:root {
    --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    --text-color: #333;
    --bg-color: #fff;
    --btn-border: #4caf50;
    --btn-text: #4caf50;
    --link-blue: #0d6efd;
    --title-red: #dc3545;
}

body {
    font-family: var(--font-family);
    color: var(--text-color);
    background-color: var(--bg-color);
    margin: 0;
    padding: 20px;
    line-height: 1.6;
}

.container {
    display: flex;
    flex-direction: column;
    max-width: 1100px;
    margin: 0 auto;
    gap: 40px;
}

@media (min-width: 768px) {
    .container {
        flex-direction: row;
    }
}

.sidebar {
    flex: 0 0 240px;
}

.sidebar h2 {
    font-size: 18px;
    margin-top: 0;
    margin-bottom: 20px;
    color: #333;
}

.month-group {
    margin-bottom: 20px;
    line-height: 2.2;
}

.month-title {
    font-weight: 700;
    font-size: 14px;
    margin-right: 4px;
    color: #333;
}

.date-btn {
    display: inline-block;
    padding: 2px 7px;
    border: 1px solid var(--btn-border);
    color: var(--btn-text);
    border-radius: 3px;
    font-size: 13px;
    text-decoration: none;
    background-color: #fff;
    margin-right: 2px;
    margin-bottom: 4px;
    line-height: 1.4;
    transition: all 0.2s;
    cursor: pointer;
}

.date-btn:hover, .date-btn.active {
    background-color: #f0fdf4;
    font-weight: bold;
}

.content {
    flex: 1;
    min-width: 0;
}

.header-box {
    border: 1px solid #dee2e6;
    border-radius: 0;
    margin-bottom: 20px;
    background-color: #f8f9fa;
}

.header-box-top {
    background-color: #e9ecef;
    padding: 10px 15px;
    font-weight: bold;
    color: #212529;
    border-bottom: 1px solid #fff;
}

.header-box-bottom {
    padding: 10px 15px;
    color: #495057;
}

.teacher-info {
    font-size: 14px;
    color: #6c757d;
    margin-bottom: 5px;
}

.in-class-link {
    color: var(--link-blue);
    font-weight: bold;
    text-decoration: none;
    font-size: 16px;
    display: inline-block;
    margin-bottom: 15px;
}

.in-class-link:hover {
    text-decoration: underline;
}

.activity-section {
    margin-bottom: 25px;
}

.activity-item {
    margin-bottom: 8px;
    font-size: 15px;
}

.activity-item strong {
    color: #212529;
}

.sub-list {
    margin-top: 5px;
    margin-bottom: 15px;
    padding-left: 20px;
    color: #212529;
}

.sub-list li {
    margin-bottom: 3px;
    font-size: 15px;
}

hr {
    border: 0;
    border-top: 1px solid #dee2e6;
    margin: 25px 0;
}

.homework-title {
    color: var(--title-red);
    font-weight: bold;
    font-size: 16px;
    margin-bottom: 15px;
}

.homework-block {
    margin-bottom: 15px;
}

/* Admin Styles */
.ql-editor {
    min-height: 150px;
    font-family: var(--font-family);
    font-size: 15px;
}
.editor-container {
    margin-bottom: 20px;
    background: #fff;
}
.admin-section-title {
    margin-bottom: 5px;
    font-weight: bold;
    color: #212529;
}
.btn-save {
    background-color: var(--btn-border);
    color: white;
    border: none;
    padding: 10px 20px;
    font-size: 16px;
    border-radius: 4px;
    cursor: pointer;
    font-weight: bold;
}
.btn-save:hover {
    background-color: #388e3c;
}
#save-msg {
    margin-left: 10px;
    font-weight: bold;
}