:root {
  --bg: #ffffff;
  --text: #1a202c;
  --link: #1a365d;
  --focus: #2b6cb0;
  --border: #e2e8f0;
  --ad-bg: #f7fafc;
}
* { box-sizing: border-box; }
html { font-size: 100%; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  max-width: 100%;
  overflow-x: hidden;
}
.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--focus);
  color: #fff;
  padding: 0.5rem 1rem;
  z-index: 100;
}
.skip:focus { left: 0; }
header, main, footer { padding: 1rem; max-width: 48rem; margin: 0 auto; }
nav a { margin-right: 1rem; color: var(--link); text-decoration: none; }
nav a:hover, nav a:focus { text-decoration: underline; }
a:focus, button:focus, input:focus {
  outline: 3px solid var(--focus);
  outline-offset: 2px;
}
h1 { font-size: 1.75rem; margin-top: 0; }
h2 { font-size: 1.35rem; }
.cards { list-style: none; padding: 0; }
.cards li { margin-bottom: 1rem; border: 1px solid var(--border); border-radius: 0.5rem; }
.cards a { display: block; padding: 1rem; color: inherit; text-decoration: none; }
.cards a:hover, .cards a:focus { background: #f7fafc; }
.catalog { list-style: none; padding: 0; }
.catalog li { margin-bottom: 1.5rem; padding-bottom: 1rem; border-bottom: 1px solid var(--border); }
.ad {
  background: var(--ad-bg);
  border: 1px solid var(--border);
  padding: 0.75rem;
  margin-bottom: 1rem;
  font-size: 0.9rem;
}
.ad span { font-weight: 700; margin-right: 0.5rem; }
footer nav { margin-top: 1rem; }
#search-container { margin: 1rem 0; }
#search-container input { padding: 0.5rem; width: 100%; max-width: 20rem; margin-right: 0.5rem; }
#search-container button { padding: 0.5rem 1rem; background: var(--link); color: #fff; border: 0; border-radius: 0.25rem; cursor: pointer; }
[hidden] { display: none !important; }
@media (min-width: 640px) {
  .cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(16rem, 1fr)); gap: 1rem; }
  .cards li { margin: 0; }
}