/* Landing: trang là tấm phiếu "Bài học" của series, giấy dó trên nền gỗ (taste-skill: page-is-the-object, seed 610579854).
   Phông Baloo 2 lấy từ phong cách series (01-ke-tu-tao-van-menh-2d/phong-cach/proj/public/fonts, SIL OFL). */
@font-face { font-family: "Baloo 2"; font-weight: 800; font-display: swap; src: url(/phong/baloo-2-vietnamese-800-normal.woff2) format("woff2"); unicode-range: U+0102-0103, U+0110-0111, U+0128-0129, U+0168-0169, U+01A0-01A1, U+01AF-01B0, U+0300-0301, U+0303-0304, U+0308-0309, U+0323, U+0329, U+1EA0-1EF9, U+20AB; }
@font-face { font-family: "Baloo 2"; font-weight: 800; font-display: swap; src: url(/phong/baloo-2-latin-800-normal.woff2) format("woff2"); unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD; }

@font-face { font-family: "Patrick Hand"; font-weight: 400; font-display: swap; src: url(/phong/patrick-hand-vietnamese-400-normal.woff2) format("woff2"); unicode-range: U+0102-0103, U+0110-0111, U+0128-0129, U+0168-0169, U+01A0-01A1, U+01AF-01B0, U+0300-0301, U+0303-0304, U+0308-0309, U+0323, U+0329, U+1EA0-1EF9, U+20AB; }
@font-face { font-family: "Patrick Hand"; font-weight: 400; font-display: swap; src: url(/phong/patrick-hand-latin-400-normal.woff2) format("woff2"); unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD; }

:root {
  --nen: #3b2414;        /* gỗ thuốc lá */
  --nen-2: #4a2e19;
  --giay: #e6e1cf;       /* giấy dó */
  --giay-2: #d9d2ba;
  --muc: #2b1a0e;        /* mực trên giấy */
  --muc-phu: #5e4a36;
  --sang: #e3e0d6;       /* chữ trên nền gỗ */
  --sang-phu: #c4b69c;
  --do: #c8363a;         /* đỏ son con dấu "Bài học" */
  --la: #4f6b2a;         /* xanh lá Mầm — nút */
  --la-chu: #e3e0d6;
  --le: clamp(16px, 3vw, 40px);
  --rong: 1240px;
  --chu-nho: 0.9375rem;
  --chu: clamp(1.125rem, 1.07rem + 0.25vw, 1.3125rem);
  --chu-lon: clamp(1.25rem, 1.1rem + 0.7vw, 1.625rem);
  --tieu-de: clamp(2rem, 1.2rem + 3.4vw, 4rem);
  --tieu-de-lon: clamp(2.5rem, 1.2rem + 5vw, 5.5rem);
  --hien: cubic-bezier(.2, .7, .2, 1);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--nen); color: var(--sang); font: 400 var(--chu)/1.6 "Patrick Hand", "Baloo 2", system-ui, sans-serif; overflow-x: hidden; }
h1, h2, h3 { font-family: "Baloo 2", system-ui, sans-serif; font-weight: 800; letter-spacing: -0.02em; line-height: 1.02; margin: 0; text-wrap: balance; }
p { margin: 0; }
img, video { display: block; max-width: 100%; height: auto; }
a { color: inherit; }
:focus-visible { outline: 3px solid var(--do); outline-offset: 3px; }
::selection { background: var(--do); color: var(--giay); }

.bo-qua { position: absolute; left: -9999px; }
.bo-qua:focus { left: var(--le); top: 8px; z-index: 20; background: var(--giay); color: var(--muc); padding: 8px 12px; }

/* Thanh trên: chữ, vài link, đổi ngôn ngữ. */
.thanh { position: relative; z-index: 5; display: flex; align-items: center; gap: 24px; max-width: var(--rong); margin: 0 auto; padding: 20px var(--le); }
.ten-trang { font-family: "Baloo 2", system-ui, sans-serif; font-weight: 800; font-size: var(--chu); text-decoration: none; margin-right: auto; }
.dieu-huong { display: flex; gap: 24px; }
.dieu-huong a { text-decoration: none; color: var(--sang-phu); transition: color .2s; }
.dieu-huong a:hover { color: var(--sang); }

/* Tấm phiếu giấy dó: mép dưới răng cưa như tem/phiếu xé. */
.phieu { background: var(--giay) url(/hinh/giay.webp) center / cover; color: var(--muc); }
.rang-cua { --r: 10px; mask: radial-gradient(circle var(--r) at 50% 100%, #0000 98%, #000) 50% 0 / calc(2 * var(--r) + 6px) 100% repeat-x; /* taste-skill-ignore: mặt nạ cắt mép răng cưa, không phải màu */ }

