:root {
  --main-color: #4e54c8;
  --accent-color: #8f94fb;
  --bg: #f9f9f9;
  --text: #222;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  padding: 20px;
}

header {
  text-align: center;
  margin-bottom: 30px;
}

header h1 {
  background: linear-gradient(to right, var(--main-color), var(--accent-color));
  background-clip: text;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  font-size: 3rem;
  margin-bottom: 10px;
}

nav a {
  margin: 0 10px;
  text-decoration: none;
  color: var(--main-color);
  font-weight: bold;
}

main {
  max-width: 800px;
  margin: 0 auto;
}

section {
  margin-bottom: 40px;
}

section h2 {
  font-size: 1.8rem;
  border-bottom: 2px solid var(--main-color);
  margin-bottom: 10px;
}

details summary {
  cursor: pointer;
  padding: 10px;
  background: #eee;
  border-radius: 5px;
}

footer {
  text-align: center;
  margin-top: 50px;
  font-size: 0.9rem;
  color: #777;
}

section#categories details {
  margin-bottom: 15px;
  background: #fff;
  border-radius: 8px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.1);
  padding: 10px;
  transition: 0.3s;
}

section#categories details[open] {
  background: #f0f2ff;
}

section#categories summary {
  font-weight: bold;
  font-size: 1.1rem;
  cursor: pointer;
}

section#categories ul {
  margin-top: 10px;
  padding-left: 20px;
  list-style-type: disc;
}

section#categories a {
  color: var(--main-color);
  text-decoration: none;
}

section#categories a:hover {
  text-decoration: underline;
}