:root{
  --bg: #ffffff;
  --text: #111111;
  --muted: #555555;
  --border: #e6e6e6;
  --primary: #2563eb;
  --card: #fafafa;

  --container: 1000px;
  --radius: 10px;
}

*{ box-sizing: border-box; }

body{
  margin: 0;
  font-family: Arial, "Noto Sans", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.8;
}

a{ color: inherit; text-decoration: none; }

img{ max-width: 100%; display: block; }

.container{
  width: min(100% - 24px, var(--container));
  margin-inline: auto;
}

.site-header{
  border-bottom: 1px solid var(--border);
  background: #fff;
  position: sticky;
  top: 0;
}

.nav{
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 12px 0;
}

.brand{
  font-weight: 700;
}

.nav-links{
  list-style: none;
  display: flex;
  gap: 12px;
  margin: 0;
  padding: 0;
  flex-wrap: wrap;
}

.nav-links a{
  padding: 6px 10px;
  border-radius: 8px;
  color: var(--muted);
}

.nav-links a:hover{
  background: #f3f4f6;
  color: var(--text);
}

.nav-links a.active{
  background: #eef2ff;
  color: var(--text);
}

.nav-github{
  color: var(--primary);
  font-weight: 700;
}

.hero{
  width: 100%;
  padding: 48px 0;
  background: #f8fafc;
  border-bottom: 1px solid var(--border);
}

.hero h1{
  margin: 0 0 8px;
  font-size: 40px;
}

.slogan{
  margin: 0 0 16px;
  color: var(--muted);
}

.btn{
  display: inline-block;
  padding: 10px 14px;
  border-radius: 10px;
  background: var(--primary);
  color: #fff;
  font-weight: 700;
}

.btn:hover{
  filter: brightness(0.95);
}

.section{
  padding: 28px 0;
}

.muted{
  color: var(--muted);
  margin-top: 0;
}

.features{
  display: grid;                  /* MUST: CSS Grid */
  grid-template-columns: repeat(3, 1fr); /* Desktop: 3 cards */
  gap: 12px;
  margin-top: 12px;
}

.card{
  border: 1px solid var(--border);
  background: var(--card);
  border-radius: var(--radius);
  padding: 14px;
}

.icon{
  width: 34px;
  height: 34px;
  margin-bottom: 8px;
}

.card h3{
  margin: 6px 0;
  font-size: 16px;
}

.card p{
  margin: 0;
  color: var(--muted);
}

.doc{
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px;
  margin-top: 12px;
  background: #fff;
}

.doc h3{
  margin: 0 0 8px;
}

.gallery{
  display: flex;                 /* MUST: Flexbox */
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 12px;
}

.shot{
  flex: 1 1 260px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  background: #fff;
}

.shot img{
  height: 190px;
  width: 100%;
  object-fit: cover;
  transition: transform .18s ease, opacity .18s ease; /* Hover effect */
}

.shot:hover img{
  transform: scale(1.05);
  opacity: 0.92;
}

.shot figcaption{
  padding: 10px 12px;
  color: var(--muted);
  border-top: 1px solid var(--border);
  font-size: 14px;
}

.footer{
  border-top: 1px solid var(--border);
  padding: 16px 0;
  background: #fff;
  margin-top: 16px;
}

/* MUST: Responsive < 768px
   - menu OK
   - feature grid becomes 1 column
*/
@media (max-width: 768px){
  .nav{
    flex-wrap: wrap;
  }

  .features{
    grid-template-columns: 1fr; /* Mobile: 1 column */
  }

  .hero h1{
    font-size: 32px;
  }
}