/* ---------- Màn đầu ---------- */
.mo-dau { max-width: var(--rong); margin: 0 auto; padding: 24px var(--le) 0; }
.phieu-lon { display: grid; grid-template-columns: minmax(0, 6fr) minmax(0, 6fr); grid-template-areas: "dau hinh" "dan hinh" "chan hinh"; gap: 24px 48px; align-content: start; padding: clamp(24px, 4vw, 56px); --r: 12px; mask: radial-gradient(circle var(--r) at 50% 100%, #0000 98%, #000) 50% 0 / 30px 100% repeat-x; /* taste-skill-ignore: mặt nạ cắt mép răng cưa, không phải màu */ padding-bottom: calc(clamp(24px, 4vw, 56px) + 12px); }
.phieu-dau { grid-area: dau; display: flex; flex-direction: column; gap: 20px; align-items: flex-start; }
.phieu-lon h1 { font-size: var(--tieu-de-lon); line-height: .95; }
.dau-do { display: inline-grid; place-items: center; transform: rotate(-6deg); background: var(--do); color: var(--giay); font-family: "Baloo 2", system-ui, sans-serif; font-weight: 800; line-height: 1; padding: 10px 16px 8px; border-radius: 10px; font-size: var(--chu-nho); }
.dau-do b { font-size: var(--chu-lon); }
.phieu-lon .dan { grid-area: dan; font-size: var(--chu-lon); line-height: 1.45; max-width: 30ch; color: var(--muc); }
.phieu-hinh { grid-area: hinh; margin: 0; align-self: center; }
.phieu-hinh video { width: 100%; aspect-ratio: 16 / 9; object-fit: cover; background: var(--giay-2); }
.phieu-hinh figcaption { margin-top: 10px; font-size: var(--chu-nho); color: var(--muc-phu); }
.phieu-chan { grid-area: chan; display: flex; flex-wrap: wrap; align-items: center; gap: 16px 28px; align-self: end; }
.nut { display: inline-flex; align-items: center; justify-content: center; min-height: 48px; padding: 0 24px; border-radius: 999px; background: var(--la); color: var(--la-chu); font-weight: 600; text-decoration: none; transition: transform .15s var(--hien), background .2s; }
.nut:hover { background: #5d7d32; transform: translateY(-2px); }
.nut:active { transform: translateY(0) scale(.98); }
.lien-ket { font-weight: 600; color: var(--muc); text-underline-offset: 4px; }
.lien-ket:hover { color: var(--do); }
.slogan { font-family: "Baloo 2", system-ui, sans-serif; font-weight: 800; font-size: var(--chu-lon); color: var(--sang); margin: 40px 0 0; max-width: 40ch; }

/* ---------- Ba con số thật dưới tấm phiếu đầu ---------- */
.so-that { list-style: none; margin: clamp(48px, 6vw, 88px) 0 0; padding: 0; display: flex; justify-content: space-between; gap: 24px 32px; flex-wrap: wrap; }
.so-that li { display: grid; gap: 4px; }
.so-that b { font-family: "Baloo 2", system-ui, sans-serif; font-weight: 800; font-size: var(--tieu-de); line-height: 1; letter-spacing: -0.02em; }
.so-that span { color: var(--sang-phu); font-size: var(--chu-nho); }
.nut-nho { min-height: 44px; padding: 0 20px; }
button.nut { border: 0; font: inherit; font-weight: 600; cursor: pointer; }

