* {
  box-sizing: border-box;
}

html {
  font-size: 16px;
}

body {
  margin: 0;
  min-height: 100vh;
  padding: 0;
  font-family: sans-serif;
  display: flex;
  flex-direction: column;
  background-color: #f0f0f0;
  color: #111;
  transition: background-color 0.4s, color 0.4s;
}

img,
video {
  max-width: 100%;
  height: auto;
}

.dark-mode {
  background-color: #111;
  color: #f0f0f0;
}

.site-header {
  width: min(100%, 72rem);
  margin: 0 auto;
  padding: 1rem clamp(1rem, 3vw, 1.5rem);
}

.main-nav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  padding: 0.75rem 1rem;
  border-radius: 999px;
  background-color: rgba(17, 17, 17, 0.06);
  backdrop-filter: blur(8px);
}

.brand,
.nav-actions a,
button {
  text-decoration: none;
  color: inherit;
}

.nav-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem;
}

.nav-actions a {
  padding: 0.45rem 0.8rem;
  border-radius: 999px;
}

.app-shell {
  flex: 1;
  display: grid;
  place-items: center;
  width: min(100%, 72rem);
  margin: 0 auto;
  padding: clamp(1rem, 3vw, 2rem);
}

.clock-card {
  width: min(100%, 34rem);
  display: grid;
  gap: 0.75rem;
  justify-items: center;
  padding: clamp(1.25rem, 4vw, 2.5rem);
  border-radius: 1.25rem;
  background-color: rgba(255, 255, 255, 0.85);
  box-shadow: 0 18px 45px rgba(17, 17, 17, 0.12);
  text-align: center;
}

.eyebrow {
  margin: 0;
  font-size: 0.9rem;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  opacity: 0.8;
}

#clock {
  font-size: clamp(2.5rem, 8vw, 4.5rem);
  letter-spacing: 0.12em;
  line-height: 1.1;
}

.subtitle {
  margin: 0;
  max-width: 28rem;
  font-size: 1rem;
  opacity: 0.8;
}

button {
  padding: 0.75rem 1.25rem;
  font-size: 1rem;
  border: none;
  border-radius: 999px;
  cursor: pointer;
  background-color: #111;
  color: #f0f0f0;
  transition: background-color 0.4s, color 0.4s, transform 0.2s ease;
}

button:hover,
button:focus-visible {
  transform: translateY(-1px);
}

.dark-mode .clock-card {
  background-color: rgba(17, 17, 17, 0.8);
  box-shadow: 0 18px 45px rgba(0, 0, 0, 0.35);
}

.dark-mode button {
  background-color: #fff;
  color: #111;
}

@media (min-width: 700px) {
  .main-nav {
    padding: 0.85rem 1.25rem;
  }

  .clock-card {
    padding: 2.5rem;
  }
}