:root {
  --red: hsl(7, 74%, 51%);
  --slider-radius: 20px;
  --slider-size: calc(2 * var(--slider-radius));
}

body {
  position: fixed;
}
html, body, #app {
  width: 100%;
  height: 100%;
}
body, #app, .slider {
  margin: 0;
}

#app {
  display: flex;
}
.slider {
  outline: none;
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
  background: transparent;
}
.slider::-webkit-slider-thumb {
  width: var(--slider-size);
  height: var(--slider-size);
  border-radius: 50%;
  background: var(--red);
  cursor: grab;
}
.slider::-moz-range-thumb {
  width: var(--slider-size);
  height: var(--slider-size);
  border-radius: 50%;
  background: var(--red);
  cursor: grab;
}
.slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
}
.slider::-webkit-slider-thumb:active {
  cursor: grabbing;
  filter: brightness(1.25);
}
.slider::-moz-range-thumb:active {
  cursor: grabbing;
}

/* because firefox is weird */
input[type=range]::-moz-focus-outer {
  border: 0;
}