/* ---------- Chọn vấn đề của bạn ---------- */
.van-de { max-width: var(--rong); margin: 0 auto; padding: clamp(120px, 14vw, 220px) var(--le) 0; display: grid; grid-template-columns: minmax(0, 5fr) minmax(0, 7fr); gap: 48px; align-items: start; }
.van-de h2 { font-size: var(--tieu-de); }
.van-de-chu { display: grid; gap: 24px; align-content: start; }
.van-de-chu > p { color: var(--sang); max-width: 40ch; }
.ds-van-de { list-style: none; margin: 0; padding: 0; display: grid; gap: 8px; }
.van-de-nut { width: 100%; text-align: left; font: inherit; font-size: var(--chu); color: var(--sang); background: var(--nen-2); border: 0; border-radius: 6px; min-height: 52px; padding: 10px 18px; cursor: pointer; transition: background .2s, color .2s, transform .15s var(--hien); }
.van-de-nut:hover { background: #5a3a22; transform: translateX(4px); }
.van-de-nut[aria-pressed="true"] { background: var(--giay); color: var(--muc); font-weight: 600; }
.phieu-bai { display: grid; gap: 16px; padding: clamp(24px, 3vw, 40px); padding-bottom: calc(clamp(24px, 3vw, 40px) + 10px); --r: 10px; mask: radial-gradient(circle var(--r) at 50% 100%, #0000 98%, #000) 50% 0 / 26px 100% repeat-x; /* taste-skill-ignore: mặt nạ cắt mép răng cưa, không phải màu */ }
.mam { width: 110px; justify-self: start; }
.phieu-bai h3 { font-size: var(--chu-lon); line-height: 1.1; }
.buoc-nho { display: grid; gap: 4px; max-width: 54ch; }
.buoc-nho b { color: var(--do); }
.khung-the { position: relative; aspect-ratio: 16 / 9; background: var(--giay-2); }
.khung-the .anh-bai, .khung-the iframe { position: absolute; inset: 0; width: 100%; height: 100%; border: 0; object-fit: cover; display: block; }
.nut-phat { position: absolute; right: 14px; bottom: 14px; display: inline-flex; align-items: center; justify-content: center; min-height: 48px; padding: 0 22px; border: 0; border-radius: 999px; background: var(--la); color: var(--la-chu); font: inherit; font-weight: 700; cursor: pointer; transition: transform .15s var(--hien), background .2s; }
.nut-phat:hover { background: #5d7d32; transform: translateY(-2px); }
.nut-phat:active { transform: scale(.97); }
.anh-bai.doi { animation: doi-anh .4s var(--hien); }

/* ---------- Tất cả bài ---------- */
.tat-ca { max-width: var(--rong); margin: 0 auto; padding: clamp(120px, 14vw, 220px) var(--le) 0; }
.tat-ca-dau { display: grid; grid-template-columns: minmax(0, 6fr) minmax(0, 5fr); gap: 16px 48px; align-items: end; }
.tat-ca h2 { font-size: var(--tieu-de); }
.tien-do { display: grid; gap: 12px; }
.tien-do b { font-family: "Baloo 2", system-ui, sans-serif; font-weight: 800; color: var(--giay); }
.thanh-tien-do { height: 14px; border-radius: 999px; background: var(--nen-2); overflow: hidden; }
.thanh-tien-do span { display: block; height: 100%; width: 0; background: var(--la); border-radius: 999px; transition: width .9s var(--hien); }
.luoi-bai { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 40px 24px; margin-top: 56px; }
.the-bai { display: grid; gap: 8px; text-align: left; font: inherit; color: var(--sang); background: none; border: 0; padding: 0; cursor: pointer; align-content: start; }
.the-bai img { width: 100%; aspect-ratio: 16 / 9; object-fit: cover; background: var(--giay-2); transition: transform .3s var(--hien); }
.the-bai:hover img { transform: scale(1.03); }
.the-bai small { color: var(--sang-phu); font-size: var(--chu-nho); }
.the-bai .ten { font-weight: 600; line-height: 1.3; }
.the-bai:focus-visible img { outline: 3px solid var(--do); outline-offset: 3px; }

/* ---------- Mầm và Đông Hồ ---------- */
.mam-phan { max-width: var(--rong); margin: 0 auto; padding: clamp(120px, 14vw, 220px) var(--le) 0; display: grid; grid-template-columns: minmax(0, 5fr) minmax(0, 7fr); gap: 48px; align-items: center; }
.mam-chu { display: grid; gap: 20px; align-content: start; }
.mam-chu h2 { font-size: var(--tieu-de); }
.mam-chu p { max-width: 46ch; }
.chibi { width: 100%; height: auto; background: var(--giay); }
.mam-giai-doan { grid-column: 1 / -1; list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 16px; align-items: end; }
.mam-giai-doan li { display: grid; gap: 8px; justify-items: center; background: var(--giay); color: var(--muc); padding: 16px 8px 12px; }
.mam-giai-doan img { height: clamp(72px, 9vw, 128px); width: auto; }
.mam-giai-doan span { font-weight: 600; }
.mam-giai-doan li:nth-child(2) { padding-top: 8px; }
.mam-giai-doan li:nth-child(3) { padding-top: 0; }

