:root {
  --color-bg: #ccc;
  --color-fg: #000;
  --color-clock-bg: #fff;
}

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

html,
body {
  height: 100dvh;
}

html {
  font-size: 100%;
}

body {
  margin: 0;
  padding: 1rem;
  display: flex;
  flex-direction: column;
  font-family: monospace;
  font-size: 1rem;
  background-color: var(--color-bg);
  color: var(--color-fg);
}

.header {
  flex-shrink: 0;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
}

.header__title {
  margin: 0;
  font-size: 1rem;
  font-weight: 400;
}

.main {
  flex: 1 1 auto;
  display: flex;
  justify-content: center;
  align-items: center;
}

.clock {
  display: flex;
  align-items: flex-start;
  border: 0.0625rem solid;
  height: 1lh;
  background-color: var(--color-clock-bg);
}

.clock__display {
  display: flex;
  align-items: flex-start;
}

.clock__display:not(:has(.clock__tape--period))
  + .clock__display::before {
  content: ":";
}

.clock__display:has(.clock__tape--period)::after {
  content: "-";
}

@keyframes transform-tape {
  to {
    transform: translateY(-100%);
  }
}

.clock__tape {
  /* Modifier to speed up the animation (debug) */
  --duration-modifier: 1;

  animation: transform-tape
    calc(var(--duration) / var(--duration-modifier))
    calc(
      var(--offset, var(--default-offset, 0s)) / var(--duration-modifier)
    )
    steps(var(--steps), end) infinite;
}

.clock__tape--period {
  --duration: 86400s;
  --steps: 2;
}

.clock__tape--hours {
  --duration: 43200s;
  --steps: 12;
  --default-offset: -39600s;
}

.clock__tape--minutes-tenth {
  --duration: 3600s;
  --steps: 6;
}

.clock__tape--minutes-single {
  --duration: 600s;
  --steps: 10;
}

.clock__tape--seconds-tenth {
  --duration: 60s;
  --steps: 6;
}

.clock__tape--seconds-single {
  --duration: 10s;
  --steps: 10;
}