/*
  Mầm non miền Bắc — layout & component styles.
  Nhịp editorial: nhiều khoảng thở, cột đọc hẹp, ghi chú bên lề nổi bằng
  float (không cần JS, không cần subgrid). Phân cấp bằng size/weight/spacing,
  không bằng khung/màu nền.
*/

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

html {
	-webkit-text-size-adjust: 100%;
	color-scheme: light;
}

:target,
[id] {
	scroll-margin-top: 2rem;
}

body {
	margin: 0;
	background: var(--suong);
	color: var(--muc);
	font-family: var(--font-body);
	font-size: var(--text-body);
	line-height: 1.7;
	overflow-wrap: break-word;
}

.sr-only {
	position: absolute;
	width: 1px;
	height: 1px;
	padding: 0;
	margin: -1px;
	overflow: hidden;
	clip: rect(0, 0, 0, 0);
	white-space: nowrap;
	border: 0;
}

.skip-link {
	position: absolute;
	left: 0.5rem;
	top: -4rem;
	z-index: 10;
	padding: 0.7rem 1rem;
	background: var(--cham);
	color: var(--suong);
	font-weight: 600;
	text-decoration: none;
	border-radius: 0.25rem;
	transition: top 0.15s ease;
}
.skip-link:focus {
	top: 0.5rem;
}

.shell {
	width: 100%;
	max-width: var(--shell);
	margin-inline: auto;
	padding-inline: var(--gutter);
}

.measure {
	max-width: var(--measure);
}

.label {
	display: inline-block;
	margin: 0 0 var(--space-s);
	font-size: 0.72rem;
	font-weight: 600;
	letter-spacing: 0.14em;
	text-transform: uppercase;
	color: var(--muc-nhat);
}

h1, h2, h3 {
	font-family: var(--font-display);
	color: var(--cham);
	line-height: 1.15;
	letter-spacing: -0.01em;
	text-wrap: balance;
	margin: 0 0 0.55em;
}
h1 { font-size: var(--text-h1); font-weight: 900; }
h2 { font-size: var(--text-h2); font-weight: 900; }
h3 { font-size: var(--text-h3); font-weight: 600; }

p { margin: 0 0 1.15em; }
strong { font-weight: 600; color: var(--cham); }

a {
	color: var(--dong-muc);
	text-decoration-thickness: 1px;
	text-underline-offset: 0.2em;
}
a:hover { text-decoration-thickness: 2px; }

:focus-visible {
	outline: 3px solid var(--cham);
	outline-offset: 3px;
	border-radius: 2px;
}
.masthead :focus-visible,
.site-footer :focus-visible,
.skip-link:focus-visible {
	outline-color: var(--dong-nhat);
}

/* ---------- Masthead ---------- */

.masthead {
	background: var(--cham);
	color: var(--suong);
}
.masthead__wrap {
	display: flex;
	flex-wrap: wrap;
	align-items: center;
	justify-content: space-between;
	gap: var(--space-s);
	padding-block: var(--space-s);
}
.masthead__title {
	font-family: var(--font-display);
	font-weight: 900;
	font-size: 1.15rem;
	color: var(--suong);
	text-decoration: none;
	letter-spacing: -0.01em;
}
.masthead__nav {
	display: flex;
	flex-wrap: wrap;
	gap: var(--space-m);
	font-size: 0.92rem;
}
.masthead__nav a {
	color: var(--cham-nhat);
	text-decoration: none;
}
.masthead__nav a:hover { color: var(--suong); text-decoration: underline; }

/* ---------- Hero ---------- */

.hero {
	padding-block: var(--space-2xl) var(--space-xl);
}
.hero__title {
	max-width: 20ch;
}
.hero__lead {
	font-size: var(--text-lead);
	color: var(--muc);
	margin-top: var(--space-m);
}

