style.css

.parent {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    grid-template-rows: repeat(5, 1fr);
    grid-column-gap: 2px;
    grid-row-gap: 2px;
    }
    
    .div1 { grid-area: 1 / 1 / 2 / 2; }
    .div2 { grid-area: 1 / 2 / 2 / 3; }
    .div3 { grid-area: 1 / 3 / 2 / 4; }
    .div4 { grid-area: 1 / 4 / 2 / 5; }
    .div5 { grid-area: 1 / 5 / 2 / 6; }
    .div6 { grid-area: 2 / 1 / 3 / 2; }
    .div7 { grid-area: 2 / 2 / 3 / 3; }
    .div8 { grid-area: 2 / 3 / 3 / 4; }
    .div9 { grid-area: 2 / 4 / 3 / 5; }
    .div10 { grid-area: 2 / 5 / 3 / 6; }
    .div11 { grid-area: 3 / 1 / 4 / 2; }
    .div12 { grid-area: 3 / 2 / 4 / 3; }
    .div13 { grid-area: 3 / 3 / 4 / 4; }
    .div14 { grid-area: 3 / 4 / 4 / 5; }
    .div15 { grid-area: 3 / 5 / 4 / 6; }
    .div16 { grid-area: 4 / 1 / 5 / 2; }
    .div17 { grid-area: 4 / 2 / 5 / 3; }
    .div18 { grid-area: 4 / 3 / 5 / 4; }
    .div19 { grid-area: 4 / 4 / 5 / 5; }
    .div20 { grid-area: 4 / 5 / 5 / 6; }
    .div21 { grid-area: 5 / 1 / 6 / 2; }
    .div22 { grid-area: 5 / 2 / 6 / 3; }
    .div23 { grid-area: 5 / 3 / 6 / 4; }
    .div24 { grid-area: 5 / 4 / 6 / 5; }
    .div25 { grid-area: 5 / 5 / 6 / 6; }