html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
}

h2,
figure {
  text-align: center;
}

main {
  margin-left: 260px;
  margin-top: 51px;
}

nav {
  background-color: #EDFFE6;
  padding: 0 1em 100% 1em;
  position: fixed;
  top: 51px;
}

article {
  margin: 2em;
  scroll-margin-top: 51px;
}

figcaption {
  color: #339;
  font-weight: bold;
}

img {
  max-width: 100%;
}

ol {
  line-height: 2;
}

p {
  line-height: 1.4;
}

#header {
  position: fixed;
  top: 0;
}

.click_popup {
  cursor: pointer;
}

.click_popup:hover {
  opacity: 0.7;
}

.popup_image {
  z-index: 2;
  display: none;
}

.flex_2 {
  display: flex;
}

.flex_2.flex_center {
  justify-content: center;
}