.main{
        background-image: url(https://webcan-serial.kinkos-design.com/wp-content/uploads/2022/02/back-pc2.png);
    }

.main main {
    background: url(https://webcan-serial.kinkos-design.com/wp-content/uploads/2022/02/demo1-pc.png) center top no-repeat;
}

.container{
        background: #fff8ed;
    }
    
@media screen and (max-width: 768px) {
    .main{
        background-image: url(https://webcan-serial.kinkos-design.com/wp-content/uploads/2022/02/back-sp2.png);
    }

.main main {
    background: url(https://webcan-serial.kinkos-design.com/wp-content/uploads/2022/02/demo1-sp.png) center top no-repeat;
}

.container{
        background: #fff8ed;
    }

}