style.css

* {
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}

body {
    width: 100vw;
    overflow-x: hidden;
    background-color: rgb(239, 239, 255);
}

.game-wrapper {
    width: 100vw;
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    flex-direction: column;
}

.maindiv {
    margin-top: 25px;
    display: flex;
    flex-direction: column;
    border: none;
}

.row {
    display: flex;
}

.singlecol {
    display: flex;
    flex: 1;
    width: 80px;
    height: 50px;
    justify-content: center;
    align-items: center;
    font-size: xx-large;
    padding: 5px 20px;
    border: 1px solid black;
    cursor: pointer;
}

h1{
    font-size: 35px;
    margin-bottom: 20px;
}

#resultdiv{ 
    color: green;
    font-family: sans-serif;
}

.second-page{
    width: 100vw;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    flex-direction: column;
}

.btn-of-second-page{
    width: 150px;
    padding: 10px;
    border-radius: 15px;
    background-color: rgb(2, 120, 255);
    color: white;
    font-weight: bold;
    border: none;
    margin-top: 15px;
    cursor: pointer;
    transition: all .5s;
}

.headingofsecondpage{
    color: black !important;
}

.btn-of-second-page:hover{
    background-color: rgb(0, 94, 202);
}

/* transparent area */
.border-left {
    border-left: 1px solid transparent;
}

.border-right {
    border-right: 1px solid transparent;
}

.border-top {
    border-top: 1px solid transparent;   
}

.border-bottom {
    border-bottom: 1px solid transparent;
}

.none{
    display: none !important;
}

.red{
    color: red;
}

.white{
    color: yellowgreen;
}