style.css

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
.section{
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    height: 100vh;
}
.heading{
    font-size: 2.5rem;
    margin-bottom: .5rem;
}
.container{
    display: grid;
    width: 500px;
    height: 500px;
    z-index: 1000;
    border: none;
    box-shadow: 
    5px 5px 10px 0 rgba(0, 0, 0, 0.25),
    -5px -5px 10px 0 rgba(0, 0, 0, 0.25),
    inset -5px -5px 20px 0 rgba(255, 255, 255, 1);
}
.buttons{
    margin: 1rem;
}
.btn{
    padding: .5rem 1rem;
    margin: 2rem;
    background: transparent;
    cursor: pointer;
    font-size: 1rem;
    outline: none;
    border: none;
    box-shadow: 
    5px 5px 10px 0 rgba(0, 0, 0, 0.25),
    inset -5px -5px 20px 0 rgba(255, 255, 255, 1);
    border-radius: 5px;
}