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

:root {
  --grayscale-percentage: 50%;
  --inversion-percentage: 50%;
}

:disabled {
  cursor: not-allowed;
  opacity: 0.25;
}

html {
  background-color: rgb(15, 15, 15);
  margin: 0;
  display: flex;
  justify-content: center;
}

body {
  background-color: rgb(15, 15, 15);
  color: rgb(240, 240, 240);
  font-family: 'Helvetica Neue', helvetica, arial, sans-serif;
  font-size: 12pt;
  max-width: 800px;
}
h1 {
  font-size: 2rem; /* Make all H1 large, remove nested-shrinking sizes. */
  margin: 0.67em 0;
  color: red;
}

h2 {
  color: #2196f3;
  font-size: 1.5rem;
}

p {
  line-height: 1.5;
}

a {
  color: red;
  display: block;
  text-decoration: none;
  background-color: black;
  border: rgb(240, 240, 240) solid 1px;
  border-radius: 5px;
  padding: 1rem;
  text-align: center;
  margin: 0.5rem 0 1rem 0;
}

form,
section {
  background-color: rgb(45, 45, 45);
  padding: 0.5rem;
  margin: 0 0 1rem 0;
}

section {
  display: none;
  margin-top: 0.5rem;
}

div {
  display: none;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  grid-gap: 0.5rem;
}

figure {
  display: flex;
  width: 100%;
  flex-flow: column;
  margin: 0;
}

figcaption {
  background-color: #222;
  font: italic smaller sans-serif;
  padding: 0.5rem;
  text-align: center;
}

img {
  visibility: hidden;
  background-color: rgb(240, 240, 240);
  object-fit: cover;
  width: 100%;
  max-width: 100%;
  height: auto;
}

.regular {
  visibility: visible;
  filter: none;
}

.grayscale {
  visibility: visible;
  filter: grayscale(var(--grayscale-percentage));
}

.invert {
  visibility: visible;
  filter: invert(var(--inversion-percentage));
}

.grayscale-invert {
  visibility: visible;
  filter: grayscale(var(--grayscale-percentage))
    invert(var(--inversion-percentage));
}