/* ======== GLOBAL ======== */

body {
    margin: 0;
    padding: 0;
    background: #f2f4f7;
    font-family: Arial, sans-serif;
    color: #2c3e50;
}

/* ======== HEADER ======== */

header {
    background-color: #2c3e50;
    color: white;
    padding: 15px 30px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

/* ======== LAYOUT ======== */

.layout {
    display: flex;
    max-width: 1500px;
    margin: 20px auto;
    gap: 20px;
}

/* ======== SIDEBAR ======== */

.sidebar {
    width: 18%;
    background: #ffffff;
    padding: 20px;
    border-radius: 12px;
    box-shadow: 0 0 12px rgba(0,0,0,0.08);
    height: calc(100vh - 120px);
    overflow-y: auto;
}

.lesson-link {
    display: block;
    padding: 12px;
    margin-bottom: 10px;
    background: #eef1f5;
    border-radius: 6px;
    text-decoration: none;
    color: #2c3e50;
    font-weight: bold;
    transition: 0.2s;
}

.lesson-link:hover {
    background: #dce2ea;
}

/* ======== CONTENT ======== */

.content {
    width: 82%;
    background: #ffffff;
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 0 12px rgba(0,0,0,0.08);
    min-height: calc(100vh - 120px);
    overflow-y: auto;
}

/* ======== AD BOX ======== */

.ad-box {
    background: #fafafa;
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 25px;
    border: 1px solid #ddd;
    text-align: center;
    font-size: 14px;
    color: #555;
}

/* ======== FOOTER ======== */

footer {
    padding: 20px;
    text-align: center;
    color: #555;
    font-size: 14px;
}