:root {
    --accent: #2563eb;
    --muted: #6b7280;
    --bg: #f3f6fb;
    --card: #fff;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    padding: 20px;
    font-family: Inter, system-ui, Arial, sans-serif;
    background: var(--bg);
    color: #0f172a;
}

h2 {
    font-size: 20px;
    margin-bottom: 16px;
}

.controls, .columns, .actions {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin-bottom: 14px;
}

.controls > div, .columns > div {
    flex: 1;
    min-width: 180px;
}

label {
    display: block;
    font-size: 13px;
    color: var(--muted);
    margin-bottom: 6px;
}

input[type="text"], input[type="number"], input[type="date"], select {
    width: 100%;
    padding: 8px;
    border-radius: 8px;
    border: 1px solid #e6eefc;
    font-size: 14px;
    background: #fbfdff;
}

input[type="file"] {
    font-size: 14px;
}

button {
    padding: 8px 12px;
    border-radius: 8px;
    border: none;
    cursor: pointer;
    background: var(--accent);
    color: #fff;
    font-size: 14px;
}

button.secondary {
    background: #fff;
    border: 1px solid #e6eefc;
    color: var(--accent);
}

button.danger {
    background: #ef4444;
}

button.positive {
    background: #16a34a;
}

.preview table {
    width: 100%;
    border-collapse: collapse;
    margin-bottom: 12px;
}

.preview td, .preview th {
    padding: 6px 8px;
    border: 1px solid #eaeaea;
    text-align: left;
}

.headerRow {
    background: #f9fafb;
    font-weight: bold;
}

.selectedHeader {
    background: #dbeafe;
    font-weight: bold;
}

.student-list {
    margin-top: 12px;
}

.student-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: #fff;
    border-radius: 8px;
    padding: 8px 12px;
    margin-bottom: 6px;
    box-shadow: 0 4px 12px rgba(2, 6, 23, 0.05);
}

.student-item .left {
    display: flex;
    gap: 8px;
    align-items: center;
}

.student-item .small {
    font-size: 13px;
    color: var(--muted);
}

.note, .muted-note {
    font-size: 13px;
    color: var(--muted);
    margin-top: 8px;
}

@media (max-width: 920px) {
    .controls > div, .columns > div {
        min-width: 100%;
    }
    .actions {
        flex-direction: column;
        gap: 6px;
    }
}