*{box-sizing: border-box;margin: 0; padding: 0;}
main{background: rgb(72, 75, 75);
padding: 1rem;}
section{ display: grid; background: rgb(255, 255, 255);
    grid-template-columns: repeat(4,1fr);
    grid-template-rows: repeat(4,120px);

}
article{border-radius: 1rem; margin: 1rem}
#a1{
background:darkred ;
grid-area: 1 / 1 / 3 / 3;
z-index: 2;
}
#a2{
background:rgb(141, 16, 16) ;
grid-area: 2 / 2 / 4 / 4;
z-index: 1;
}
#a3{
background:rgb(146, 36, 36) ;
grid-area: 3 / 3 / 5 / 5;
z-index: 0 ;
}
#a4{
    background-color:rgba(155, 65, 65, 0.555) ;
    z-index: 4;
    grid-area: 1 / 1 / 5 / 5;
    margin: 3rem;
}