/* Global Theme Variables */
:root {
  --bg-grad-start: #f8fafc;
  --bg-grad-end: #ffffff;
  --text: #111827;
  --muted: #6b7280;
  --surface: #ffffff;
  --border: #e5e7eb;
  --brand: #0ea5e9;
  --brand-dark: #0284c7;
}

/* Base */
* { box-sizing: border-box; }

body {
  background: linear-gradient(to bottom, var(--bg-grad-start), var(--bg-grad-end));
  font-family: "Inter", system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  color: var(--text);
  line-height: 1.6;
}

.container { max-width: 1100px; margin: 0 auto; padding: 0 1rem; }

/* Header */
header { background-color: #111827; color: white; }
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem 0;
}
.headshot {
  width: 75px;
  height: 75px;
  border-radius: 50%;
  object-fit: cover;
  margin-right: 12px;
  border: 2px solid white;
  background-color: #e5e7eb; /* subtle placeholder bg */
}

h1 { font-size: 1.5rem; font-weight: 700; margin: 0; }

nav { display: flex; flex-wrap: wrap; gap: .75rem; }
nav a {
  color: white;
  text-decoration: none;
  padding: .4rem .7rem;
  border-radius: .5rem;
  font-size: 1rem;
  transition: background-color .2s ease, color .2s ease;
}
nav a:hover { background-color: rgba(255,255,255,0.1); }

@media (max-width: 640px) {
  .header-inner { flex-direction: column; align-items: center; }
  nav { justify-content: center; }
}

/* Header brand group replaces inline flex */
.brand-group { display: flex; align-items: center; gap: .75rem; }

/* Layout */
main { padding: 2rem; flex: 1; }
footer { background-color: #333; color: white; text-align: center; padding: 1rem; margin-top: auto; }

/* Home Intro */
.intro {
  background: linear-gradient(135deg, #f8f9fa, #ffffff);
  padding: 2.5rem;
  border-bottom: 3px solid #ccc;
  margin-bottom: 2rem;
  text-align: center;
  border-radius: 12px;
  box-shadow: 0px 4px 8px rgba(0, 0, 0, 0.1);
  max-width: 750px;
  margin-left: auto;
  margin-right: auto;
}
.intro h2 { color: #333; font-weight: 700; font-size: 1.8rem; margin-bottom: 1rem; }
.intro p { color: #555; font-size: 1.1rem; line-height: 1.6; }
.intro ul { padding-left: 20px; list-style-type: disc; list-style-position: inside; }
.intro ul li { margin-bottom: .5rem; font-size: 1.1rem; }

/* Cards (home/projects/blog) */
.cards { display: flex; flex-wrap: wrap; justify-content: center; gap: 1rem; padding: 1rem; }
.card {
  border-radius: 12px;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  text-decoration: none;
  color: #333;
  width: 250px;
  padding: 1.5rem;
  text-align: center;
  font-weight: bold;
  transition: transform 0.2s, box-shadow 0.2s, filter 0.2s;
  background: #f4f4f4;
}
.card:hover { transform: scale(1.05); box-shadow: 0 4px 8px rgba(0,0,0,0.2); filter: brightness(0.98); }
/* Home main cards hues */
.card:nth-child(1) { background: #E3F2FD; }
.card:nth-child(2) { background: #FFEBEE; }
.card:nth-child(3) { background: #E8F5E9; }
.card:nth-child(4) { background: #FFFDE7; }

/* Projects specific */
.card-img {
  width: 100%;
  height: 150px; /* normalize thumbnail height for consistent layout */
  object-fit: contain;
  object-position: center;
  display: block;
  border-radius: 8px;
}

/* Blog cards */
.card h3 { margin-top: 0; margin-bottom: .5rem; }
.card h4 { margin: 0 0 .75rem; color: var(--muted); font-weight: 600; }
.card p { font-size: .95rem; line-height: 1.4; margin: 0; }

/* Section titles */
.section-title { text-align: center; font-size: 1.6rem; margin: 2.5rem 0 .5rem; }
.section-subtitle { text-align: center; color: var(--muted); margin: 0 0 1.5rem; }

/* QR Codes (home) */
.qr-section { padding: 0 1rem 2.5rem; }
.qr-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 1rem; max-width: 900px; margin: 0 auto; }
.qr-card { background: var(--surface); border: 1px solid var(--border); border-radius: 12px; box-shadow: 0 1px 2px rgba(0,0,0,0.04); padding: 1rem; text-align: center; transition: transform .2s, box-shadow .2s, filter .2s; }
.qr-card:hover { transform: scale(1.05); box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2); filter: brightness(0.98); }
.qr-card img { width: 100%; height: auto; aspect-ratio: 1 / 1; object-fit: contain; image-rendering: crisp-edges; }
.qr-card a { display: block; border-radius: 10px; }
.qr-card a:focus-visible { outline: 3px solid var(--brand); outline-offset: 4px; }
.qr-card figcaption { margin-top: .6rem; color: var(--muted); font-weight: 600; }

/* About page */
.bio { background: linear-gradient(135deg, #f8f9fa, #ffffff); padding: 2rem; border-bottom: 2px solid #ddd; margin-bottom: 2rem; border-radius: 12px; }
.bio h2 { font-size: 2rem; margin-bottom: 1rem; text-align: center; }

/* Publications page */
section details { margin-bottom: 1.5rem; }
section h3 { margin-top: 2rem; margin-bottom: 1rem; border-bottom: 1px solid #ddd; padding-bottom: .5rem; }

/* Publications: alternating card colors for readability */
.pub-list details {
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1rem 1.25rem;
  background: var(--surface);
}
.pub-list details:nth-of-type(4n+1) { background: #E3F2FD; }
.pub-list details:nth-of-type(4n+2) { background: #FFEBEE; }
.pub-list details:nth-of-type(4n+3) { background: #E8F5E9; }
.pub-list details:nth-of-type(4n+4) { background: #FFFDE7; }
.pub-list summary { font-weight: 600; cursor: pointer; }

/* Project/Blog detail nav */
.project-navigation { display: flex; justify-content: space-between; margin-top: 40px; padding-top: 20px; border-top: 1px solid #ccc; }
.project-navigation a { text-decoration: none; font-size: 1.2rem; color: var(--brand); transition: color .2s ease; }
.project-navigation a:hover { color: var(--brand-dark); }

/* Utilities */
img { max-width: 100%; height: auto; }
.equation { font-family: Menlo, Consolas, "Courier New", monospace; background: #f5f5f5; padding: .5em 1em; margin: 1em 0; text-align: center; border-radius: 4px; }

/* Content images (replaces inline styles) */
.content-image { max-width: 100%; height: auto; border-radius: 8px; margin-top: 1rem; display: block; }