* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen,
    Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
  font-size: 1.125rem;   /* 18px base */
  line-height: 1.8;      
  background: #fcfdfe;
  color: #000c18;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  overflow-x: hidden;
}

header, footer { padding: 2em; }

main {
  flex-grow: 1;
  max-width: 900px;
  margin: 0 auto;
  padding: 2em;
}

footer {
  border-top: 1px solid currentColor;
  text-align: center;
  font-size: 1.05rem; 
}

h2 {
  margin: 0 0 0.75em;
  font-weight: 700;
  line-height: 1.3;
}

h1 { font-size: 2.5rem; } 
h2 { font-size: 2rem; }  

header h1 { font-size: 2rem; }
section { margin-bottom: 3em; padding: 0 2%; }
a {
  color: #22aa44;
  font-weight: 700;
  text-decoration: underline;
  text-decoration-color: transparent;
  text-underline-offset: 4px;
  text-decoration-thickness: 2px;
  transition: color .3s, text-decoration-color .3s;
}
a:hover,
a:focus {
  color: #9966b8;
  text-decoration-color: currentColor;
}
a:focus-visible {
  outline: 3px solid #22aa44;
  outline-offset: 4px;
  border-radius: 3px;
}
header { text-align: center; }

.header-top {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 2rem;
}

nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  gap: 2rem;
  justify-content: center;
  flex-wrap: wrap;
}
nav a { 
  font-weight: 600; 
  font-size: 1.125rem; 
}
.menu-toggle {
  display: none;
  background: none;
  border: 0;
  font-size: 1.75rem;
  cursor: pointer;
  color: inherit;
}
.sr-only {
  position: absolute;
  width: 1px; height: 1px;
  margin: -1px; padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  border: 0;
}
@media (max-width: 768px) {
  h1 { font-size: 2rem; }
  h2 { font-size: 1.75rem; }
  main { padding: 1.5em; }

  .header-top {
    justify-content: space-between;
    text-align: left;
  }
  nav ul {
    flex-direction: column;
    align-items: center;
    gap: 1.25rem;
    display: none;
  }
  nav ul.open { display: flex; }
  .menu-toggle { display: block; }
  header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: inherit;
  }
}
@media (prefers-color-scheme: dark) {
  body { background: #000c18; color: #b7b8b9; }
  footer { border-color: #fcfdfe; color: #fcfdfe; }
  a { color: #22aa44; }
  a:hover, a:focus { color: #9966b8; }
}
.highlight { background: #9966b8; color: #fcfdfe; }