/* ===== STU - Nhập môn Web: CSS dùng chung ===== */
:root {
  --do: #c0151b;
  --do-dam: #a51217;
  --xanh: #1b7f3a;
  --nen: #fff6f2;
  --chu: #222;
  --xam: #666;
  --vien: #e9e9e9;
}

* {
  box-sizing: border-box
}

html {
  scroll-behavior: smooth
}

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background: var(--nen);
  color: var(--chu);
  line-height: 1.6;
}

a {
  color: inherit;
  text-decoration: none
}

img {
  max-width: 100%;
  height: auto;
  display: block
}

.container {
  width: 92%;
  max-width: 1000px;
  margin: 0 auto;
}

header {
  background: var(--do);
  color: #fff;
  padding: 14px 0;
}

.header-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}

header h1 {
  margin: 0;
  font-size: 22px
}

header p {
  margin: 4px 0 0;
  font-size: 13px;
  opacity: .95
}

.btn {
  display: inline-block;
  padding: 10px 14px;
  background: #fff;
  color: var(--do);
  border-radius: 6px;
  font-weight: bold;
}

nav {
  background: var(--do-dam)
}

nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
}

nav a {
  display: block;
  padding: 10px 12px;
  color: #fff;
  font-weight: bold;
  font-size: 14px;
}

nav a:hover,
nav a.active {
  background: var(--xanh)
}

.banner {
  background: linear-gradient(90deg, rgba(192, 21, 27, .95), rgba(27, 127, 58, .90));
  color: #fff;
  padding: 18px 0;
}

.banner .box {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  flex-wrap: wrap;
}

.banner h2 {
  margin: 0;
  font-size: 26px;
  color: #000;
  background: #ffffffcc;
  /* nền trắng mờ */
  display: inline-block;
  padding: 6px 10px;
  border-radius: 6px;
}

.banner .tag {
  margin-top: 6px;
  font-size: 14px;
  opacity: .95
}

.banner .mini {
  font-size: 13px;
  opacity: .95;
  margin-top: 6px
}

.section {
  padding: 16px 0
}

.section h2 {
  margin: 0 0 10px;
  color: var(--do);
  border-left: 5px solid var(--do);
  padding-left: 10px;
  font-size: 20px;
}

.section h3 {
  margin: 10px 0 6px;
  color: var(--xanh);
  font-size: 16px
}

.grid3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px
}

.grid2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px
}

.card {
  background: #fff;
  border: 1px solid var(--vien);
  border-radius: 8px;
  overflow: hidden;
}

.card .pad {
  padding: 10px 12px
}

.card h3 {
  margin: 0 0 6px;
  color: var(--xanh);
  font-size: 16px
}

.card p {
  margin: 0;
  color: var(--xam);
  font-size: 14px
}

.badge {
  display: inline-block;
  padding: 4px 8px;
  border-radius: 999px;
  background: #ffe3e1;
  color: var(--do);
  font-size: 12px;
  font-weight: bold;
}

.note {
  background: #fff;
  border: 1px dashed var(--xanh);
  padding: 10px 12px;
  border-radius: 8px;
  color: #1f2937;
}

.gallery {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px
}

.figure {
  background: #fff;
  border: 1px solid var(--vien);
  border-radius: 8px;
  overflow: hidden
}

.figure .cap {
  padding: 8px 10px;
  font-size: 13px;
  color: var(--xam)
}

table {
  width: 100%;
  border-collapse: collapse;
  background: #fff;
  border: 1px solid var(--vien);
  border-radius: 8px;
  overflow: hidden
}

th,
td {
  border: 1px solid var(--vien);
  padding: 8px 10px;
  text-align: left;
  font-size: 14px
}

th {
  background: #ffe3e1;
  color: var(--do)
}

.form {
  background: #fff;
  border: 1px solid var(--vien);
  border-radius: 8px;
  padding: 12px
}

.input {
  margin-bottom: 10px
}

label {
  display: block;
  font-weight: bold;
  margin-bottom: 6px
}

input,
textarea {
  width: 100%;
  padding: 10px;
  border: 1px solid #ddd;
  border-radius: 6px;
  font-family: inherit;
  font-size: 14px;
}

button {
  padding: 10px 14px;
  background: var(--do);
  color: #fff;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  font-weight: bold;
}

button:hover {
  opacity: .92
}

.embed {
  width: 100%;
  aspect-ratio: 9/16;
  /* shorts */
  border: 1px solid var(--vien);
  border-radius: 8px;
  overflow: hidden;
  background: #000;
}

footer {
  margin-top: 18px;
  background: #111;
  color: #fff;
  padding: 14px 0;
  font-size: 14px;
}

footer a {
  color: #fff;
  text-decoration: underline
}

small.muted {
  color: #d1d5db
}

@media(max-width:820px) {
  .grid3 {
    grid-template-columns: 1fr
  }

  .grid2 {
    grid-template-columns: 1fr
  }

  .gallery {
    grid-template-columns: 1fr
  }
}


/* FIX card equal height */
.grid3,
.grid2 {
  align-items: stretch
}

.card {
  display: flex;
  flex-direction: column
}

.card img {
  height: 220px;
  object-fit: cover
}

/* FIX video responsive */
.video-wrap {
  position: relative;
  padding-top: 56.25%
}

.video-wrap iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}