css
/* style.css */
body {
  background-color: #f7f7f7;
  font-family: 'Arial', 'sans-serif';
  font-weight: bold;
}

h1 {
  color: #ff0000;
  border-bottom: 4px solid #000000;
}

h2 {
  color: #00ff00;
  border-bottom: 4px solid #000000;
}

h3 {
  color: #0000ff;
  border-bottom: 4px solid #000000;
}

a {
  text-decoration: none;
  color: #000000;
  border-bottom: 4px solid #000000;
}

a:hover {
  color: #000000;
  background-color: #ffffff;
  border-bottom: 4px solid #000000;
}

body > * {
  margin: 0;
  padding: 0;
}

body > *::before {
  content: "";
  display: block;
  clear: both;
  visibility: hidden;
}

body > *::after {
  content: "";
  display: table;
  clear: both;
  visibility: visible;
}

/* Experimental Phase */
h1 {
  font-size: 24px;
  font-weight: 700;
  line-height: 1;
  margin: 0;
  padding: 20px;
  border-bottom: 4px solid #000000;
  background-image: linear-gradient(to bottom, #000000, #ffffff);
  background-size: 100% 1px;
  background-position: 0 1;
  background-repeating: no-repeat;
}

h2 {
  font-size: 20px;
  font-weight: 600;
  line-height: 1.2;
  margin: 0;
  padding: 10px;
  border-bottom: 4px solid #000000;
  background-image: linear-gradient(to bottom, #000000, #000000);
  background-size: 100% 1px;
  background-position: 0 1;
  background-repeating: no-repeat;
}

h3 {
  font-size: 18px;
  font-weight: 500;
  line-height: 1.3;
  margin: 0;
  padding: 5px;
  border-bottom: 4px solid #000000;
  background-image: linear-gradient(to bottom, #000000, #000000);
  background-size: 100% 1px;
  background-position: 0 1;
  background-repeating: no-repeat;
}