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

body, html {
  background-color: #000050;
  height: 100%;
  font-family: "Open Sans", sans-serif;
  font-optical-sizing: auto;
  font-weight: <weight>;
  font-style: normal;
  color: #fff;
  font-variation-settings:"wdth" 100;
  width: 100%;
}

#logo {
  position: fixed;
  top: 40px;
  left: 20px;
  width: 100%;
  max-width: 1080px;
  left: 50%;
  transform: translate(-50%, 0); 
  padding: 20px;
  background: transparent;
  z-index: 10;
  text-align: left;
}

#footer {
  position: fixed;
  bottom: 0;
  left: 0;
  color: #7878FF !important;
  width: 100%;
  padding: 1rem;
  font-size: 11px;
  background: transparent;
  z-index: 10;
  text-align: center;
}

main {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  height: 100%;
  position: relative;
  width: 100%;
  max-width: 100%;
  margin: 0 auto;
  text-align: center;
  padding: 2rem;
}

#zone-une {
  z-index: 2;
}

h1 {
  font-family: helvetica, arial;
  font-size: 50px;
  font-weight: lighter;
  line-height: 1.2em;
  margin-bottom: 20px;
}

p {
  font-size: 18px;
  line-height: 1.2em; 
  margin-bottom: 60px;
}

.btn {
  background: #2424BC;
  border-radius: 22px;
  color: #fff;
  font-size: 14px;
  font-weight: bold;
  padding: 11px 30px;
  text-decoration: none;
  animation: background-color 4s ease-in;
  
}

.btn:hover{
  background-color: #191991;
}

#pattern img {
  position: absolute;
  z-index: 1;
  opacity: 1;
}

#pattern img.pattern-l {
  height: 518px;
  width: 428px;
  left: 0;
  bottom: 0;
}

#pattern img.pattern-r {
  height: 100%;
  width: auto;
  right: 0;
  top: 0;
}

@media screen and (max-width: 640px) {
  
    h1{
      font-size: 38px;
    }
  
    #pattern img.pattern-l {
      left: -300px;
    }
  
}