:root {
  /* Dark mode mặc định */
  --bg: #0b0c10;
  --panel: #0f172a;
  --text: #e5e7eb;
  --muted: #94a3b8;
  --brand: #0ea5e9;
  --ring: rgba(14,165,233,.35);
  --card: #0b1220;
}

/* Tự động theo hệ điều hành */
@media (prefers-color-scheme: light) {
  :root {
    --bg: #f8fafc;
    --panel: #ffffff;
    --text: #0f172a;
    --muted: #475569;
    --brand: #0ea5e9;
    --ring: rgba(14,165,233,.25);
    --card: #f1f5f9;
  }
}

/* Nếu user chọn override */
body[data-theme="dark"] {
  --bg: #0b0c10;
  --panel: #0f172a;
  --text: #e5e7eb;
  --muted: #94a3b8;
  --brand: #0ea5e9;
  --ring: rgba(14,165,233,.35);
  --card: #0b1220;
}
body[data-theme="light"] {
  --bg: #f8fafc;
  --panel: #ffffff;
  --text: #0f172a;
  --muted: #475569;
  --brand: #0ea5e9;
  --ring: rgba(14,165,233,.25);
  --card: #f1f5f9;
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  padding-top: 72px; /* đúng bằng chiều cao header */
  font: 16px/1.6 system-ui, -apple-system, Segoe UI, Roboto, Inter, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
}
a { color: var(--brand); text-decoration: none; }
a:hover { text-decoration: underline; }

.container { max-width: 1100px; margin: 0 auto; padding: 24px; }

/* Header */
header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 100;
  backdrop-filter: saturate(180%) blur(8px);
  background: color-mix(in oklab, var(--bg) 86%, transparent);
  border-bottom: 1px solid color-mix(in oklab, var(--text) 12%, transparent);
}

header .inner {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 12px 24px;
}
.avatar {
  width: 48px; height: 48px; border-radius: 50%;
  object-fit: cover;
  border: 2px solid color-mix(in oklab, var(--brand) 50%, transparent);
}
.brand { display: flex; flex-direction: column; }
.brand h1 { font-size: 18px; margin: 0; }
.brand span { font-size: 13px; color: var(--muted); }
.nav { margin-left: auto; display: flex; gap: 14px; align-items: center; }
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 10px 14px; border-radius: 16px;
  border: 1px solid color-mix(in oklab, var(--text) 12%, transparent);
  background: linear-gradient(180deg, color-mix(in oklab, var(--panel) 70%, transparent), var(--panel));
  box-shadow: 0 1px 0 color-mix(in oklab, #000 15%, transparent) inset;
  color: var(--text);
}
.btn:hover { box-shadow: 0 0 0 3px var(--ring); }

/* Hero */
.hero {
  display: grid;
  grid-template-columns: 1.2fr .8fr;
  gap: 24px;
  margin-top: 28px;
}
.hero .card {
  background: var(--panel);
  border: 1px solid color-mix(in oklab, var(--text) 12%, transparent);
  border-radius: 24px;
  padding: 24px;
}
.hero h2 { font-size: 32px; line-height: 1.2; margin: 0 0 12px; }
.hero p { margin: 0 0 16px; color: var(--muted); }
.tags { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 12px; }
.tag {
  padding: 6px 10px;
  border-radius: 12px;
  background: var(--card);
  border: 1px solid color-mix(in oklab, var(--text) 10%, transparent);
  font-size: 13px;
}

/* Grid */
.grid { display: grid; grid-template-columns: repeat(12,1fr); gap: 24px; margin-top: 28px; }
.col-8 { grid-column: span 8; }
.col-4 { grid-column: span 4; }
.col-12 { grid-column: span 12; }
.section {
  background: var(--panel);
  border: 1px solid color-mix(in oklab, var(--text) 12%, transparent);
  border-radius: 24px;
  padding: 24px;
}
.section h3 { margin: 0 0 14px; font-size: 20px; }

/* Timeline */
.timeline { position: relative; margin: 0; padding: 0; list-style: none; }
.timeline::before {
  content:""; position: absolute; left: 10px; top: 0; bottom: 0;
  width: 2px; background: color-mix(in oklab, var(--text) 12%, transparent);
}
.timeline li {
  position: relative; padding-left: 32px; margin: 16px 0;
}
.timeline li::marker { content:""; }
.timeline li::before {
  content:""; position: absolute; left: 3px; top: 6px;
  width: 14px; height: 14px; border-radius: 50%;
  background: var(--brand); box-shadow: 0 0 0 3px var(--ring);
}
.role { display: flex; justify-content: space-between; gap: 12px; }
.role strong { font-size: 16px; }
.role span { color: var(--muted); font-size: 14px; }

/* Project cards */
.cards { display: grid; grid-template-columns: repeat(auto-fill,minmax(240px,1fr)); gap: 16px; }
.card {
  background: var(--panel);
  border: 1px solid color-mix(in oklab, var(--text) 12%, transparent);
  border-radius: 20px;
  padding: 16px;
  display: flex; flex-direction: column; gap: 10px;
}
.card img { width: 100%; height: 140px; object-fit: cover; border-radius: 12px; }
.card h4 { margin: 0; font-size: 16px; }
.card p { margin: 0; color: var(--muted); font-size: 14px; }
.card .links { display: flex; justify-content: center; gap: 10px; margin-top: auto; }

/* Contact */
form { display: grid; gap: 12px; }
input, textarea {
  width: 100%; padding: 12px 14px; border-radius: 14px;
  border: 1px solid color-mix(in oklab, var(--text) 12%, transparent);
  background: var(--panel); color: var(--text);
}
textarea { min-height: 120px; resize: vertical; }
label { font-size: 14px; color: var(--muted); }
.note { color: var(--muted); font-size: 13px; }

/* Footer */
footer { margin: 28px 0 40px; color: var(--muted); text-align: center; }

/* Responsive */
@media (max-width: 900px) {
  .hero { grid-template-columns: 1fr; }
  .col-8, .col-4, .col-12 { grid-column: span 12; }
  .nav { display: none; }
}

/* Đảm bảo ảnh trong bài viết không bị tràn */
article img {
  max-width: 100%;
  height: auto;
  display: block;
  margin: 16px auto; /* căn giữa và có khoảng cách */
  border-radius: 12px; /* bo góc giống demo */
}

/* Nội dung bài viết luôn wrap, không cho cuộn ngang */
.section.col-12,
.section.col-12 * {
  white-space: normal !important;
  word-wrap: break-word;
  overflow-wrap: break-word;
  word-break: break-word;
}

/* Code block vẫn giữ format nhưng sẽ xuống dòng khi dài */
.section.col-12 code,
.section.col-12 pre {
  white-space: pre-wrap !important;
  word-break: break-word;
}