:root {
  color-scheme: dark;
  --background: #171f2b;
  --surface: #1f2d3d;
  --surface-soft: #25384c;
  --border: #3a5268;
  --text: #f4f7fa;
  --muted: #b7c4cf;
  --accent: #66c0f4;
  --accent-strong: #8bd2fa;
  --focus: #ffffff;
}

* { box-sizing: border-box; }

html {
  background: var(--background);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background:
    radial-gradient(circle at 82% 0%, rgba(102, 192, 244, 0.12), transparent 32rem),
    var(--background);
  color: var(--text);
  font-size: 1rem;
  line-height: 1.68;
}

a { color: var(--accent-strong); text-underline-offset: 0.18em; }
a:hover { color: #ffffff; }
a:focus-visible { border-radius: 0.2rem; outline: 0.2rem solid var(--focus); outline-offset: 0.2rem; }

.shell { margin: 0 auto; max-width: 76rem; padding: 1.25rem; }

.topbar {
  align-items: center;
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: space-between;
  padding: 0.75rem 0 2rem;
}

.brand { color: var(--text); font-size: 1.28rem; font-weight: 800; letter-spacing: -0.025em; text-decoration: none; }
.brand span { color: var(--accent); }
.language { color: var(--muted); font-size: 0.92rem; }
.language a[aria-current="page"] { color: var(--text); font-weight: 700; text-decoration: none; }

.intro {
  border-bottom: 1px solid var(--border);
  max-width: 52rem;
  padding: 2.4rem 0 2.8rem;
}

.eyebrow { color: var(--accent); font-size: 0.82rem; font-weight: 800; letter-spacing: 0.12em; text-transform: uppercase; }
h1 { font-size: clamp(2.25rem, 7vw, 4.6rem); letter-spacing: -0.055em; line-height: 0.98; margin: 0.55rem 0 1.25rem; }
.lead { color: var(--muted); font-size: clamp(1.05rem, 2.5vw, 1.25rem); margin: 0; max-width: 44rem; }
.updated { color: var(--muted); font-size: 0.88rem; margin-top: 1.25rem; }

.layout { display: grid; gap: 2.5rem; grid-template-columns: minmax(0, 1fr); padding: 2.5rem 0 4rem; }
.toc { align-self: start; background: var(--surface); border: 1px solid var(--border); border-radius: 0.7rem; padding: 1.2rem; }
.toc strong { display: block; font-size: 0.92rem; margin-bottom: 0.5rem; }
.toc a { display: block; padding: 0.35rem 0; }
.content { min-width: 0; }
.content section { border-bottom: 1px solid var(--border); padding: 0 0 2rem; margin: 0 0 2rem; scroll-margin-top: 1rem; }
.content section:last-child { border-bottom: 0; }
h2 { font-size: clamp(1.45rem, 3vw, 1.9rem); letter-spacing: -0.025em; line-height: 1.2; margin: 0 0 1rem; }
h3 { font-size: 1.05rem; margin: 1.4rem 0 0.45rem; }
p, ul { margin: 0 0 1rem; }
li + li { margin-top: 0.35rem; }
.summary { background: var(--surface); border-left: 0.22rem solid var(--accent); border-radius: 0.45rem; padding: 1.1rem 1.25rem; }
.contact-card { background: var(--surface-soft); border: 1px solid var(--border); border-radius: 0.7rem; padding: 1.25rem; }
.contact-card p:last-child { margin-bottom: 0; }

.choice-grid { display: grid; gap: 1rem; margin: 3rem auto; max-width: 52rem; }
.choice { background: var(--surface); border: 1px solid var(--border); border-radius: 0.75rem; color: var(--text); display: block; padding: 1.4rem; text-decoration: none; }
.choice:hover { background: var(--surface-soft); border-color: var(--accent); color: var(--text); }
.choice strong { display: block; font-size: 1.15rem; }
.choice span { color: var(--muted); }

footer { border-top: 1px solid var(--border); color: var(--muted); font-size: 0.9rem; padding: 1.5rem 0 2.5rem; }

@media (min-width: 54rem) {
  .shell { padding-left: 2rem; padding-right: 2rem; }
  .layout { grid-template-columns: 15rem minmax(0, 1fr); }
  .toc { position: sticky; top: 1.25rem; }
  .choice-grid { grid-template-columns: 1fr 1fr; }
}

@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }