body{
    margin:0;
    background:#f7f7f7;
    font-family: "Segoe UI", sans-serif;
}

.header{
    padding:20px;
    background:#fff;
    border-bottom:1px solid #e5e5e5;
}
.header h1{
    margin:0;
    text-align: center;
    font-size:22px;
}

.container{
    max-width: 1300px;
    margin:auto;
    padding:20px;
}


.top-section{
    display:flex;
    gap:20px;
    margin-bottom:30px;
}

.sidebar{
    width: 200px;
    background:#fff;
    padding:20px;
    border-radius:8px;
    box-shadow:0 2px 8px rgba(0,0,0,.05);
}

.sidebar h2{
    font-size:16px;
    margin-top:0;
}

.content{
    flex:1;
    background:#fff;
    padding:20px;
    border-radius:8px;
    min-height:200px;
    box-shadow:0 2px 8px rgba(0,0,0,.05);
    display:flex;
    flex-direction:column;
    gap:20px;
}

.open-btn{
    background:#2563eb;
    color:#fff;
    padding:12px 18px;
    font-size:16px;
    border:none;
    border-radius:6px;
    max-width: 300px;
    cursor:pointer;
    margin-bottom: 15px;
    margin: 0 auto;
}
.open-btn:hover{
    background:#1d4ed8;
}

.note{
    font-size:15px;
    color:#555;
    margin-top:10px;
    text-align: center;
}

.lesson-list{
    background:#fff;
    padding:20px;
    border-radius:8px;
    box-shadow:0 2px 8px rgba(0,0,0,.05);
    margin-bottom:20px;
}
.lesson-item{
    padding:10px 0;
    border-bottom:1px solid #eee;
}
.lesson-item:last-child{
    border-bottom:none;
}
.lesson-item a{
    color:#2563eb;
    text-decoration:none;
    font-size:16px;
}
.lesson-item a:hover{
    text-decoration:underline;
}


.lesson-grid{
    display:grid;
    grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
    gap: 30px;
    margin-top:20px;
}

.lesson-card{
    background:#fff;
    border-radius:10px;
    box-shadow: 0 2px 6px rgb(175 175 175 / 26%);
    overflow:hidden;
    cursor:pointer;
    opacity: .99;
    transition:transform .15s, box-shadow .15s, opacity .15s;
}

.lesson-card:hover{
    transform:translateY(-4px);
    box-shadow:0 4px 14px rgba(0,0,0,.12);
    opacity: 1;
}

.lesson-card img{
    width:100%;
    object-fit:cover;
    display:block;
}


.lesson-box {
    background: #fff;
    padding: 16px;
    border-radius: 10px;
    text-align: center;
}

.lesson_image {
    width: 200px;
    object-fit: cover;
    margin: 0 auto 10px auto;
    border-radius: 6px;
    display:block;
}

.lesson-title {
    font-size: 20px;
    font-weight: 600;
    color: #222;
}



.open-btn.big {
    padding: 14px 25px;
    font-size: 18px;
    border-radius: 8px;
}


@media (max-width: 900px) {

    .container{
        padding:15px;
    }

    .top-section{
        flex-direction:column;
    }

    .sidebar{
        width:100%;
        order:2;  
    }

    .content{
        order:1;  
    }

    .lesson-box{
        text-align:center;
    }

    .lesson_image{
        max-width:280px;
    }

    .ad-container{
        max-width:100%;
    }

    .ad-placeholder{
        max-width:728px;
        height:90px;  
        margin:0 auto;
    }
}


@media (max-width: 600px) {

    .header{
        padding:12px;
    }

    .header h1{
        font-size:18px;
    }

    .container{
        padding:12px;
    }

    .sidebar{
        padding:15px;
    }

    .content{
        padding:15px;
    }

    .lesson-grid{
        gap:18px;
        grid-template-columns: repeat(2, 1fr);
    }

    .lesson-card{
        opacity:1;
    }

    .lesson-title{
        font-size:18px;
    }

    .lesson_image{
        max-width:260px;
    }

    .ad-placeholder{
        width:100%;
        max-width:100%;
        height:250px;
    }

    .open-btn.big{
        width:100%;
        font-size:16px;
        padding:12px;
        text-align:center;
    }
}

 @media (max-width: 400px) {

    .lesson-grid{
        grid-template-columns: repeat(1, 1fr);
    }

    .sidebar h2{
        font-size:15px;
    }

    .lesson-title{
        font-size:17px;
    }

    .open-btn{
        width:100%;
    }
}

.lesson-article {
    background:#fff;
    padding:20px 25px;
    margin:20px 0;
    border-radius:10px;
    box-shadow:0 2px 8px rgba(0,0,0,0.05);
    font-family:"Segoe UI", sans-serif;
}

.lesson-article h2 {
    margin-top:0;
    font-size:20px;
    color:#111;
}

.lesson-article h3 {
    margin-top:18px;
    font-size:16px;
    color:#333;
}

.lesson-article p, .lesson-article li {
    font-size:14px;
    color:#555;
    line-height:1.6;
}

.lesson-article ul {
    margin-left:18px;
}


.home-btn {
    margin-left:auto;
    background:#2563eb;
    color:#fff;
    padding:7px 14px;
    border-radius:8px;
    text-decoration:none;
    font-size:14px;
    transition:0.2s ease;
    font-weight:600;
}

.home-btn:hover {
    background: #4078f3;
}


#lessonNewTabBtn {
    background: #6fb53c;
}

#lessonNewTabBtn:hover {
    background: #7bc546;
    cursor: pointer;
}
 
 
 
 img.lazy {
    opacity: 0;
    transition: opacity .4s ease;
}

img.lazy.loaded {
    opacity: 1;
}

.class_less{
    margin: 0 auto;
    display: grid;
    justify-content: center;
    margin-bottom: 15px;
    width: 970px;
    height: 250px;
    margin-top: 15px;
    align-items: center;
}