HTML, CSS and JavaScript playground

html {
  align-items: center;
  background-color: skyblue;
  display: flex;
  justify-content: center;
}

body {
  height: 100vh;
  text-align: center;
  width: 100%;
}

.container {
  margin-left: auto;
  margin-right: auto;
  width: 80%;
}

/* START RIBBON */
nav {
  background: azure;
  border-left: 1px solid rgba(0, 0, 0, 0.4);
  border-right: 1px solid rgba(0, 0, 0, 0.4);
  box-shadow: 0 3px 1px -1px rgba(0, 0, 0, 0.4);
  margin: 40px auto 0;
  padding: 0 50px;
  position: relative;
}

nav::before,
nav::after {
  border: 1.25em solid azure;
  bottom: -0.7em;
  box-shadow: 0 2px 1px -1px rgba(0, 0, 0, 0.4);
  content: "";
  display: block;
  position: absolute;
  width: 0.6em;
  z-index: -2;
}

nav::before {
  border-left-color: transparent;
  border-right-width: 1.05em;
  left: -2.35em;
}

nav::after {
  border-left-width: 1.05em;
  border-right-color: transparent;
  right: -2.35em;
}

/* END RIBBON */

nav ul {
  display: flex;
  justify-content: space-between;
  list-style: none;
  padding: 0;
}

nav ul > li {
  float: left;
  width: 120px;
}

nav ul > li a {
  background: azure;
  color: midnightblue;
  display: block;
  font-size: 20px;
  font-weight: bold;
  height: 2em;
  line-height: 2em;
  text-align: center;
  text-decoration: none;
  text-transform: uppercase;
}

nav ul > li a:hover {
  text-decoration: underline;
}