:root {
  --nen: #f6f7f9;
  --the: #ffffff;
  --chu: #1b2430;
  --chu-phu: #5a6574;
  --vien: #d9dee6;
  --nhan: #1f3a5f;
  --nhan-nen: #e8eef7;
  --word: #1d5fb4;
  --excel: #1e7a46;
  --chung: #5a5f6b;
  --nhan-chu: #ffffff;
}
@media (prefers-color-scheme: dark) {
  :root {
    --nen: #12161c;
    --the: #1b212a;
    --chu: #e8ecf2;
    --chu-phu: #a3adbb;
    --vien: #2c3542;
    --nhan: #8fb4ec;
    --nhan-nen: #1f2a3b;
    --word: #5b9bf0;
    --excel: #4cc38a;
    --chung: #9aa3b2;
    --nhan-chu: #0b1018;
  }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--nen);
  color: var(--chu);
  font: 17px/1.55 system-ui, "Segoe UI", Roboto, sans-serif;
}
.gioi-han { max-width: 820px; margin: 0 auto; padding: 0 16px; }
.an { position: absolute; left: -9999px; }
a { color: var(--nhan); }
:focus-visible { outline: 3px solid var(--nhan); outline-offset: 2px; }

.dau { background: var(--the); border-bottom: 1px solid var(--vien); padding: 14px 0 16px; position: sticky; top: 0; z-index: 5; }
.ten { font-size: 1.35rem; font-weight: 700; text-decoration: none; color: var(--chu); }
.phu { margin: 2px 0 10px; color: var(--chu-phu); font-size: .9rem; text-wrap: balance; }
.tim input {
  width: 100%;
  font: inherit;
  padding: 12px 14px;
  border: 2px solid var(--vien);
  border-radius: 10px;
  background: var(--nen);
  color: var(--chu);
}
.tim input:focus { border-color: var(--nhan); outline: none; }

main { padding-top: 18px; padding-bottom: 32px; min-height: 60vh; }
.tieu-muc { font-size: 1.15rem; margin: 22px 0 10px; text-wrap: balance; }
.luoi { display: grid; grid-template-columns: repeat(2, 1fr); gap: 10px; }
.o-viec {
  display: flex; flex-direction: column; gap: 4px;
  background: var(--the); border: 1px solid var(--vien); border-radius: 12px;
  padding: 16px; text-decoration: none; color: var(--chu); min-height: 92px;
}
.o-viec strong { font-size: 1.05rem; color: var(--nhan); }
.o-viec span { font-size: .88rem; color: var(--chu-phu); }
.o-viec:hover, .the:hover { border-color: var(--nhan); }

.meo { background: var(--nhan-nen); border-radius: 12px; padding: 14px 16px; margin-top: 16px; }
.meo h2 { margin: 0 0 6px; font-size: .95rem; color: var(--chu-phu); font-weight: 600; }
.meo p { margin: 6px 0 0; }
kbd {
  font: 600 1rem ui-monospace, Consolas, monospace;
  background: var(--the); border: 1px solid var(--vien); border-bottom-width: 3px;
  border-radius: 6px; padding: 2px 8px;
}

.ds { display: grid; gap: 10px; }
.the {
  display: block; background: var(--the); border: 1px solid var(--vien); border-radius: 12px;
  padding: 14px 16px; text-decoration: none; color: var(--chu);
}
.the h3 { margin: 6px 0 4px; font-size: 1.05rem; text-wrap: balance; }
.the p { margin: 0; color: var(--chu-phu); font-size: .93rem; }
.nhan {
  display: inline-block; font-size: .75rem; font-weight: 700; letter-spacing: .03em;
  padding: 2px 9px; border-radius: 99px; color: var(--nhan-chu);
}
.nhan-word { background: var(--word); }
.nhan-excel { background: var(--excel); }
.nhan-chung { background: var(--chung); }
.vi-du { font-family: ui-monospace, Consolas, monospace; overflow-wrap: anywhere; }

.ve { display: inline-block; margin-bottom: 6px; }
.bai { background: var(--the); border: 1px solid var(--vien); border-radius: 14px; padding: 18px 18px 8px; }
.bai h2 { margin: 8px 0 12px; font-size: 1.3rem; line-height: 1.3; text-wrap: balance; }
.bai h3 { margin: 22px 0 8px; font-size: 1.05rem; color: var(--nhan); }
.nhanh { background: var(--nhan-nen); border-radius: 10px; padding: 4px 16px 14px; }
.nhanh h3 { margin-top: 12px; }
.nhanh p { margin: 0; font-weight: 500; }
.hanh { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin-top: 12px; }
code { font: .92rem ui-monospace, Consolas, monospace; background: var(--the); border: 1px solid var(--vien); border-radius: 6px; padding: 4px 8px; overflow-wrap: anywhere; }
.nut-chep {
  font: inherit; font-size: .9rem; cursor: pointer; padding: 8px 14px; border-radius: 8px;
  border: 1px solid var(--nhan); background: var(--the); color: var(--nhan); min-height: 40px;
}
.buoc { padding-left: 0; list-style: none; counter-reset: b; margin: 0; }
.buoc li { counter-increment: b; position: relative; padding: 0 0 14px 42px; }
.buoc li::before {
  content: counter(b); position: absolute; left: 0; top: 0; width: 30px; height: 30px; border-radius: 50%;
  background: var(--nhan); color: var(--nhan-chu); display: grid; place-items: center; font-weight: 700; font-size: .9rem;
}
.buoc p { margin: 2px 0 8px; }
.bai > img { display: block; width: 100%; height: auto; border: 1px solid var(--vien); border-radius: 10px; margin: 0 0 14px; background: #fff; }
.buoc img { max-width: 100%; height: auto; border: 1px solid var(--vien); border-radius: 8px; }
.bai ul { padding-left: 20px; margin: 0; }
.bai li { margin-bottom: 6px; }
.can { font-size: .85rem; color: var(--chu-phu); border-top: 1px solid var(--vien); padding-top: 10px; }
.trong { color: var(--chu-phu); }
.chan { padding-top: 12px; padding-bottom: 28px; font-size: .82rem; color: var(--chu-phu); }

.gap { display: grid; gap: 10px; }
.the-gap { display: block; background: var(--the); border: 1px solid var(--vien); border-radius: 12px; overflow: hidden; text-decoration: none; color: var(--chu); }
.the-gap:hover { border-color: var(--nhan); }
.the-gap img { display: block; width: 100%; height: auto; background: #fff; }
.the-gap span { display: block; padding: 10px 14px 12px; font-weight: 600; text-wrap: balance; }

@media (min-width: 620px) {
  .gap { grid-template-columns: repeat(2, 1fr); }
  .luoi { grid-template-columns: repeat(4, 1fr); }
  .bai { padding: 24px 28px 12px; }
}
@media print {
  .dau, .chan, .nut-chep, .ve { display: none; }
  body { background: #fff; color: #000; font-size: 12pt; }
  .bai { border: 0; padding: 0; }
}