/* ---------- Chân trang: mặt sau tấm phiếu, mép trên răng cưa ---------- */
.chan { max-width: var(--rong); margin: 0 auto; padding: clamp(120px, 14vw, 220px) var(--le) var(--le); }
.phieu-sau { display: grid; grid-template-columns: minmax(0, 7fr) minmax(0, 4fr); gap: 32px 48px; padding: calc(clamp(28px, 4vw, 56px) + 12px) clamp(24px, 4vw, 56px) clamp(24px, 3vw, 40px); --r: 12px; mask: radial-gradient(circle var(--r) at 50% 0, #0000 98%, #000) 50% 0 / 30px 100% repeat-x; /* taste-skill-ignore: mặt nạ cắt mép răng cưa, không phải màu */ }
.chan-loi { font-family: "Baloo 2", system-ui, sans-serif; font-weight: 800; font-size: var(--tieu-de); line-height: 1; margin-bottom: 16px; }
.phieu-sau > div { display: grid; gap: 16px; align-content: start; justify-items: start; }
.chan-link { list-style: none; margin: 0; padding: 0; display: grid; gap: 12px; align-content: start; }
.chan-link a { font-weight: 600; text-underline-offset: 4px; }
.chan-link a:hover { color: var(--do); }
.chan-in { grid-column: 1 / -1; font-size: var(--chu-nho); color: var(--muc-phu); }

/* ---------- Hộp phát ---------- */
dialog { width: min(960px, calc(100vw - 32px)); max-height: calc(100dvh - 32px); padding: 16px; background: var(--giay); color: var(--muc); border: 0; border-radius: 4px; box-shadow: 0 24px 80px #0009; } /* taste-skill-ignore: hộp phát nổi trên trang */
dialog::backdrop { background: #1a0e06cc; }
.dau-hop { display: flex; justify-content: space-between; gap: 12px; align-items: start; margin-bottom: 12px; }
.dau-hop h2 { font-size: var(--chu-lon); }
.nut-dong { min-width: 44px; min-height: 44px; border: 0; border-radius: 999px; background: var(--giay-2); color: var(--muc); font-size: var(--chu-lon); cursor: pointer; }
.khung-video { aspect-ratio: 16 / 9; background: #000; }
.khung-video iframe { width: 100%; height: 100%; border: 0; display: block; }
dialog > .nut { margin-top: 12px; }

/* ---------- Chuyển động: hiện dần từng phần khi cuộn tới (chỉ khi có JS) ---------- */
.co-js .hien-dan > *, .co-js .vao > * { opacity: 0; transform: translateY(24px); transition: opacity .6s var(--hien), transform .6s var(--hien); }
.co-js .hien-dan.da-hien > *, .co-js .vao.da-hien > * { opacity: 1; transform: none; }
.co-js .da-hien > :nth-child(2) { transition-delay: 80ms; }
.co-js .da-hien > :nth-child(3) { transition-delay: 160ms; }
.co-js .da-hien > :nth-child(4) { transition-delay: 240ms; }
.co-js .da-hien > :nth-child(n+5) { transition-delay: 300ms; }
@keyframes doi-anh { from { opacity: .3; transform: translateY(8px); } to { opacity: 1; transform: none; } }

/* ---------- Máy tính bảng / điện thoại ---------- */
@media (max-width: 900px) {
  .ds-van-de { display: flex; flex-wrap: wrap; gap: 8px; }
  .ds-van-de li { flex: 0 1 auto; }
  .van-de-nut { width: auto; min-height: 44px; padding: 8px 16px; border-radius: 999px; }
  .van-de-nut:hover { transform: none; }
  .phieu-lon { grid-template-columns: minmax(0, 1fr); grid-template-areas: "dau" "dan" "hinh" "chan"; }
  .van-de, .mam-phan, .tat-ca-dau { grid-template-columns: minmax(0, 1fr); }
  .luoi-bai { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .so-that { justify-content: flex-start; }
}
@media (max-width: 640px) {
  .dieu-huong { display: none; }
  .thanh { padding-block: 14px; }
  .phieu-sau { grid-template-columns: minmax(0, 1fr); }
  .phieu-lon { padding-top: 40px; }
  .luoi-bai { grid-template-columns: minmax(0, 1fr); gap: 32px; }
  .so-that { display: grid; grid-template-columns: minmax(0, 1fr); gap: 24px; }
  .so-that b { font-size: clamp(1.75rem, 8vw, 2.5rem); }
  .mam-giai-doan { grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 8px; }
  .mam-giai-doan li { padding: 10px 4px 8px; }
  .mam-giai-doan span { font-size: var(--chu-nho); }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .co-js .hien-dan > *, .co-js .vao > * { opacity: 1; transform: none; transition: none; }
  .anh-bai.doi { animation: none; }
}