary); }

/* ============ MODAL ============ */
.modal-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.5);
    z-index: 200;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.modal-overlay.active { display: flex; }

.modal {
    background: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    width: 100%;
    max-width: 500px;
    max-height: 90vh;
    overflow-y: auto;
}

.modal-header {
    padding: 16px 20px;
    border-bottom: 1px solid var(--gray-200);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.modal-header h3 { font-size: 16px; }

.modal-close {
    background: none;
    border: none;
    font-size: 24px;
    cursor: pointer;
    color: var(--gray-500);
    padding: 0;
    line-height: 1;
}

.modal-body { padding: 20px; }

.modal-footer {
    padding: 12px 20px;
    border-top: 1px solid var(--gray-200);
    display: flex;
    justify-content: flex-end;
    gap: 8px;
}

/* ============ ALERTS ============ */
.alert {
    padding: 12px 16px;
    border-radius: var(--radius);
    margin-bottom: 16px;
    font-size: 14px;
}

.alert-success { background: var(--success-light); color: var(--success); }
.alert-danger { background: var(--danger-light); color: var(--danger); }
.alert-warning { background: var(--warning-light); color: #8a6d00; }

/* ============ GRADE INPUT PAGE ============ */
.grade-input-container {
    max-width: 700px;
    margin: 0 auto;
}

.grade-input-card {
    background: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    padding: 30px;
    text-align: center;
}

.grade-meta {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin-bottom: 8px;
    flex-wrap: wrap;
}

.grade-meta span {
    font-size: 14px;
    color: var(--gray-700);
    font-weight: 500;
}

.student-counter {
    font-size: 14px;
    color: var(--gray-500);
    margin-bottom: 20px;
}

.student-name {
    font-size: 36px;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 30px;
    min-height: 50px;
}

.grade-input-wrapper {
    margin-bottom: 30px;
}

.grade-input {
    width: 200px;
    height: 80px;
    text-align: center;
    font-size: 42px;
    font-weight: 700;
    border: 3px solid var(--gray-300);
    border-radius: var(--radius-lg);
    color: var(--gray-900);
    background: var(--white);
    transition: all 0.2s;
}

.grade-input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 4px rgba(26,115,232,0.15);
}

.grade-input.saved {
    border-color: var(--success);
    background: var(--success-light);
}

.nav-buttons {
    display: flex;
    justify-content: center;
    gap: 16px;
    margin-bottom: 20px;
}

.nav-buttons .btn {
    padding: 16px 40px;
    font-size: 18px;
    font-weight: 700;
    min-width: 160px;
}

.progress-bar-container {
    background: var(--gray-200);
    border-radius: 20px;
    height: 10px;
    overflow: hidden;
    margin-bottom: 10px;
}

.progress-bar {
    height: 100%;
    background: var(--primary);
    border-radius: 20px;
    transition: width 0.3s;
}

.progress-text {
    font-size: 13px;
    color: var(--gray-500);
}

.grade-status {
    margin-top: 15px;
    font-size: 14px;
    font-weight: 600;
}

.grade-status.saved { color: var(--success); }
.grade-status.unsaved { color: var(--gray-500); }

/* ============ QUICK NAV GRID ============ */
.student-nav-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(42px, 1fr));
    gap: 4px;
    margin-top: 15px;
    max-height: 200px;
    overflow-y: auto;
    padding: 5px;
}

.student-nav-btn {
    width: 42px;
    height: 36px;
    border: 1px solid var(--gray-300);
    border-radius: 4px;
    background: var(--white);
    font-size: 12px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.15s;
}

.student-nav-btn:hover { border-color: var(--primary); }
.student-nav-btn.active { background: var(--primary); color: var(--white); border-color: var(--primary); }
.student-nav-btn.done { background: var(--success-light); color: var(--success); border-color: var(--success); }

/* ============ FILTER BAR ============ */
.filter-bar {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
    align-items: flex-end;
    margin-bottom: 20px;
}

.filter-bar .form-group { margin-bottom: 0; min-width: 150px; }

/* ============ TOGGLE SIDEBAR ============ */
.menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 24px;
    cursor: pointer;
    color: var(--gray-700);
    padding: 4px;
}

/* ============ RESPONSIVE ============ */
@media (max-width: 768px) {
    .sidebar {
        transform: translateX(-100%);
    }
    .sidebar.open { transform: translateX(0); }

    .main-content { margin-left: 0; }

    .menu-toggle { display: block; }

    .content { padding: 16px; }

    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 10px;
    }

    .stat-card { padding: 14px; }
    .stat-info h4 { font-size: 20px; }

    .student-name { font-size: 26px; }
    .grade-input { width: 160px; height: 64px; font-size: 32px; }
    .nav-buttons .btn { padding: 14px 24px; font-size: 16px; min-width: 120px; }

    .filter-bar { flex-direction: column; }
    .filter-bar .form-group { min-width: 100%; }

    .topbar h3 { font-size: 15px; }

    table { font-size: 13px; }
    table th, table td { padding: 8px 10px; }
}

@media (max-width: 480px) {
    .stats-grid { grid-template-columns: 1fr; }
    .login-box { padding: 24px; }
    .grade-input-card { padding: 20px; }
    .grade-input { width: 140px; height: 56px; font-size: 28px; }
    .nav-buttons { flex-direction: column; }
    .nav-buttons .btn { min-width: 100%; }
}

/* ============ PRINT ============ */
@media print {
    .sidebar, .topbar, .no-print { display: none !important; }
    .main-content { margin-left: 0; }
    .content { padding: 0; }
    .card { box-shadow: none; border: 1px solid #ddd; }
    body { background: white; font-size: 12px; }
    table { font-size: 11px; }
}

/* ============ SIDEBAR OVERLAY ============ */
.sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.3);
    z-index: 99;
}

.sidebar-overlay.active { display: block; }

/* ============ MISC ============ */
.text-center { text-align: center; }
.text-right { text-align: right; }
.mt-2 { margin-top: 16px; }
.mb-2 { margin-bottom: 16px; }
.mb-1 { margin-bottom: 8px; }
.flex { display: flex; }
.flex-wrap { flex-wrap: wrap; }
.gap-2 { gap: 16px; }
.gap-1 { gap: 8px; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.hidden { display: none; }