*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0px;
}

.page {
  background-color: aquamarine;
  margin: 0px;
  width: 100%;
  display: flex;
}

.menu {
  overflow: hidden;

  /* float: left; */
  margin: 0px;
  width: 5%;
  background-color: black;
  height: 100vh;
  transition: width 0.15s ease-out;
}

button {
  position: relative;
  top: 10%;
  left: 20px;
  width: 50px;
  height: 50px;
}

.extend {
  width: 30%;
  background-color: red;
}

.content {
  flex: 1;
  background-color: blue;
  height: 100vh;
  width: auto;
}