body {
  box-sizing: border-box;
  position: relative;

  max-height: 100vh;

  font-family: serif;
  letter-spacing: 1px;
  background-image: url(./img/hintergrund.jpg);
  background-size: cover;
  background-repeat: no-repeat;
  color: #fff;
}
.container {
  position: fixed;
  right: 0;
  top: 50%;
  bottom: 50%;

  height: 95%;
  width: 50%;

  transform: translateY(-50%);
}
.titel {
  display: inline-block;
  border-bottom: 2px solid rgb(81, 171, 255);

  text-transform: uppercase;
}
#reg-form {
  min-width: 80%;
  width: 80%;
  padding: 0 20px 0 0;
}
.reg-form__container {
  width: 100%;
  padding: 10px 20px;

  letter-spacing: 5px;
}
.reg-form__container:focus-within {
  animation: Anim-reg-form__container 500ms ease-in-out infinite;
}
.reg-form__container:not(:last-child) {
  margin-bottom: 10px;
}
.reg-form__container > *:not(:last-child) {
  margin-bottom: 5px;
}
.reg-form__legende {
  font-family: "Courier New", Courier, monospace;
  font-size: 20px;
}
.reg-form__label {
  font-size: 15px;
  font-weight: 400;
}
.reg-form__umschlag {
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.reg-form__input {
  width: 300px;
  min-width: 300px;
  max-width: 300px;

  padding: 2px 2px;
}
#btn-registrieren {
  height: 35px;
  padding: 5px 10px;
  border: none;

  font-family: monospace;
  letter-spacing: 2px;
  background-color: rgb(81, 171, 255);
  color: #fff;
  cursor: pointer;

  transition: all 500ms cubic-bezier(0.39, 0.575, 0.565, 1);
}
#btn-registrieren:disabled {
  background-color: #ccc;
  color: #000;
}
#btn-registrieren:not(:disabled):hover,
#btn-registrieren:not(:disabled):focus {
  background-color: #fff;
  color: black;
}

@keyframes Anim-reg-form__container {
  0% {
    border-color: rgb(155, 205, 252);
  }
  50% {
    border-color: rgb(81, 171, 255);
  }
  100% {
    border-color: rgb(155, 205, 252);
  }
}