:root {
  --text-color: rgb(255, 249, 228);
  --halo-color: rgb(253, 251, 159, 0.8);
  --halo-blur: 1rem;
  --background-color: #011627;

  --space: 1rem;
  --space-s: 0.5rem;

  --control-border-color: #f1e9ff;
  --control-background-color: rgba(14, 59, 94, 0.8);
  --control-halo-color: #9863fa;
  --control-halo-width: 20px;
  --control-border-width: 5px;
  --control-radius: 2px;
  --control-width: 20rem;
  /* Low enough to recede, high enough to keep 4.5:1 contrast on the panel. */
  --hint-opacity: 0.7;

  --control-text-color: var(--control-border-color);
  --control-button-halo: var(--control-halo-color);
}

body {
  box-sizing: border-box;
  min-height: 100vh;
  margin: 0;
  padding: var(--space);
  background: var(--background-color);
  color: var(--text-color);
  font-family: sans-serif;
  display: grid;
  grid-template:
    "title controls" 1fr
    "link link" auto
    / 1fr auto;
  align-items: center;
  gap: var(--space);
}

main {
  grid-area: title;
}

h1 {
  margin: 0;
  text-align: center;
  font-size: clamp(2.5rem, 10vw, 5rem);
  text-shadow: 0 0 var(--halo-blur) var(--halo-color);
}

snow-fall {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
}

snow-fall:not([data-in-front]) {
  z-index: -1;
}

.github-link {
  grid-area: link;
  justify-self: end;
  display: flex;
  align-items: center;
  gap: var(--space-s);
  color: inherit;
  text-decoration: none;
}

.github-link:hover {
  text-shadow: 0 0 var(--halo-blur) var(--halo-color);
}

#controls {
  grid-area: controls;
  position: relative;
  box-sizing: border-box;
  width: var(--control-width);
  max-width: 100%;
  display: flex;
  flex-direction: column;
  gap: var(--space);
  padding: var(--space);
  border: var(--control-border-width) solid transparent;
  border-radius: var(--control-radius);
  background: var(--control-background-color);
  color: var(--control-text-color);
}

#controls::after {
  pointer-events: none;
  content: "";
  position: absolute;
  inset: calc(0px - var(--control-border-width));
  border: var(--control-border-width) solid var(--control-border-color);
  border-radius: var(--control-radius);
  box-shadow:
    0 0 var(--control-halo-width) var(--control-halo-color),
    inset 0 0 var(--control-halo-width) var(--control-halo-color);
}

#controls > .control {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-s) var(--space);
}

#controls > .control:hover > label {
  text-shadow: 0 0 var(--halo-blur) var(--control-button-halo);
}

#controls > .control > label {
  cursor: pointer;
}

#controls > .control > input[type="text"],
#controls > .control > input[type="number"] {
  flex: 1 1 0;
  min-width: 0;
}

#controls > .control > input[type="checkbox"] {
  margin: 0;
}

#controls > .control > .hint {
  flex-basis: 100%;
  font-size: smaller;
  opacity: var(--hint-opacity);
}

/* Media queries can't read custom properties: roughly title + --control-width. */
@media (width < 45rem) {
  body {
    grid-template:
      "title"
      "controls"
      "link";
    justify-items: center;
    padding-bottom: var(--space-s);
  }

  .github-link {
    justify-self: center;
    align-self: end;
  }
}