body {
  font-family: 'Inter', sans-serif;
  margin: 0;
  background: #0f172a;
  color: #e2e8f0;
  line-height: 1.7;
  transition: background 0.3s, color 0.3s;
}

body.light {
  background: white;
  color: #0f172a;
}

header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 10%;
  background: #020617;
  border-bottom: 1px solid #1e293b;
  transition: background 0.3s, border-color 0.3s;
}

body.light header {
  background: #f8fafc;
  border-bottom: 1px solid #e2e8f0;
}

.logo {
  font-weight: 700;
  font-size: 20px;
  color: #38bdf8;           /* bright cyan – good in both modes */
}

nav a {
  margin-right: 20px;
  text-decoration: none;
  color: #94a3b8;
  transition: color 0.2s;
}

nav a:hover {
  color: white;
}

body.light nav a {
  color: #64748b;
}

body.light nav a:hover {
  color: #0f172a;
}

#toggle {
  background: none;
  border: none;
  font-size: 1.4rem;
  cursor: pointer;
  color: inherit;
}

main {
  display: flex;
  justify-content: center;
}

.blog {
  max-width: 750px;
  padding: 60px 20px;
}

h1 {
  font-size: 40px;
  margin-bottom: 10px;
}

.meta {
  color: #94a3b8;
  margin-bottom: 40px;
}

body.light .meta {
  color: #64748b;
}

h2 {
  margin-top: 40px;
}

blockquote {
  border-left: 4px solid #38bdf8;
  padding-left: 15px;
  color: #cbd5f5;
  margin: 30px 0;
}

body.light blockquote {
  color: #1e40af;
  border-left-color: #3b82f6;
}

.diagram {
  background: #020617;
  border: 1px dashed #334155;
  padding: 20px;
  text-align: center;
  margin: 40px 0;
  border-radius: 8px;
}

body.light .diagram {
  background: #f1f5f9;
  border-color: #cbd5e1;
}

ul {
  padding-left: 24px;
}

footer {
  text-align: center;
  padding: 40px;
  border-top: 1px solid #1e293b;
  color: #94a3b8;
}

body.light footer {
  border-top: 1px solid #e2e8f0;
  color: #64748b;
}

footer button {
  margin-top: 12px;
  padding: 10px 20px;
  background: #38bdf8;
  color: white;
  border: none;
  border-radius: 6px;
  cursor: pointer;
}

footer button:hover {
  background: #0ea5e9;
}