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

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

.nav {
  display: flex;
  justify-content: space-around;
  background: #333;
  color: white;
  padding: 1em;
}

.layout {
  display: flex;
  flex-wrap: wrap;
  padding: 2em;
  gap: 1em;
  justify-content: center;
}

.block {
  width: 200px;
  height: 200px;
}

.block1 { background: pink; }
.block2 { background: yellow; }
.block3 { background: cyan; }
.block4 { background: orange; }
.block5 { background: #333;}

@media screen and (max-width: 768px) {
  .nav {
    flex-direction: column;
    align-items: center;
  }

  .block {
    width: 90%;
    height: 150px;
  }
}