Blue-based stylesheet

html {
  font-family: "courier new", monospace;
  margin-top: 10px;
  border: 5px solid #6666ff;
  display: block;
}

body {
  background: black;
  color: white;
  max-width: 350px;
  width: 100%;
  margin: 0 auto;
  padding: 10px;
}
.welcome {
  color: mediumpurple;
  font-size: 30px;
  text-align: center;
  background: white;
}

.intro {
  color: white;
  background: none;
}

#name,
#email,
#number,
textarea {
  font-family: monospace;
  width: 95%;
  border-radius: 10px;
  margin: 10px 10px 10px 0;
  min-height: 2em;
}
p {
  font-size: 18px;
  color: black;
  background: white;
  padding: 5px;
  border-radius: 10px;
}
h1 {
  font-size: 30px;
  text-align: center;
  border: 5px solid mediumslateblue;
  padding: 5px;
  margin: 10px;
}

hr {
  border: 10px double mediumslateblue;
}

.comment {
  border: 5px solid mediumslateblue;
  padding: 15px;
  margin-bottom: 10px;
}

#radio {
  margin-top: 10px;
}

textarea {
  font-family: monospace;
  color: #6666ff;
}

button {
  font-family: monospace;
  color: white;
  background-color: #6666ff;
  border-radius: 10px;
}

input {
  background-color: #ffffff;
  color: #6666ff;
  margin: 0 auto;
}

placeholder {
  color: mediumpurple;
}

/* Other Css */

* {
  font-family: "Courier New", monospace;
}
html {
  border: 10px solid #66f;
}
body {
  background: #000;
  margin: 0 auto;
  padding: 10px 15px;
  line-height: 26px;
}
h1 {
  font-size: 30px;
  text-align: center;
  border: 5px solid #66f;
  padding: 5px;
  margin: 10px;
}
h1,
.welcome {
  text-align: center;
  font-weight: bold;
}
h1 {
  color: #66f;
  font-size: 30px;
  border: 5px groove #66f;
  box-shadow: 5px 5px 5px #66f;
}
.welcome {
  color: #66f;
  background: #fff;
}
#description {
  color: #fff;
  background-image: conic-gradient(#66f, #000, #66f, #000, #66f, #000);
  box-shadow: 5px 5px 5px #66f;
}

hr {
  border: 10px double #66f;
  box-shadow: 5px 5px 5px #66f;
}

.comment {
  border: 5px solid mediums lateblue;
  padding: 15px;
  margin-bottom: 10px;
}

#register {
  max-width: 350px;
}

#register2 {
  max-width: 350px;
}

#register2 p {
  margin-top: 20px;
}

label {
  color: #66f;
  font-weight: bold;
  display: block;
  width: 130px;
  float: left;
}
label:after {
  content: ": ";
}

input {
  color: #66f;
  padding: 3px;
  box-shadow: 31px 13px 15px #66f;
  font-size: 14px;
  font-weight: 600;
  width: 50%;
  background-color: #000;
  border: 1px solid #fff;
}

::placeholder {
  color: #99f;
}

textarea {
  color: #66f;
}
#button {
  padding: 5px;
  border: 5px outset #99f;
  background-color: #66f;
  border-radius: 10px;
  display: block;
  margin-left: auto;
  margin-right: auto;
  width: 80px;
  font: inherit;
}
#button:focus {
  outline: 2px solid gray;
  font-weight: bold;
  color: #000;
  background-color: #66f;
}

#button:hover {
  color: #66f;
  background-color: #000;
  box-shadow: 3px 3px 5px grey;
  cursor: pointer;
}