*,
*::after,
*::before{
    margin: 0;
    padding: 0;
    box-sizing: inherit;
}

html{
    font-size: 63%;
}

body{
    box-sizing: border-box;
}

section{
    display: flex;
    align-items: center;
    justify-content: center;
}

.section_book{
    height: 100vh;
}

.book{
    width: 60%;
    height: 60%;
    background-image: linear-gradient(105deg, rgba(255,255,255,0.9) 0%, rgba(255,255,255,0.9)50%, transparent 50%),url(/css/images/book\ flight.jpg);
    background-size: 100%;
    background-position: right;
    border-radius: 3px;
    box-shadow: 0 1.5rem 4 rem rgba(0,0,0,0.2);
}

.book__form{
    width: 50%;
    padding: 0 1rem;
}

.book-heading {
    font-size: 4rem;
    margin-bottom: 1rem;
    color: #07575b;
}

.form__group{
    margin-bottom: 2rem;
}

.form__input{
    font-size: 1.5rem;
    padding: 1rem 2rem;
    border-radius: 2px;
    background-color: rgba(196,223,230,0.4);
    border: none;
    border-bottom: 3px solid transparent;
    width: 90%;
    display: block;
    transition: all 0.3s;
}

.form__input:focus{
    outline: none;
    box-shadow: 0 1rem 2rem rgba(0,0,0,0.1);
    border-bottom: 3px solid #07575b;
    background-color: rgb(196, 223,230); 
}

.form__input:focus:invalid{
    border-bottom: 3px solid #db3030;
}

.form__input::-webkit-input-placeholder{
    color: grey;
}

.form__label{
    font-size: 1.4rem;
    font-weight: 700;
    margin-left: 2rem;
    margin-top: 0.7rem;
    display: block;
    transition: all 0.3s;
}

.form__radio-group{
    width: 100%;
    margin-top: 5px;
    margin-bottom: 12px;
    display: inline-block;
}

.form__radio-button{
    font-size: 12px;
    margin-right: 10px;
}

.form__radio_label{
    font-size: 2rem;
    cursor: pointer;
    position: relative;
    padding-left: 4.5rem;
}

.book-button .btn{
    background: #900C3F;
    width: 120px;
    color: #ffffff;
    padding: 10px 2px;
    font-weight: bold;
    border: rgb(2, 2, 2) 2px solid;
    border-radius: 20px;
    text-align: center;
    text-decoration: none;
    cursor: pointer;
    display: inline-block;
    font-size: 14px;
}

.book-button .btn:hover{
    color: white;
    background-color: black;
    transition: .7s;
}

@media screen and (max-width:600px) {

    .book{
        width: 400px;
    }

    .book-heading{
        margin-bottom: 1rem;
    }

    .book__form{
        padding: 0;
    }

    .book-button{
        margin-top: 10px;
    }

    .book-heading{
        font-size: 14px;
    }
}