@charset "UTF-8";
@property --k {
  syntax: "<number>";
  initial-value: -1;
  inherits: true;
}
html, body {
  display: grid;
}

html {
  height: 100%;
}

body {
  place-content: center;
}

button {
  --m: 1;
  grid-area: 2/1/span 1/span 2;
  position: relative;
  margin: 1em;
  border: solid 2em transparent;
  padding: 1.5em 3.25em;
  border-radius: 5em;
  box-shadow: inset 0 0 1px #23429e;
  background: radial-gradient(#111a39, 67.5%, #3476da) padding-box, radial-gradient(#a0c2ed, 35%, #a0c2ed00 70%) 50% 0/80% 50% repeat-y;
  color: #f2fdfe;
  font: 700 1.5em/1 montserrat, sans-serif;
}
#slow:checked ~ button {
  --m: 5 ;
}

@keyframes k {
  0%, 33.3% {
    --k: 1 ;
  }
}
.particle {
  --f: 1;
  --pos-k: max(0, var(--k));
  --neg-k: max(0, -1*var(--k));
  --low-c: min(1, 4*(1 - var(--pos-k)));
  --abs-d: max(var(--neg-k) - .5, .5 - var(--neg-k));
  --mov-f: var(--pos-k);
  display: grid;
  position: absolute;
  left: var(--x);
  top: var(--y);
  rotate: var(--a);
  animation: k calc(var(--m)*1s) linear calc(var(--m)*var(--t, 0)*1s) infinite;
}
@supports (scale: sqrt(4)) {
  .particle {
    --mov-f: sqrt(var(--pos-k)) ;
  }
}
.particle::before, .particle::after {
  grid-area: 1/1;
  width: 0.75em;
  aspect-ratio: 1;
}
.particle::before {
  --sa: calc(min(1, 1 - 2*min(.5, var(--mov-f)))*45deg);
  border-radius: calc(1.25*min(.8, var(--mov-f))*50%) 50% 50%;
  transform-origin: 0 0;
  translate: calc(var(--mov-f)*var(--d));
  rotate: -45deg;
  scale: var(--f);
  transform: skew(var(--sa), var(--sa));
  opacity: var(--low-c);
  filter: Saturate(var(--low-c));
  background: radial-gradient(at 85% 85%, #bad9fa, #3e66a4 75%);
  content: "";
}
.particle::after {
  translate: -50% -50%;
  scale: calc(var(--f)*(1 - 2*var(--abs-d)));
  text-align: center;
  filter: blur(0.5px);
  content: "✦";
}

[type=checkbox] {
  justify-self: end;
  margin: 5px;
  width: 1em;
  aspect-ratio: 1;
}
[type=checkbox], [type=checkbox] + label {
  align-self: center;
  font: 1.25em orbitron, monospace;
  cursor: pointer;
}