:root {
  --header-height: 60px;
  --sidebar-width: 200px;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: 'Courier New', monospace;
  line-height: 1.5;
  color: #000;
  background-color: #fff;
  padding-top: var(--header-height);
  max-width: 1200px;
  margin: 0 auto;
}

header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: var(--header-height);
  background: #fff;
  border-bottom: 1px solid #000;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
}

nav {
  position: fixed;
  top: var(--header-height);
  left: 0;
  width: var(--sidebar-width);
  height: calc(100% - var(--header-height));
  border-right: 1px solid #000;
  background: #fff;
  padding: 1rem;
  overflow-y: auto;
}

nav a {
  display: block;
  margin-bottom: 1rem;
  text-decoration: none;
  color: #000;
}

main, .content {
  padding: 2rem;
  padding-top: var(--header-height);
  max-width: 900px;
  margin-right: auto;
  margin-left: auto;
}

@media (min-width: 1024px) {
  main, .content {
    margin-left: 220px;
  }
}

h1, h2, h3, h4, h5, h6 {
  margin-bottom: 1rem;
}

p {
  margin-bottom: 1rem;
}

button {
  background: none;
  border: 1px solid #000;
  font-family: 'Courier New', monospace;
  padding: 5px 10px;
  cursor: pointer;
}

button:hover {
  background-color: #f0f0f0;
}

@media (max-width: 768px) {
  nav {
    display: none;
  }
  main, .content {
    margin: 0 auto;
    padding: 1rem;
    padding-top: var(--header-height);
  }
}
img {
  max-width: 100%;
  height: auto;
  display: block;
  margin: 2rem auto;
}
figure {
  max-width: 100%;
  margin: 2rem auto;
  padding: 0;
  text-align: center;
}

figcaption {
  font-size: 0.9rem;
  color: #555;
  font-style: italic;
  margin-top: 0.5rem;
}