/* =========================================================
   BASE - Reset, Typography, Layout, Accessibility
   ========================================================= */

*,
*::before,
*::after {
	box-sizing: border-box;
}

html {
	-webkit-text-size-adjust: 100%;
	scroll-behavior: smooth;
}

body {
	margin: 0;
	font-family: var(--font-primary);
	font-size: var(--font-size-base);
	line-height: var(--line-height-base);
	color: var(--color-text);
	background-color: var(--color-bg);
}

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

a {
	color: var(--color-primary);
	text-decoration: none;
	transition: color var(--transition-fast);
}

a:hover {
	color: var(--color-primary-dark);
}

h1, h2, h3, h4, h5, h6 {
	margin: 0 0 16px;
	font-weight: 700;
	line-height: 1.3;
}

h1 { font-size: clamp(28px, 4vw, 44px); }
h2 { font-size: clamp(22px, 3vw, 32px); }
h3 { font-size: 20px; }
h4 { font-size: 18px; }

p { margin: 0 0 16px; }

ul, ol { margin: 0; padding: 0; list-style: none; }

button, input, select, textarea {
	font-family: inherit;
	font-size: inherit;
}

/* Focus visible - Accessibility (WCAG 2.2 AA) */
:focus-visible {
	outline: 3px solid var(--color-primary);
	outline-offset: 2px;
}

/* Skip link */
.skip-link {
	position: absolute;
	top: -100px;
	left: 0;
	background: var(--color-primary);
	color: #fff;
	padding: 12px 20px;
	z-index: 9999;
	border-radius: 0 0 var(--radius-sm) 0;
	transition: top var(--transition-fast);
}

.skip-link:focus {
	top: 0;
}

.screen-reader-text {
	position: absolute;
	width: 1px;
	height: 1px;
	overflow: hidden;
	clip: rect(1px, 1px, 1px, 1px);
	white-space: nowrap;
}

/* =========================================================
   LAYOUT
   ========================================================= */
.container {
	width: 100%;
	max-width: var(--container-width);
	margin-inline: auto;
	padding-inline: 24px;
}

.container--alt {
	background-color: var(--color-bg-alt);
}

.section {
	padding-block: var(--section-spacing);
}

.section-title {
	margin-bottom: 32px;
}

.card-grid {
	display: grid;
	grid-template-columns: repeat(4, 1fr);
	gap: var(--card-spacing);
}

.card-grid--categories {
	grid-template-columns: repeat(4, 1fr);
}

/* Dùng cho "Tài liệu nổi bật" và carousel theo từng danh mục cấp 1 ở trang
   chủ - kế thừa mặc định 4 cột từ .card-grid, không cần override gì thêm. */
.card-grid--featured {
	grid-template-columns: repeat(4, 1fr);
}

/* Tablet - 8 columns concept mapped to 2-col cards */
@media (max-width: 1024px) {
	.card-grid,
	.card-grid--categories,
	.card-grid--featured {
		grid-template-columns: repeat(2, 1fr);
	}
}

/* Mobile - 4 columns concept mapped to 1-col cards */
@media (max-width: 640px) {
	.card-grid,
	.card-grid--categories,
	.card-grid--featured {
		grid-template-columns: 1fr;
	}

	.section {
		padding-block: 40px;
	}
}

.responsive-img {
	border-radius: var(--radius-base);
}

/* SVG icon noi bo (lượt xem, lượt tải, số trang, tìm kiếm...) - thay the
   emoji Unicode de tranh trinh duyet/WordPress tu goi Twemoji tu s.w.org. */
.icon-svg {
	display: inline-block;
	vertical-align: -2px;
	flex-shrink: 0;
}

/* Click target >= 44px (Mobile Friendly - TECHNICAL_SEO.md) */
button,
.btn,
a.btn {
	min-height: 44px;
	min-width: 44px;
}