body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
}

header {
  background-color: #333;
  color: #fff;
  padding: 1rem;
}

nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
}

nav li {
  margin-right: 1rem;
}

nav a {
  color: #fff;
  text-decoration: none;
}

main {
  max-width: 960px;
  margin: 0 auto;
  padding: 1rem;
}

section {
  margin-bottom: 2rem;
}

h2 {
  margin-top: 0;
}

.video-grid {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
}

.video-thumbnail 
  width:calc(33.33% - 1rem);