main.css

body {
  font-family: 'Poppins', sans-serif;
  background-color: #22223B;
  color: #F2E9E4;
}

.container {
  margin: 0 auto;
  text-align: center;
  width: 50%;
  height: 90vh;
  background-color: #4A4E69;
  border-radius: 15px;
}


.title {
  font-size: 50px;
  padding-top: 15%;
}

.binary-number-input-container {
  display: flex;
  justify-content: center;
}

.binary-number-input {
  width: 50%;
  height: 35px;
  border-radius: 10px;
  font-size: 20px;
  letter-spacing: 5px;
  text-align: center;
  border: 1px solid #F2E9E4;
  outline: none;
  color: #F2E9E4;
}

.binary-number-input::placeholder {
  color: #F2E9E4;
}

.binary-number-input:invalid {
  background-color: #9A8C98;
}

.binary-number-input:valid {
  background-color: #C9ADA7;
}

.validity-icon {
  font-size: 25px;
}

#is-valid-check {
  color: #C9ADA7;
  display: none;
}

#is-not-valid-cross {
  color: #9A8C98;
  display: none;
}

.convert {
  background-color: #22223B;
  color: #F2E9E4;
  width: 150px;
  height: 40px;
  border-radius: 10px;
  border: 1px solid #878fc0;
  margin-top: 2%;
}

.description-text {
  margin: 0 auto;
  text-align: center;
  width: 50%;
}

#result-text {
  font-size: 24px;
}

.fade-in-text {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 1s ease, transform 1s ease;
}

.fade-in {
  opacity: 1;
  transform: translateY(0);
}

.footer {
  text-align: center;
}

@media screen and (max-width: 600px) {
  .container {
    width: 95%;
  }

  .description-text {
    width: 100%;
  }

  #binary-number-input {
    width: 80%;
    margin: 0 auto;
    display: block;
  }
}

@media screen and (max-height: 600px) {
  .title {
    padding-top: 0;
  }
}