/*
  Reusable color tokens live here so a future visual refresh only requires
  changing a few values rather than searching through every selector.
*/
:root {
  --background-start: #0f172a;
  --background-end: #1d4ed8;
  --card-background: rgb(255 255 255 / 95%);
  --heading: #172554;
  --body-text: #334155;
}

/*
  Reset the browser's default page margin and ensure the page can occupy the
  full screen. The system font stack avoids downloading external font files.
*/
body {
  min-height: 100vh;
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont,
    "Segoe UI", sans-serif;
  color: var(--body-text);
  background: linear-gradient(135deg, var(--background-start), var(--background-end));
}

/*
  CSS Grid centers the message card vertically and horizontally at every
  viewport size. `padding` keeps it away from the screen edges on mobile.
*/
.hero {
  display: grid;
  min-height: 100vh;
  place-items: center;
  padding: 1.5rem;
}

/*
  The card contains all visible copy. `max-width` preserves readable line
  lengths if this basic app later grows into a longer introduction.
*/
.message {
  width: min(100%, 36rem);
  padding: clamp(2rem, 8vw, 5rem);
  text-align: center;
  background: var(--card-background);
  border-radius: 1.5rem;
  box-shadow: 0 1.5rem 3.75rem rgb(15 23 42 / 35%);
}

/* The large, responsive title is the visual focal point of the page. */
h1 {
  margin: 0;
  color: var(--heading);
  font-size: clamp(2.5rem, 9vw, 5.5rem);
  letter-spacing: -0.04em;
  line-height: 1;
}

/* This spacing separates the supporting text from the heading. */
p {
  margin: 1.25rem 0 0;
  font-size: clamp(1.1rem, 3vw, 1.5rem);
}