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

html { font-size: 18px; }

body {
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
  font-size: 1rem;
  line-height: 1.55;
  color: #111;
  background: #fcfcfc;
  -webkit-font-smoothing: antialiased;
}

main {
  max-width: 85ch;
  margin: 4rem auto;
  padding: 0 1.5rem;
}

/* Nav */
nav {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  border-bottom: 1px solid #111;
  padding-bottom: 0.5rem;
  margin-bottom: 4rem;
}

.nav-brand {
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-size: 0.875rem;
}

nav ul {
  list-style: none;
  display: flex;
  gap: 1.5rem;
}

nav a {
  text-decoration: none;
  color: #111;
  font-size: 0.875rem;
  padding: 0.1em 0.2em;
}

nav a:hover {
  background: #111;
  color: #fcfcfc;
}

/* Headings */
h1 {
  font-size: 2.25rem;
  font-weight: 600;
  letter-spacing: -0.02em;
  line-height: 1.2;
  margin-bottom: 1rem;
  border-bottom: 1px solid #eee;
  padding-bottom: 1rem;
}

h2 {
  font-size: 1.35rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  margin-top: 3rem;
  margin-bottom: 1rem;
}

/* Meta / mono */
.meta {
  font-family: "Courier New", Courier, monospace;
  font-size: 0.8rem;
  color: #555;
  margin-bottom: 2rem;
}

/* Hero */
#about { margin-bottom: 3rem; }

.hero-row {
  display: flex;
  gap: 2.5rem;
  align-items: flex-start;
  margin: 2rem 0;
}

.hero-row p { flex: 1; }

.cover-figure {
  flex-shrink: 0;
  width: 200px;
}

.cover-figure img {
  width: 100%;
  height: auto;
  display: block;
  border: 1px solid #e0e0e0;
}

.cover-full {
  margin: 2rem 0 1.5rem;
}

.cover-full img {
  width: 100%;
  height: auto;
  display: block;
  border: 1px solid #e0e0e0;
}

.cover-full figcaption {
  font-family: "Courier New", Courier, monospace;
  font-size: 1.25rem;
  color: #555;
  margin-top: 0.6rem;
  font-style: italic;
}

/* Note italic */
.note { font-style: italic; color: #555; }

p + p { margin-top: 1rem; }

/* Resources */
#resources { margin-bottom: 4rem; }

.resource-list {
  list-style: none;
  border-top: 1px solid #eee;
}

.resource-list li {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  border-bottom: 1px solid #eee;
  padding: 0.9rem 0;
}

.resource-list a {
  font-weight: 500;
  text-decoration: none;
  color: #111;
}

.resource-list a:hover { text-decoration: underline; }

.resource-tag {
  font-family: "Courier New", Courier, monospace;
  font-size: 0.8rem;
  color: #888;
}

/* Chapters */
#chapters { margin-bottom: 4rem; }

.chapter-list {
  list-style: none;
  border-top: 1px solid #eee;
}

.chapter-list li { border-bottom: 1px solid #eee; }

details { padding: 0.9rem 0; }

summary {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  cursor: pointer;
  list-style: none;
  user-select: none;
}

summary::-webkit-details-marker { display: none; }

.ch-title { font-weight: 500; }

.ch-num {
  font-family: "Courier New", Courier, monospace;
  font-size: 0.8rem;
  color: #888;
  margin-left: 1rem;
  flex-shrink: 0;
}

.ch-body {
  display: flex;
  gap: 2rem;
  align-items: flex-start;
  margin-top: 1rem;
}

.ch-summary {
  flex: 1;
  color: #444;
  font-size: 0.9rem;
  line-height: 1.6;
}

.ch-figure {
  flex-shrink: 0;
  width: 340px;
}

.ch-figure img {
  width: 100%;
  height: auto;
  display: block;
  border: 1px solid #e0e0e0;
}

figcaption {
  font-family: "Courier New", Courier, monospace;
  font-size: 0.85rem;
  color: #444;
  margin-top: 0.5rem;
  font-weight: 700;
}

/* Author */
#author { margin-bottom: 4rem; }

.btn-row { margin-top: 2rem; display: flex; gap: 1rem; flex-wrap: wrap; }

.btn-primary {
  display: inline-block;
  background: #111;
  color: #fcfcfc;
  padding: 0.55rem 1.3rem;
  text-decoration: none;
  font-weight: 600;
  font-size: 0.875rem;
  letter-spacing: 0.01em;
}

.btn-primary:hover { background: #333; }

.btn-outline {
  display: inline-block;
  border: 1px solid #111;
  color: #111;
  padding: 0.55rem 1.3rem;
  text-decoration: none;
  font-weight: 600;
  font-size: 0.875rem;
}

.btn-outline:hover { background: #111; color: #fcfcfc; }

/* Footer */
footer {
  margin-top: 4rem;
  padding-top: 2rem;
  padding-bottom: 1.5rem;
  border-top: 1px solid #e0e0e0;
  font-size: 0.75rem;
  color: #aaa;
  line-height: 1.7;
}

footer a { color: #aaa; }
footer a:hover { color: #111; }

/* Responsive */
@media (max-width: 600px) {
  h1 { font-size: 1.6rem; }
  .hero-row { flex-direction: column; }
  .cover-figure { width: 100%; max-width: 220px; }
  .ch-body { flex-direction: column; }
  .ch-figure { width: 100%; max-width: 220px; }
  nav ul { gap: 1rem; }
}