odin-css-exercises/flex/01-flex-center/solution/solution.css

.container {
  background: dodgerblue;
  border: 4px solid midnightblue;
  width: 400px;
  height: 300px;
}

.box {
  background: palevioletred;
  font-weight: bold;
  text-align: center;
  border: 6px solid maroon;
  width: 80px;
  height: 80px;
}

/* SOLUTION */

/* disclaimer: duplicating the `.container` selector here isn't best practice.
In your solution you probably put it right inside the existing `.container`,
which _is_ the best practice. 

We separated it out here to make it extra clear what has changed. */

.container {
  display: flex;
  align-items: center;
  justify-content: center;
}