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

body {
    font-family: Arial, Helvetica, sans-serif;
    line-height: 1.6;
    color: #222;
    background-color: #f4f7fb;
}

.container {
    width: 100%;
    max-width: 960px;
    margin: 0 auto;
    padding: 0 1rem;
}

.site-header {
    background-color: #fff;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
    margin-bottom: 2rem;
}

.site-header .container {
    padding-top: 1rem;
    padding-bottom: 1rem;
}

.site-header h1 {
    font-size: 1.5rem;
    color: #1a5fb4;
    margin-bottom: 0.75rem;
}

.main-nav {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem 1rem;
}

.main-nav a {
    text-decoration: none;
    color: #333;
    padding: 0.35rem 0.5rem;
    border-radius: 6px;
}

.main-nav a:hover,
.main-nav a.active {
    background-color: #e8f0fa;
    color: #1a5fb4;
}

main {
    padding-bottom: 2rem;
}

section {
    margin-bottom: 2rem;
}

h2 {
    margin-bottom: 0.75rem;
    color: #1a5fb4;
}

h3 {
    margin-bottom: 0.5rem;
}

p {
    margin-bottom: 0.75rem;
}

.intro {
    background: #fff;
    padding: 1.5rem;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.06);
}

.countdown {
    font-size: 1.1rem;
    font-weight: bold;
    color: #2e7d32;
    margin: 1rem 0;
    padding: 0.75rem 1rem;
    background: #e8f5e9;
    border-radius: 8px;
    display: inline-block;
}

.btn {
    display: inline-block;
    padding: 0.65rem 1.25rem;
    border: none;
    border-radius: 8px;
    text-decoration: none;
    font-size: 1rem;
    cursor: pointer;
}

.btn-primary {
    background-color: #1a5fb4;
    color: #fff;
}

.btn-primary:hover {
    background-color: #155a9e;
}

.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 1rem;
}

.card,
.admin-card,
.feedback-card {
    background: #fff;
    padding: 1.25rem;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.06);
}

.card h3 {
    color: #1a5fb4;
}

.activity-time {
    font-size: 0.9rem;
    color: #555;
}

.registration-form {
    background: #fff;
    padding: 1.5rem;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.06);
    max-width: 520px;
}

.form-group {
    margin-bottom: 1rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.35rem;
    font-weight: bold;
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 0.6rem;
    border: 1px solid #ccc;
    border-radius: 8px;
    font-size: 1rem;
}

.form-group input.error,
.form-group select.error {
    border-color: #c62828;
}

.error-text {
    display: block;
    color: #c62828;
    font-size: 0.85rem;
    margin-top: 0.25rem;
    min-height: 1.1rem;
}

.message {
    padding: 0.75rem 1rem;
    border-radius: 8px;
    margin-bottom: 1rem;
}

.message-success {
    background: #e8f5e9;
    color: #2e7d32;
}

.message-error {
    background: #ffebee;
    color: #c62828;
}

.admin-card {
    margin-bottom: 1.5rem;
}

.admin-details {
    list-style: none;
    margin-bottom: 1rem;
}

.admin-details li {
    margin-bottom: 0.35rem;
}

.admin-table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 0.5rem;
}

.admin-table th,
.admin-table td {
    border: 1px solid #ddd;
    padding: 0.6rem;
    text-align: left;
}

.admin-table th {
    background: #e8f0fa;
}

.no-students {
    color: #666;
    font-style: italic;
}

.improvement-block {
    background: #fff;
    padding: 1.5rem;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.06);
    margin-bottom: 1.5rem;
}

.improvement-block ul {
    padding-left: 1.25rem;
}

.improvement-block li {
    margin-bottom: 0.35rem;
}

.feedback-card {
    margin-bottom: 1rem;
}

.site-footer {
    background: #fff;
    border-top: 1px solid #ddd;
    padding: 1rem 0;
    margin-top: 2rem;
    text-align: center;
    color: #666;
    font-size: 0.9rem;
}

@media (max-width: 600px) {
    .site-header h1 {
        font-size: 1.25rem;
    }

    .main-nav {
        flex-direction: column;
    }

    .admin-table {
        display: block;
        overflow-x: auto;
    }
}