body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: #0D1117;
  background: radial-gradient(circle,rgba(13, 17, 23, 1) 0%, rgba(13, 17, 23, 0.97) 100%);
  color: #e6edf3;
  margin: 0;
}

header, footer {
  background: #161b22;
  padding: 15px;
  text-align: center;
}

nav a {
  color: #58a6ff;
  margin: 0 10px;
  text-decoration: none;
}

nav a:hover {
  text-decoration: underline;
}

main {
  padding: 20px;
  max-width: 800px;
  margin: auto;
}

article {
  background: #21262d;
  border-radius: 8px;
  padding: 15px;
  margin-bottom: 10px;
  overflow: hidden;
  max-height: 80px;
  transition: max-height 0.4s ease-in-out, background 0.3s;
}

article:hover
{
  background: #2d333b;
  cursor: pointer;
  max-height: 1000px;
}

article:hover .expand {
  opacity: 1;
  visibility: visible;
  transition-delay: 0.4s;
}

article:not(:hover) {
  transition-delay: 0.5s;
}

footer a {
  color: #58a6ff;
}

.selected {
  font-weight: bold;
  text-decoration: underline;
  color: #90c4ff;

}

.expand{
  opacity: 0;
  visibility: hidden;
  margin-top: 10px;
  padding: 10px;
  border-top: 1px solid #30363d;
  transition: opacity 0.3s ease, visibility 0s linear 0.3s;
}

h3,h4 {
  margin-top: 0;
}

img {
  max-width: 100%;
  height: auto;
  padding: 15px;
  margin-bottom: 10px;
  border-radius: 8px;
}