body {
  background-color: MidnightBlue;
  color: whitesmoke;
}

.container {
    background-color: #ffffff1a; /* 8-digit hex: the last 2 digits (1a) are the alpha channel, making this white at roughly 10% opacity instead of solid */
    width: 80%;
    max-width: 600px;
    border-radius: 10px;
    margin: 20px auto;
    padding: 10px 20px;
    box-shadow: 0 5px 15px black;  
}

.center {
  text-align: center;
}

.description {
  font-size: 1.2rem;
}

fieldset {
  border: 1px solid gray;
  border-radius: 5px;
  margin: 20px 0;
  padding: 20px;
}

fieldset legend {
  font-size: 1.3rem;
  font-weight: 600;
}

label {
  font-size: 1.2rem;
}

label:not(.contact-method) { /* :not() is a negation pseudo-class — applies to every label EXCEPT ones carrying the contact-method class */
  display: block;
  margin: 10px 0;
}

input:not(.contact-method-radio-btn), /* :not() again excludes the custom radios, which get their own separate rule below */
textarea {
  background-color: #ffffff1a;
  width: 95%;
  border: 1px solid gray;
  border-radius: 5px;
  padding: 10px;
}

input,
input::placeholder, /* ::placeholder is a pseudo-element targeting the greyed hint text specifically, not the real typed value */
textarea {
  color: whitesmoke;
}


.contact-method-radio-btn {
  appearance: none; /* strips the browser's default radio styling entirely, giving a blank box to restyle from scratch */
  width: 20px;
  height: 20px;
  border-radius: 50%;
  border: 2px solid gray;
  vertical-align: bottom;
}

.contact-method-radio-btn::before {
  display: block;
  content: " ";
  width: 10px;
  height: 10px;
  border-radius: 50%;
  transform: translate(3px, 3px) scale(0); /* translate() shifts the dot to visually center it inside the circle; scale(0) starts it invisible */
  transition: all 0.3s ease-in;
}

.contact-method-radio-btn:checked::before { /* :checked matches only while this specific radio is the selected one in its group */
  transform: translate(3px, 3px) scale(1);
  background-color: lightgreen;
}

.submit-btn {
  cursor: pointer;
  background-color: royalblue;
  color: whitesmoke;
  border: none;
  border-radius: 6px;
  padding: 12px 20px;
  font-size: 1.1rem;
  display: block;
  margin: auto;
}

.submit-btn:hover {
  background-color: midnightblue;
}