:root { --nen: #fbfaf7; --chu: #1d1d1b; --phu: #6b6a64; --vien: #d9d6cc; --chinh: #1f4e79; --canh: #8a1c1c;
  --canh-nen: #fbeaea; --tro-ly: #f3efe2; }
@media (prefers-color-scheme: dark) {
  :root { --nen: #161614; --chu: #ecebe6; --phu: #a3a198; --vien: #3a3934; --chinh: #8fb8e0; --canh: #f2a3a3;
    --canh-nen: #3a1d1d; --tro-ly: #2a2820; }
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--nen); color: var(--chu); font: 16px/1.5 system-ui, -apple-system, "Segoe UI",
  Roboto, sans-serif; }
main, header { max-width: 760px; margin: 0 auto; padding: 16px; }
header { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; border-bottom: 1px solid var(--vien); }
header form { margin-left: auto; }
h1 { font-size: 1.5rem; margin: 8px 0 12px; }
h2 { font-size: 1.15rem; margin: 20px 0 8px; }
h3 { font-size: 1rem; margin: 14px 0 6px; color: var(--phu); }
a { color: var(--chinh); }
button { font: inherit; padding: 10px 16px; border-radius: 8px; border: 1px solid var(--vien); background: transparent;
  color: var(--chu); cursor: pointer; }
button.chinh { background: var(--chinh); color: var(--nen); border-color: var(--chinh); width: 100%; margin: 12px 0; }
button:disabled { opacity: .5; cursor: default; }
label { display: block; margin: 12px 0 4px; }
label.hang { display: flex; gap: 8px; align-items: flex-start; }
input[type=text], input[type=tel], input[type=email], input[type=number] { display: block; width: 100%; font: inherit;
  padding: 10px; margin-top: 4px; border-radius: 8px; border: 1px solid var(--vien); background: transparent;
  color: var(--chu); }
.phu { color: var(--phu); font-size: .9rem; }
.mo { color: var(--phu); }
.bao { min-height: 1.5em; }
.bao.loi, .canh { color: var(--canh); }
.canh { background: var(--canh-nen); padding: 8px 12px; border-radius: 8px; }
.kiem { font-size: 1.05rem; }
.tu-kiem { font-weight: 700; letter-spacing: .06em; }
.tu-kiem.lon { font-size: 1.6rem; }
.tro-ly { background: var(--tro-ly); padding: 8px 12px; border-radius: 8px; }
.nguyen { white-space: pre-wrap; overflow-wrap: anywhere; }
.ds { list-style: none; padding: 0; }
.the { border: 1px solid var(--vien); border-radius: 8px; padding: 10px 12px; margin: 8px 0; }
table { border-collapse: collapse; width: 100%; }
th, td { text-align: left; vertical-align: top; padding: 4px 6px; border-bottom: 1px solid var(--vien);
  overflow-wrap: anywhere; }
tr.doi td { font-weight: 600; }
.doi-bang th:first-child { width: 28%; }
.ma { font: 700 2.2rem/1.2 ui-monospace, "SF Mono", Menlo, monospace; letter-spacing: .12em; }
form.nho { display: inline; }
details { margin: 12px 0; }