:root {
    --primary: #1a73e8;
    --primary-hover: #174ea6;
    --danger: #d93025;
    --danger-hover: #a50e0e;
    --success: #1e8e3e;
    --success-hover: #0d652d;
    --bg: #f0f2f5;
    --text: #202124;
    --border: #dadce0;
    --surface: #ffffff;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg);
    color: var(--text);
    margin: 0;
    padding: 20px;
    display: flex;
    justify-content: center;
    -webkit-font-smoothing: antialiased;
}

.container {
    background: var(--surface);
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 8px 24px rgba(0,0,0,0.08);
    width: 100%;
    max-width: 400px;
    transition: box-shadow 0.3s ease;
}

.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border);
    margin-bottom: 24px;
    padding-bottom: 16px;
}

h1, h2, h3 {
    text-align: center;
    margin-top: 0;
    font-weight: 600;
}

.header h2 { margin: 0; font-size: 1.25rem; }

input, select {
    width: 100%;
    padding: 14px 16px;
    margin: 8px 0 16px 0;
    border: 1px solid var(--border);
    border-radius: 8px;
    box-sizing: border-box;
    font-size: 15px;
    transition: border-color 0.2s, box-shadow 0.2s;
    background-color: white;
}

input:focus, select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(26, 115, 232, 0.2);
}

button {
    width: 100%;
    padding: 14px 16px;
    background-color: var(--primary);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    margin: 10px 0;
    transition: background-color 0.2s, transform 0.1s;
}

button:active { transform: scale(0.98); }

.header button {
    width: auto;
    padding: 8px 16px;
    margin: 0;
    font-size: 14px;
}

button:hover { background-color: var(--primary-hover); }

.secondary-btn {
    background-color: transparent;
    color: var(--primary);
    border: 2px solid var(--primary);
}
.secondary-btn:hover {
    background-color: rgba(26, 115, 232, 0.04);
}

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

.success-btn { background-color: var(--success); }
.success-btn:hover { background-color: var(--success-hover); }

.hidden { display: none !important; }

#loading-indicator {
    text-align: center;
    margin-top: 20px;
    font-style: italic;
    color: #5f6368;
}

.student-details {
    background: #f8f9fa;
    padding: 15px;
    border-radius: 8px;
    margin: 15px 0;
    border: 1px solid var(--border);
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 20px;
    font-size: 14px;
}

th, td {
    border-bottom: 1px solid var(--border);
    padding: 12px 8px;
    text-align: left;
}

th { 
    background-color: var(--surface);
    color: #5f6368;
    font-weight: 600;
    text-transform: uppercase;
    font-size: 12px;
    letter-spacing: 0.5px;
}

tbody tr:hover {
    background-color: #f8f9fa;
}