style.css

@import url('https://fonts.googleapis.com/css2?family=Poppins:ital,wght@0,300;0,400;0,500;1,600&display=swap');

body{
    background-color: #2071aa;
}

.container{
    max-width: 400px;
    margin: 200px auto;
    padding: 20px;
    background-color: rgba(255, 255, 255, 0.95);
    border: 2px solid rgb(6, 11, 63);
    border-radius: 20px;
    box-shadow: 2px 2px 10px rgb(6, 11, 63);
}

h2{
    text-align: center;
    margin-top: 0px;
    margin-bottom: 30px;
    color: rgb(6, 11, 63);
    font-family: Poppins, sans-serif;
}

form{
    margin-bottom: 20px;
    display: flex;
    flex-direction: column;
}

label{
    font-size: large;
    font-family: Poppins, sans-serif;
    font-weight: 500;
    margin-bottom: 5px;
    color: rgb(6, 11, 63);
}

input[type='number'],
select{
    padding: 10px;
    border: none;
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0px 0px 3px rgba(6, 11, 63, 0.2);
    margin-bottom: 10px;
}

input[type='number']:focus,select:focus{
    outline: none;
    box-shadow: 0px 0px 4px rgba(6, 11, 63, 0.5);
}

select{
    width: 100%;
}

input[type='submit']{
    padding: 10px;
    border: none;
    background-color: rgb(6, 11, 63);
    border-radius: 10px;
    box-shadow: 0px 0px 3px rgba(6, 11, 63, 0.2);
    margin-bottom: 10px;
    color: #fff;
    font-family: Poppins, sans-serif;
    font-weight: 500;
    cursor: pointer;
}

input[type='submit']:hover{
    background-color: rgb(6, 11, 63, 0.7);
}

#result{
    font-size: 20px;
    font-family: Poppins, sans-serif;
    font-weight: 500;
    color: rgb(6, 11, 63);
    text-align: center;
    margin-top: 20px;
}