Use vh/vw to break out of container

full-viewport.js

* {
  box-sizing: border-box;
}

/* This technique doesn't naturally cause horizontal overflow, but once there is natural vertical overflow, it causes horizontal overflow, so stopping here. */
body {
  overflow-x: hidden;
}

img { 
  max-width: 100%; 
}

main {
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.full-width {
  width: 100vw;
  position: relative;
  left: 50%;
  right: 50%;
  margin-left: -50vw;
  margin-right: -50vw;
}

p, figure {
  margin: 15px 0;
}
figcaption {
  text-align: center;
  color: #999;
}