/* ---------- Dải phổ (yếu tố ký tự) ---------- */

.spectrum {
	display: flex;
	align-items: center;
	gap: var(--space-s);
	margin-top: var(--space-l);
}
.spectrum__track {
	flex: 1;
	height: 0.6rem;
	border-radius: 999px;
	background: var(--cham-nhat);
	overflow: hidden;
}
.spectrum__fill {
	display: block;
	height: 100%;
	width: 100%;
	background: linear-gradient(90deg, var(--cham) 0%, var(--cham) 45%, var(--dong) 100%);
}
.spectrum__end {
	font-size: 0.8rem;
	font-weight: 600;
	color: var(--muc-nhat);
	white-space: nowrap;
}
.spectrum--mini .spectrum__end--start { color: var(--cham); }
.spectrum--mini .spectrum__end--stop { color: var(--dong-muc); }

.divider {
	height: 4px;
	background: linear-gradient(90deg, var(--cham) 0%, var(--dong) 100%);
	opacity: 0.55;
}

/* ---------- Intro + margin notes ---------- */

.intro {
	padding-block: var(--space-xl);
}
.layout__content { margin-inline: auto; }

.note {
	margin: 0 0 1.25em;
	padding: var(--space-xs) var(--space-s);
	background: var(--suong-sam);
	border-left: 3px solid var(--dong);
	font-size: var(--text-s);
	color: var(--muc-nhat);
	line-height: 1.55;
	border-radius: 0 0.35rem 0.35rem 0;
}

@media (min-width: 68.75rem) {
	.layout {
		display: block;
	}
	.layout__content {
		margin-inline: 0;
	}
	.note {
		float: right;
		clear: right;
		width: var(--note-w);
		margin-right: calc(-1 * (var(--note-w) + var(--space-l)));
		margin-top: 0.3em;
	}
}

/* ---------- Phần dữ liệu ---------- */

.data-section {
	padding-block: var(--space-xl);
	background: var(--suong-sam);
}
.data-section__note {
	color: var(--muc-nhat);
	font-size: var(--text-s);
	margin-bottom: var(--space-l);
}

.data-scale {
	display: none;
}
@media (min-width: 40rem) {
	.data-scale {
		display: flex;
		gap: var(--space-2xs);
		padding-left: min(34%, 16rem);
		margin-bottom: var(--space-s);
		font-size: 0.72rem;
		font-weight: 600;
		letter-spacing: 0.04em;
		color: var(--muc-nhat);
		text-transform: uppercase;
	}
	.data-scale span {
		flex: 1;
		text-align: center;
	}
}

.data-list {
	list-style: none;
	margin: 0;
	padding: 0;
	display: flex;
	flex-direction: column;
	gap: var(--space-m);
}

.data-row {
	display: flex;
	flex-direction: column;
	gap: var(--space-xs);
}
@media (min-width: 40rem) {
	.data-row {
		flex-direction: row;
		align-items: center;
		gap: var(--space-m);
	}
	.data-row__label {
		flex: 0 0 min(34%, 16rem);
	}
	.data-row__bar {
		flex: 1;
	}
}

.data-row__label {
	font-weight: 600;
	color: var(--cham);
	font-size: 0.95rem;
}
.data-row__sub {
	display: block;
	font-weight: 400;
	color: var(--muc-nhat);
	font-size: 0.82rem;
	margin-top: 0.2em;
}

.data-row__bar {
	display: flex;
	gap: 3px;
	height: 1.75rem;
}
.seg {
	flex: 1;
	background: var(--vien);
	border-radius: 3px;
}
.seg--on {
	background: var(--cham);
}
.data-row:nth-child(1) .seg--on { background: var(--cham); }
.data-row:nth-child(2) .seg--on { background: #3c4a72; }
.data-row:nth-child(3) .seg--on { background: #56628a; }
.data-row:nth-child(4) .seg--on { background: var(--dong); }

.data-table-toggle {
	margin-top: var(--space-l);
	font-size: 0.9rem;
}
.data-table-toggle summary {
	cursor: pointer;
	font-weight: 600;
	color: var(--dong-muc);
}
.table-scroll {
	overflow-x: auto;
	margin-top: var(--space-s);
	border: 1px solid var(--vien);
	border-radius: 0.35rem;
}
table {
	width: 100%;
	min-width: 34rem;
	border-collapse: collapse;
	font-size: 0.92rem;
}
th, td {
	padding: 0.65rem 0.85rem;
	text-align: left;
	vertical-align: top;
	border-bottom: 1px solid var(--vien);
}
thead th {
	background: var(--suong);
	color: var(--cham);
	font-size: 0.75rem;
	letter-spacing: 0.06em;
	text-transform: uppercase;
}
tbody tr:last-child td { border-bottom: 0; }

