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


body {
    font-family: Arial, Helvetica, sans-serif;
    background: #f5f6f8;
    color: #17191d;
}


/* HEADER */

.header {
    height: 75px;
    background: #111317;

    display: flex;
    align-items: center;
    justify-content: space-between;

    padding: 0 7%;
}


.logo {
    color: white;
    font-size: 19px;
    font-weight: 800;
    letter-spacing: 2px;
}


.logo span {
    font-weight: 400;
}


.back-link {
    color: white;
    text-decoration: none;
    font-size: 14px;

    transition: .2s;
}


.back-link:hover {
    opacity: .7;
}


/* PAGE */

.appointment {
    max-width: 920px;
    margin: 70px auto;

    padding: 0 20px;
}


/* INTRO */

.appointment-intro {
    text-align: center;
    margin-bottom: 35px;
}


.appointment-intro span {
    font-size: 12px;
    font-weight: bold;
    letter-spacing: 2px;
    color: #777;
}


.appointment-intro h1 {
    font-size: 44px;
    margin: 12px 0;
}


.appointment-intro p {
    color: #666;
    font-size: 17px;
    line-height: 1.6;

    max-width: 650px;
    margin: auto;
}


/* FORMULAIRE */

.appointment-form {
    background: white;

    padding: 40px;

    border-radius: 18px;

    box-shadow:
        0 15px 50px rgba(0,0,0,.07);
}


.appointment-form h2 {
    font-size: 20px;

    margin-bottom: 20px;

    padding-bottom: 12px;

    border-bottom: 1px solid #eee;
}


.form-grid {
    display: grid;

    grid-template-columns: 1fr 1fr;

    gap: 20px;

    margin-bottom: 35px;
}


.form-group {
    display: flex;
    flex-direction: column;

    gap: 8px;
}


.form-group.full {
    grid-column: 1 / -1;
}


.form-group label {
    font-size: 14px;
    font-weight: 700;
}


input,
select,
textarea {

    width: 100%;

    padding: 14px;

    border: 1px solid #ddd;

    border-radius: 9px;

    font-family: inherit;

    font-size: 15px;

    background: white;

    outline: none;

    transition: .2s;
}


input:focus,
select:focus,
textarea:focus {

    border-color: #111317;

    box-shadow:
        0 0 0 3px rgba(17,19,23,.08);
}


textarea {
    resize: vertical;
}


/* CHECKBOX */

.checkbox {

    display: flex;

    align-items: flex-start;

    gap: 10px;

    font-size: 13px;

    color: #555;

    margin-bottom: 25px;
}


.checkbox input {
    width: auto;
    margin-top: 3px;
}


/* BOUTON */

button {

    width: 100%;

    border: none;

    background: #111317;

    color: white;

    padding: 17px;

    border-radius: 9px;

    font-size: 16px;

    font-weight: 700;

    cursor: pointer;

    transition: .2s;
}


button:hover {
    transform: translateY(-1px);

    opacity: .9;
}


.form-note {

    text-align: center;

    font-size: 12px;

    color: #777;

    margin-top: 15px;
}


/* FOOTER */

footer {

    text-align: center;

    padding: 35px 20px;

    color: #777;

    font-size: 13px;

    line-height: 1.8;
}


/* MOBILE */

@media (max-width: 650px) {

    .header {
        padding: 0 20px;
    }


    .logo {
        font-size: 15px;
    }


    .appointment {
        margin: 40px auto;
    }


    .appointment-intro h1 {
        font-size: 34px;
    }


    .appointment-form {
        padding: 25px 20px;
    }


    .form-grid {
        grid-template-columns: 1fr;
    }


    .form-group.full {
        grid-column: auto;
    }

}
```