body {
    background: #f5f7fa;
    position: relative;
    overflow-x: hidden;
}

body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='400' height='400' viewBox='0 0 400 400'%3E%3Cdefs%3E%3Cstyle%3E.f%7Bfont-family:serif;font-size:18px;fill:%23003366;opacity:0.1%7D%3C/style%3E%3C/defs%3E%3Ctext x='20' y='40' class='f'%3E∫%3C/text%3E%3Ctext x='200' y='100' class='f'%3E∑%3C/text%3E%3Ctext x='80' y='180' class='f'%3E∂%3C/text%3E%3Ctext x='300' y='250' class='f'%3E∇%3C/text%3E%3Ctext x='150' y='320' class='f'%3E∞%3C/text%3E%3CanimateTransform attributeName='transform' type='translate' values='0,0; 10,10; 0,0' dur='20s' repeatCount='indefinite'/%3E%3C/svg%3E");
    background-size: 400px 400px;
    animation: bgScroll 60s linear infinite;
}

@keyframes bgScroll {
    from { background-position: 0 0; }
    to { background-position: 400px 400px; }
}

header, main, footer {
    position: relative;
    z-index: 1;
}

/* Ограничение максимального размера всех изображений */
main img {
    max-width: 100%;
    height: auto;
    display: block;
    margin: 20px auto;
    border-radius: 4px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

/* Специальные классы для управления размером */
.img-left {
    float: left;
    max-width: 300px;
    margin: 0 20px 20px 0;
}

.img-right {
    float: right;
    max-width: 300px;
    margin: 0 0 20px 20px;
}

.img-center {
    max-width: 500px;
    margin: 20px auto;
}

.img-thumbnail {
    max-width: 150px;
    border: 2px solid #ddd;
}