:root {
  --bg: #f6f7f9; --card: #fff; --text: #1d2330; --muted: #677085; --line: #dfe3ea;
  --accent: #1f6feb; --accent-text: #fff; --ok: #1a7f37; --warn: #9a6700; --bad: #cf222e;
  --ok-bg: #dafbe1; --warn-bg: #fff8c5; --bad-bg: #ffebe9;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1218; --card: #171b23; --text: #e6e9ef; --muted: #9aa3b5; --line: #2a303c;
    --accent: #4c8dff; --accent-text: #0b0e13; --ok: #4ac26b; --warn: #d4a72c; --bad: #ff7b72;
    --ok-bg: #12301c; --warn-bg: #33290b; --bad-bg: #3b1616;
    color-scheme: dark;
  }
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text); font: 15px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; }
main { max-width: 980px; margin: 0 auto; padding: 16px; }
body.narrow main { max-width: 440px; padding-top: 48px; }
h1 { font-size: 22px; margin: 0 0 12px; }
h2 { font-size: 18px; margin: 20px 0 8px; }
a { color: var(--accent); }
code { font-size: 13px; background: var(--line); padding: 1px 5px; border-radius: 4px; word-break: break-all; }
.muted { color: var(--muted); }
.err { color: var(--bad); background: var(--bad-bg); padding: 8px 10px; border-radius: 6px; }
p.ok { color: var(--ok); background: var(--ok-bg); padding: 8px 10px; border-radius: 6px; }
.top { display: flex; justify-content: space-between; align-items: center; padding: 10px 16px; background: var(--card); border-bottom: 1px solid var(--line); }
.top form { margin: 0; }
.brand { font-weight: 600; color: var(--text); text-decoration: none; }
label { display: block; margin: 10px 0; font-weight: 500; }
label small { font-weight: 400; color: var(--muted); }
input, select, textarea { display: block; width: 100%; margin-top: 4px; padding: 8px 10px; font: inherit; color: var(--text); background: var(--card); border: 1px solid var(--line); border-radius: 6px; }
textarea { min-height: 90px; resize: vertical; }
textarea.big { min-height: 360px; font-family: ui-monospace, Menlo, monospace; font-size: 13px; }
button, .btn { display: inline-block; padding: 8px 14px; font: inherit; font-weight: 500; border-radius: 6px; border: 1px solid var(--accent); background: var(--accent); color: var(--accent-text); cursor: pointer; text-decoration: none; }
button.secondary, .btn.secondary { background: var(--card); color: var(--text); border-color: var(--line); }
button.danger { background: var(--card); color: var(--bad); border-color: var(--bad); }
button.link { background: none; border: none; color: var(--accent); padding: 4px; }
button:disabled { opacity: .5; cursor: wait; }
[hidden] { display: none !important; }
form button { margin-top: 6px; }
.row { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 12px; }
.card { background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 14px; }
section > .card + .card { margin-top: 14px; }
.danger-zone { border-color: var(--bad); }
.danger-zone h2 { color: var(--bad); }
.head { display: flex; justify-content: space-between; align-items: center; gap: 12px; margin-bottom: 12px; }
.head h1 { margin: 0; }
.head-actions { display: flex; flex-wrap: wrap; gap: 8px; justify-content: flex-end; }
a.card { display: block; color: var(--text); text-decoration: none; }
a.card:hover { border-color: var(--accent); }
.card h3 { margin: 0 0 6px; font-size: 17px; }
.kv { display: grid; grid-template-columns: auto 1fr; gap: 2px 12px; font-size: 14px; }
.kv dt { color: var(--muted); }
.kv dd { margin: 0; }
.badge { display: inline-block; font-size: 12px; font-weight: 600; padding: 1px 8px; border-radius: 99px; background: var(--line); color: var(--text); }
.badge.ok { background: var(--ok-bg); color: var(--ok); }
.badge.warn { background: var(--warn-bg); color: var(--warn); }
.badge.bad { background: var(--bad-bg); color: var(--bad); }
.banner { background: var(--warn-bg); color: var(--warn); border-radius: 8px; padding: 10px 12px; margin: 12px 0; }
.tabs { display: flex; gap: 4px; overflow-x: auto; border-bottom: 1px solid var(--line); margin: 16px 0 12px; }
.tabs a { padding: 8px 12px; white-space: nowrap; color: var(--muted); text-decoration: none; border-bottom: 2px solid transparent; }
.tabs a.on { color: var(--text); border-color: var(--accent); font-weight: 600; }
table { width: 100%; border-collapse: collapse; font-size: 14px; }
th, td { text-align: left; padding: 6px 8px; border-bottom: 1px solid var(--line); vertical-align: top; }
td input, td textarea { margin: 0; }
.scroll { overflow-x: auto; }
.avatar { width: 160px; height: 160px; object-fit: cover; border-radius: 50%; border: 1px solid var(--line); }
.qr svg, .qr img { width: 240px; height: 240px; background: #fff; padding: 8px; border-radius: 8px; }
.note { white-space: pre-wrap; background: var(--bg); border-radius: 6px; padding: 8px 10px; font-size: 14px; }
.total { margin-top: 14px; font-weight: 600; }
#toast { position: fixed; left: 50%; bottom: 20px; transform: translateX(-50%); max-width: 92vw; padding: 10px 16px; border-radius: 8px; background: var(--text); color: var(--bg); z-index: 9; white-space: pre-wrap; }
#toast.bad { background: var(--bad); color: #fff; }
@media (max-width: 600px) {
  .hide-sm { display: none; }
  th, td { padding: 6px 4px; }
  /* Người quen: one card per person instead of a cramped table. */
  .people thead { display: none; }
  .people tr { display: block; border: 1px solid var(--line); border-radius: 8px; padding: 8px 10px; margin-bottom: 10px; }
  .people td { display: block; border: 0; padding: 3px 0; }
  .people td[data-label]::before { content: attr(data-label); display: block; font-size: 12px; color: var(--muted); }
}