/* ---------- Hai bài toán ---------- */

.problems {
	padding-block: var(--space-xl);
}
.problems h2 {
	max-width: 28ch;
}
.problems__grid {
	display: grid;
	gap: var(--space-m);
	margin-top: var(--space-l);
}
@media (min-width: 44rem) {
	.problems__grid {
		grid-template-columns: 1fr 1fr;
	}
}
.problem-card {
	padding: var(--space-m);
	background: var(--suong-sam);
	border-radius: 0.5rem;
}
.problem-card__stat {
	font-family: var(--font-display);
	font-weight: 900;
	font-size: 1.3rem;
	color: var(--dong-muc);
	margin-bottom: 0.5em;
}

/* ---------- Cách đọc phổ này ---------- */

.framework {
	padding-block: var(--space-xl);
}
.framework__list {
	padding-left: 1.25em;
	display: flex;
	flex-direction: column;
	gap: 1em;
}
.framework__list li { padding-left: 0.25em; }

/* ---------- FAQ ---------- */

.faq {
	padding-block: var(--space-xl);
}
.faq__list {
	max-width: var(--measure);
	display: flex;
	flex-direction: column;
	gap: var(--space-xs);
	margin-top: var(--space-l);
}
.faq__item {
	border-bottom: 1px solid var(--vien);
	padding-block: var(--space-s);
}
.faq__item summary {
	cursor: pointer;
	font-weight: 600;
	color: var(--cham);
	font-size: 1.02rem;
}
.faq__item p {
	margin-top: var(--space-s);
	margin-bottom: 0;
	color: var(--muc);
}

/* ---------- Footer ---------- */

.site-footer {
	background: var(--cham);
	color: var(--cham-nhat);
	padding-block: var(--space-l);
	margin-top: var(--space-xl);
}
.site-footer__links {
	display: flex;
	flex-wrap: wrap;
	gap: var(--space-m);
	margin-bottom: var(--space-s);
}
.site-footer__links a {
	color: var(--suong);
	text-decoration: none;
	font-size: 0.92rem;
}
.site-footer__links a:hover { text-decoration: underline; }
.site-footer__meta {
	margin: 0;
	font-size: 0.8rem;
	color: var(--cham-nhat);
}

/* ---------- Bài viết (mini-SSG output) ---------- */

.article {
	padding-block: var(--space-2xl) var(--space-l);
}
.article__title {
	max-width: 26ch;
}
.article-body {
	padding-block: var(--space-l) var(--space-xl);
}

.hero--compact {
	padding-block: var(--space-xl) var(--space-l);
}

.article-list {
	padding-block: var(--space-l) var(--space-xl);
}
.article-list__items {
	list-style: none;
	margin: 0;
	padding: 0;
	max-width: var(--measure);
	display: flex;
	flex-direction: column;
	gap: var(--space-m);
}
.article-list__item a {
	display: block;
	padding: var(--space-m);
	background: var(--suong-sam);
	border-radius: 0.5rem;
	text-decoration: none;
	color: inherit;
}
.article-list__title {
	display: block;
	font-family: var(--font-display);
	font-weight: 900;
	font-size: 1.15rem;
	color: var(--cham);
	margin-bottom: 0.3em;
}
.article-list__item a:hover .article-list__title {
	text-decoration: underline;
}
.article-list__desc {
	display: block;
	color: var(--muc);
	font-size: 0.95rem;
	margin-bottom: 0.5em;
}
.article-list__date {
	display: block;
	font-size: 0.8rem;
	color: var(--muc-nhat);
}
.article-list__empty {
	color: var(--muc-nhat);
}

@media (prefers-reduced-motion: reduce) {
	*, *::before, *::after {
		animation-duration: 0.01ms !important;
		animation-iteration-count: 1 !important;
		transition-duration: 0.01ms !important;
		scroll-behavior: auto !important;
	}
}