style.css

body {
    font-family: 'Poppins', cursive;
    display: flex;
    flex-direction: column;
    height: 100vh;
}

main {
    flex-grow: 1;
    background: url("Mathematics.jpg") no-repeat;
    background-position: center;
    background-size: cover;
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 0;
}

h1 {
    font-weight: 500;
    font-size: x-large;
    padding: 0.25rem;
    margin: 0;
}

.feet,
.marla,
.kanal,
.acre {
    color: rgba(25, 135, 84);
    text-align: center;
    font-weight: 700;
    margin-bottom: 0.50rem;
}

#warn {
    background: none;
    border-radius: 0.30rem;
}

#warn-box {
    margin: 0;
}

#warning {
    margin: 0;
    font-weight: 600;
    font-size: larger;
    text-align: center;
}

#ans1,
#ans3 {
    text-align: center;
    font-weight: 500;
    font-size: x-large;
    margin-bottom: 1.25rem;
}

#ans2,
#ans4 {
    text-align: center;
    font-weight: 500;
    font-size: x-large;
    margin-bottom: 0;
}

#submit,
#reset {
    font-weight: 500;
}

#footer h3 {
    margin: 0;
    font-size: 0.90rem;
    font-weight: 500;
    text-align: center;
}

.link {
    text-decoration: none;
}