/* ===== Base (mobile-first) ===== */
:root {
  --bg: #fafafa;
  --fg: #222;
  --muted: #555;
  --brand: #007acc;
  --radius: 10px;
}

* { box-sizing: border-box; }

html, body {
  height: 100%;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  /* Fluid type: 16px on small, up to 18px on large */
  font-size: clamp(16px, 1.8vw, 18px);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* ===== Header / Hero ===== */
header {
  text-align: center;
  padding: 24px 16px 16px;
  background: #fff;
  box-shadow: 0 1px 4px rgba(0,0,0,.06);
}

header img {
  /* shrink a bit on phones, never overflow */
  width: 60vw;
  max-width: 220px;
  height: auto;
  margin: 0 auto 12px;
  display: block;
  border-radius: var(--radius);
}

h1 {
  margin: 8px 0 6px;
  font-size: clamp(22px, 5.5vw, 30px);
  line-height: 1.25;
}

p.tagline {
  margin: 0;
  color: var(--muted);
  font-size: clamp(14px, 3.8vw, 18px);
}

/* CTA = full width on mobile for easier tapping */
.cta {
  display: block;
  width: 100%;
  max-width: 480px;
  margin: 14px auto 0;
  padding: 14px 16px;
  background: var(--brand);
  color: #fff;
  text-decoration: none;
  border-radius: 8px;
  font-weight: 600;
  text-align: center;
  box-shadow: 0 2px 8px rgba(0,122,204,.18);
}
.cta:focus-visible { outline: 2px solid #111; outline-offset: 2px; }

/* ===== Main content ===== */
main {
  max-width: 860px;
  margin: 24px auto;
  padding: 0 16px;
}

h2 { 
  margin: 0 0 10px;
  font-size: clamp(18px, 4.2vw, 24px);
}
h3 {
  margin: 8px 0 4px;
  font-size: clamp(16px, 3.8vw, 20px);
}

/* ===== Authors section ===== */
section.authors {
  display: grid;
  grid-template-columns: 1fr;     /* stack on phones */
  gap: 18px;
  margin-top: 22px;
}

.author {
  text-align: center;
  padding: 16px;
  background: #fff;
  border-radius: var(--radius);
  box-shadow: 0 1px 4px rgba(0,0,0,.06);
}

.author img {
  width: 112px;
  height: 112px;
  border-radius: 50%;
  object-fit: cover;
  display: block;
  margin: 0 auto 8px;
}

.author p {
  margin: 6px 0 0;
  color: #333;
}

/* Social icons: larger, comfy spacing */
.social {
  display: flex;
  justify-content: center;
  gap: 18px;
  margin-top: 10px;
}

.social a {
  display: inline-flex;
  padding: 8px;                 /* bigger tap target */
  border-radius: 50%;
}

.social a svg {
  width: 26px;
  height: 26px;
  fill: #0077b5;                /* LinkedIn default */
  transition: transform .15s ease, opacity .15s ease;
}
.social a.youtube svg { fill: #ff0000; }
.social a:hover svg { transform: translateY(-1px); opacity: .9; }
.social a:focus-visible { outline: 2px solid #111; outline-offset: 2px; }

/* ===== Footer ===== */
footer {
  text-align: center;
  padding: 24px 16px 40px;
  color: #666;
  font-size: 0.95rem;
}

/* ===== Tablet+ tweaks ===== */
@media (min-width: 640px) {
  header { padding: 40px 20px 24px; }
  .cta { display: inline-block; width: auto; padding: 12px 18px; }
  section.authors {
    grid-template-columns: repeat(2, minmax(260px, 1fr)); /* 2 columns */
    gap: 22px;
  }
}

/* ===== Desktop+ ===== */
@media (min-width: 1024px) {
  header img { max-width: 240px; }
  main { margin: 36px auto; }
  section.authors { gap: 26px; }
}