.formulaire {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
}

.cadre {
    position: relative;
    padding: 50px 50px;
    background: #fff;
    border-radius: 10px;
    background:purple;
}

.cadre h1 {
    letter-spacing: 5px;
    margin-bottom: 60px;
    font-weight: bold;
    padding-left: 10px;
  }
  
  .cadre .inputbox {
    position: relative;
    width: 300px;
    height: 50px;
    margin-bottom: 25px;
  }
  .cadre .inputbox input {
    width: 100%;
    border: 2px solid #000;
    outline: none;
    background: none;
    padding: 10px;
    border-radius: 10px;
    font-size: 1.2em;
  }
  
  .cadre .inputbox span {
    position: absolute;
    top: 14px;
    left: 20px;
    font-size: 1em;
    transition: 0.3s;
    font-family: sans-serif;
  }
  
  .span_date{
    margin-left: 7px;
    font-size: 1em;
    font-family: sans-serif;
  }
  
  .cadre .inputbox input:focus ~ span,
  .cadre .inputbox input:valid ~ span {
    transform: translateX(-13px) translateY(-35px);
    font-size: 1em;
  }
  
input[type="submit"], #buttonTEL{
    border: none;
    border-radius: 5px;
    border: 2px solid #000;
    margin: 10px 0px 0px 25%;
    padding: 20px 10% 20px 10%;
}