body {
  /* margin: 0; */
  box-sizing: border-box;
  background-color: black;
}

.red {
  width: 100px;
  height: 100px;
  background-color: red;
}

.green {
  width: 80px;
  height: 80px;
  background-color: green;
}

.blue {
  width: 60px;
  height: 60px;
  background-color: blue;
}

.yellow {
  width: 40px;
  height: 40px;
  background-color: yellow;
}

.exercise-1,
.exercise-2,
.exercise-3,
.exercise-4 {
  position: relative;
  ;
}

.exercise-1 div,
.exercise-2 div,
.exercise-3 div,
.exercise-4 div {
  position: absolute;
}

/* Exercise 2 */

.exercise-2 {
  top: 120px;
}

.exercise-2 .green,
.exercise-2 .blue,
.exercise-2 .yellow {
  top: 10px;
  left: 10px;
}

/* Exercise 3 */

.exercise-3 {
  top: 240px;
}

.exercise-3 .green {
  position: relative;
}

.exercise-3 .blue,
.exercise-3 .yellow {
  position: absolute;
  right: 0;
  bottom: 0;
}

/* Exercise 4 */

.exercise-4 {
  top: 360px;
}

.exercise-4 .blue {
  position: fixed;
  /* top: 0; */
  right: 0;
}

.exercise-4 .yellow {
  top: 0;
  right: 0;
}