/*
  Shared design values live here as CSS custom properties. Changing a color or
  spacing value once updates every place that uses the corresponding variable.
*/
:root {
  color-scheme: dark;
  --background-start: #07111f;
  --background-end: #102a43;
  --card-background: rgba(10, 25, 47, 0.78);
  --card-border: rgba(125, 211, 252, 0.25);
  --title-color: #f8fafc;
  --text-color: #bae6fd;
  --accent-color: #38bdf8;
  --card-radius: 1.5rem;
  --card-padding: clamp(2.5rem, 8vw, 5rem);
}

/*
  border-box makes declared widths include padding and borders, which keeps
  responsive sizing predictable. The rule applies to every page element.
*/
*,
*::before,
*::after {
  box-sizing: border-box;
}

/* Remove the browser's default page margin and inherit fonts in form controls. */
html {
  min-width: 20rem;
  min-height: 100%;
}

body {
  min-height: 100vh;
  min-height: 100svh;
  margin: 0;
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
    sans-serif;
  background:
    radial-gradient(circle at 50% 15%, rgba(56, 189, 248, 0.2), transparent 32rem),
    linear-gradient(145deg, var(--background-start), var(--background-end));
  color: var(--title-color);
}

/*
  Grid centers the card vertically and horizontally. The padding prevents the
  card from touching the screen edges on small devices.
*/
.page {
  display: grid;
  min-height: 100vh;
  min-height: 100svh;
  place-items: center;
  padding: 1.5rem;
}

/*
  The width stops growing on large screens but remains fluid on narrow screens.
  A translucent background and subtle shadow separate the message from the page.
*/
.card {
  position: relative;
  width: min(100%, 46rem);
  padding: var(--card-padding);
  overflow: hidden;
  text-align: center;
  background: var(--card-background);
  border: 1px solid var(--card-border);
  border-radius: var(--card-radius);
  box-shadow: 0 2rem 5rem rgba(0, 0, 0, 0.35);
  backdrop-filter: blur(1rem);
}

/* This narrow accent line gives the card a clear visual focus. */
.card::before {
  position: absolute;
  top: 0;
  left: 15%;
  width: 70%;
  height: 0.2rem;
  content: "";
  background: linear-gradient(90deg, transparent, var(--accent-color), transparent);
}

/* clamp() scales the heading smoothly between phone and desktop sizes. */
h1 {
  margin: 0;
  font-size: clamp(3rem, 11vw, 6.5rem);
  font-weight: 800;
  line-height: 0.95;
  letter-spacing: -0.06em;
  text-wrap: balance;
}

/* The paragraph has enough contrast and spacing to read as a calm introduction. */
p {
  margin: 1.75rem 0 0;
  color: var(--text-color);
  font-size: clamp(1.1rem, 3vw, 1.4rem);
  line-height: 1.5;
  letter-spacing: 0.04em;
}

/*
  Disable the blur effect when a browser does not support it or when transparency
  is reduced by the user's operating-system accessibility preference.
*/
@media (prefers-reduced-transparency: reduce) {
  .card {
    background: #0a192f;
    backdrop-filter: none;
  }
}