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

body {
  font-family: Arial, Helvetica, sans-serif;
}

main {
  margin-left: 5px;
}

h1,
h2 {
  margin: 0.25em 0;
  text-align: center;
}

section {
  border: 1px solid red;
}

section.fixed-height {
  height: 300px;
}

p {
  margin-top: 25px;
}

div {
  width: 100px;
  height: 100px;
  background-color: darkslateblue;
  color: white;
}

.flex {
  display: flex;
}

.gap {
  gap: 5px;
}

.align-item {
  align-items: center;
}

.justify-center {
  justify-content: center;
}

.justify-space-around {
  justify-content: space-around;
}

.justify-space-between {
  justify-content: space-between;
}

.justify-space-evenly {
  justify-content: space-evenly;
}

.justify-end {
  justify-content: end;
}

.dont-shrink div {
  flex-shrink: 0;
}

.overflow-hidden {
  overflow: hidden;
}

.overflow-auto {
  overflow: auto;
}

.wrap {
  flex-wrap: wrap;
}

.flex-grow div {
  flex-grow: 1;
}

/* ====== column ====== */

.column-flex {
  flex-direction: column;
}