index.css

@import url("https://fonts.googleapis.com/css2?family=Libre+Franklin:wght@300;400&display=swap");
* {
  box-sizing: border-box;
}
body {
  font-family: "libre franklin", sans-serif;
  font-size: 20px;
}
main {
  text-align: center;
  margin: 60px auto;
  max-width: 650px;
  padding: 20px;
}
form {
  display: flex;
  margin-top: 50px;
  position: relative;
  text-align: left;
  align-items: flex-start;
}

main h1 {
  margin-top: 13px;
  color: hsl(0, 0%, 59%);
  font-weight: 400;
  font-size: 40px;
}
main h2 {
  font-weight: 350;
  font-size: 18px;
  color: rgb(133, 133, 133);
}
form small {
  content: "nnnnnnn";
  color: hsl(354, 100%, 66%);
  font-style: italic;
  margin-left: 20px;
  display: inline-block;
  margin: 0 20px 40px;
}
.form-left {
  flex: 0.7;
}
input {
  width: 418px;
  padding: 20px 25px;
  font-size: 18px;
  border: 1px solid hsl(223, 87%, 63%);
  border-radius: 50px;
  outline: none;
  width: 100%;
  margin-bottom: 15px;
}
input.error {
  border-color: hsl(354, 100%, 66%);
}
input.error ::placeholder {
  color: hsl(354, 100%, 66%);
}

::placeholder {
  color: hsl(223, 87%, 63%);
}

form small {
  color: hsl(354, 100%, 66%);
  font-style: italic;
  margin: 0px 20px 40px;
  z-index: 100;
  display: none;
}
button {
  padding: 20px 0;
  flex: 0.3;
  font-size: 18px;
  border-radius: 50px;
  background-color: hsl(223, 87%, 63%);
  border: none;
  box-shadow: 0 5px 5px hsl(223, 100%, 88%);
  color: #fff;
  cursor: pointer;
  outline: none;
  margin-left: 15px;
}
button:hover {
  opacity: 0.85;
}
.illustration {
  margin: 30px 0;
  width: 100%;
}
.s-list {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0;
  list-style-type: none;
}
.s-list li {
  margin: 10px;
}
.s-list li a {
  border-radius: 50%;
  border: 1px solid #969696;
  color: #5093f1;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 23px;
  height: 40px;
  width: 40px;
  text-decoration: none;
}
.s-list li a:hover {
  background-color: hsl(215, 85%, 63%);
  border-color: hsl(215, 85%, 63%);
  color: #fff;
}

footer p {
  color: hsl(0, 0%, 59%);
}

@media screen and (max-width: 650px) {
  form {
    flex-direction: column;
    text-align: center;
  }
  form small {
    margin: 30px 20px;
  }
  .form-left {
    width: 100%;
  }
  button {
    margin-left: 0;
    width: 100%;
  }
}