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

html {
  height: 100%;
}

/* center stuff */
body, .modal {
  display: grid;
  align-items: center;
  justify-items: center;
  height: 100%;
}

body {
  margin: 0;
  color: #555;
  background-color: #fff;
  font: 1.25rem/1.5 'Lato', serif;
}

/* hide checkbox, but still expose it to screen readers */
input {
  position: absolute;
  width: 1px;
  clip: rect(0 0 0 0);
  overflow: hidden;
  white-space: nowrap;
}

.page-content {
  max-width: 750px;
  margin: 0 auto;
  padding: 20px;
}

h1 {
  margin: 0 0 1rem;
  font-size: 2rem;
}

p {
  margin: 0 0 1.5rem;
}

/* the "dismiss" and "show again" buttons are actually labels that toggle the checkbox */
label {
  display: block;
  padding: 20px;
  color: #fff;
  background-color: #519548;
  text-align: center;
  cursor: pointer;
}

.modal {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  background-color: #0009;
}

/* when checkbox is toggled off, dismiss modal */
#toggle-modal:not(:checked) ~ .modal {
  animation: dismiss 1s forwards;
}

@keyframes dismiss {
  to {
    opacity: 0; /* full fade out, but even an invisible element blocks stuff behind it... */
    visibility: hidden; /* ...which is where visibility comes in, to get the modal out of the way */
  }
}

/* also when checkbox is toggled off, hide dismiss button to prevent rapid clicks */
#toggle-modal:not(:checked) ~ .modal label {
  visibility: hidden;
}

.modal-box {
  max-width: 600px;
  margin: 20px 40px;
  padding: 20px;
  background-color: #fff;
}

/* user smaller font sizes on smaller screens */
@media (max-width: 580px) {
  body {
    font-size: 1rem;
  }

  h1 {
    font-size: 1.5rem;
  }
}