:root {
  --forest: #2f6b45;
  --leaf: #4d8d63;
  --sky: #2f6fa7;
  --river: #4d99d3;
  --earth: #7b5a3b;
  --sand: #f3efe7;
  --ink: #1f2b22;
  --card: #ffffff;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Verdana, Arial, sans-serif;
  color: var(--ink);
  background: linear-gradient(180deg, #f7fbf8 0%, #eef6f2 40%, #f4f1eb 100%);
  line-height: 1.6;
}

header {
  background: linear-gradient(130deg, var(--forest) 0%, var(--sky) 55%, var(--earth) 100%);
  color: white;
  padding: 2.5rem 1rem;
  text-align: center;
}

header h1 {
  margin: 0;
  font-size: clamp(1.8rem, 4vw, 2.8rem);
}

header p {
  margin-top: 0.5rem;
  font-size: clamp(1rem, 2vw, 1.2rem);
}

nav {
  background: #1f3f31;
  position: sticky;
  top: 0;
  z-index: 10;
}

nav ul {
  margin: 0;
  padding: 0.6rem 1rem;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: center;
}

nav a {
  color: white;
  text-decoration: none;
  font-size: 0.9rem;
  padding: 0.35rem 0.55rem;
  border-radius: 0.45rem;
}

nav a:hover,
nav a.active {
  background: rgba(255, 255, 255, 0.2);
}

main {
  width: min(100%, 1000px);
  margin: 1.5rem auto 3rem;
  padding: 0 1rem;
}

.card {
  background: var(--card);
  border-radius: 14px;
  padding: 1.25rem;
  box-shadow: 0 8px 20px rgba(26, 49, 36, 0.08);
  margin-bottom: 1rem;
}

h2, h3 {
  color: var(--forest);
}

.banner {
  width: 100%;
  border-radius: 12px;
  margin: 1rem 0;
  max-height: 420px;
  object-fit: cover;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1rem;
}

.note {
  background: #edf7ff;
  border-left: 5px solid var(--sky);
  padding: 0.75rem;
  border-radius: 8px;
}

ul, ol {
  padding-left: 1.2rem;
}

table {
  border-collapse: collapse;
  width: 100%;
}

table th,
table td {
  border: 1px solid #d7e2d8;
  padding: 0.6rem;
  text-align: left;
}

table th {
  background: #eef7ef;
}

.quiz-question {
  margin-bottom: 1rem;
  padding: 0.75rem;
  border: 1px solid #dce9dd;
  border-radius: 8px;
  background: #fbfefb;
}

button {
  border: 0;
  background: var(--forest);
  color: #fff;
  padding: 0.65rem 1rem;
  border-radius: 8px;
  cursor: pointer;
  font-weight: 700;
}

button:hover {
  background: var(--leaf);
}

.answer-key {
  display: none;
  margin-top: 1rem;
  background: #f5fff3;
  padding: 0.75rem;
  border-radius: 8px;
  border: 1px solid #cae6ca;
}

footer {
  text-align: center;
  padding: 1.2rem 0.8rem 2rem;
  color: #355745;
}

@media (max-width: 700px) {
  nav ul {
    justify-content: flex-start;
    overflow-x: auto;
  }

  nav a {
    white-space: nowrap;
  }
}