/* Cú Pi Math — trang công khai cupimath.com
   Hướng thiết kế: tạp chí sáng trên nền "giấy kẻ ô" của vở toán; mực navy (mắt Cú Pi), teal thương hiệu, cam hành động. */

/* ---------- Font (tự host, Be Vietnam Pro — OFL, xem fonts/OFL.txt) ---------- */
@font-face { font-family: 'Be Vietnam Pro'; font-style: normal; font-weight: 400; font-display: swap;
  src: url(fonts/be-vietnam-pro-400-vietnamese.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: 'Be Vietnam Pro'; font-style: normal; font-weight: 400; font-display: swap;
  src: url(fonts/be-vietnam-pro-400-latin.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: 'Be Vietnam Pro'; font-style: normal; font-weight: 700; font-display: swap;
  src: url(fonts/be-vietnam-pro-700-vietnamese.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: 'Be Vietnam Pro'; font-style: normal; font-weight: 700; font-display: swap;
  src: url(fonts/be-vietnam-pro-700-latin.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: 'Be Vietnam Pro'; font-style: normal; font-weight: 800; font-display: swap;
  src: url(fonts/be-vietnam-pro-800-vietnamese.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: 'Be Vietnam Pro'; font-style: normal; font-weight: 800; font-display: swap;
  src: url(fonts/be-vietnam-pro-800-latin.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; }

/* ---------- Token ---------- */
:root {
  --paper: #fbf8f1;
  --paper-2: #f3eee2;
  --surface: #ffffff;
  --ink: #1b1f3b;
  --ink-2: #4a4f6e;
  --ink-3: #6b7090;
  --line: #e4ddcc;
  --grid: rgb(27 31 59 / 0.055);
  --teal: #0e7c70;
  --teal-bright: #26b8a4;
  --teal-soft: #d9f3ee;
  --orange: #f47c00;
  --orange-ink: #2a1600;
  --orange-soft: #ffe9d1;
  --blue-soft: #e2ecff;
  --blue: #3355d1;
  --gold: #b27800;
  --phone: #14172c;
  --shadow-lg: 0 30px 60px -20px rgb(27 31 59 / 0.35), 0 12px 24px -12px rgb(27 31 59 / 0.2);
  --shadow-sm: 0 1px 0 rgb(27 31 59 / 0.06), 0 6px 18px -8px rgb(27 31 59 / 0.18);

  --font: 'Be Vietnam Pro', system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --text-sm: 0.875rem;
  --text-base: clamp(1rem, 0.96rem + 0.2vw, 1.0625rem);
  --text-lead: clamp(1.0625rem, 1rem + 0.4vw, 1.25rem);
  --text-h3: clamp(1.25rem, 1.1rem + 0.6vw, 1.5rem);
  --text-h2: clamp(1.75rem, 1.3rem + 2vw, 2.75rem);
  --text-hero: clamp(2.35rem, 1.4rem + 4.4vw, 4.5rem);

  --gutter: 16px;
  --wrap: 1180px;
  --space-section: clamp(4rem, 3rem + 5vw, 8rem);
  --radius-sm: 10px;
  --radius: 18px;
  --radius-lg: 28px;

  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --duration-fast: 150ms;
  --duration: 600ms;
  color-scheme: light;
}
@media (min-width: 720px) { :root { --gutter: 32px; } }

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #10132a; --paper-2: #161a36; --surface: #1b2041;
    --ink: #eef0fa; --ink-2: #bcc1dc; --ink-3: #9398b8;
    --line: #2b3158; --grid: rgb(238 240 250 / 0.045);
    --teal: #4fd8c4; --teal-bright: #4fd8c4; --teal-soft: #173a3f;
    --orange: #ff9a2e; --orange-ink: #2a1600; --orange-soft: #3a2a18;
    --blue-soft: #1e2a57; --blue: #9db2ff; --gold: #ffc44d; --phone: #05060f;
    --shadow-lg: 0 30px 60px -20px rgb(0 0 0 / 0.6), 0 12px 24px -12px rgb(0 0 0 / 0.5);
    --shadow-sm: 0 1px 0 rgb(0 0 0 / 0.3), 0 6px 18px -8px rgb(0 0 0 / 0.5);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --paper: #10132a; --paper-2: #161a36; --surface: #1b2041;
  --ink: #eef0fa; --ink-2: #bcc1dc; --ink-3: #9398b8;
  --line: #2b3158; --grid: rgb(238 240 250 / 0.045);
  --teal: #4fd8c4; --teal-bright: #4fd8c4; --teal-soft: #173a3f;
  --orange: #ff9a2e; --orange-ink: #2a1600; --orange-soft: #3a2a18;
  --blue-soft: #1e2a57; --blue: #9db2ff; --gold: #ffc44d; --phone: #05060f;
  color-scheme: dark;
}

/* ---------- Nền tảng ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; scroll-padding-top: 88px; }
body {
  margin: 0; background: var(--paper); color: var(--ink);
  font: 400 var(--text-base)/1.65 var(--font);
  -webkit-font-smoothing: antialiased; text-rendering: optimizeLegibility;
  overflow-x: hidden;
}
img { max-width: 100%; height: auto; display: block; }
a { color: var(--teal); text-underline-offset: 3px; text-decoration-thickness: 1.5px; }
a:hover { text-decoration-thickness: 2.5px; }
:focus-visible { outline: 3px solid var(--orange); outline-offset: 3px; border-radius: 6px; }
h1, h2, h3 { line-height: 1.12; letter-spacing: -0.02em; margin: 0; font-weight: 800; text-wrap: balance; }
p { margin: 0 0 1em; text-wrap: pretty; }
.wrap { width: 100%; max-width: var(--wrap); margin: 0 auto; padding: 0 var(--gutter); }
.skip { position: absolute; left: -999px; top: 8px; background: var(--ink); color: var(--paper); padding: 8px 14px; border-radius: 8px; z-index: 100; }
.skip:focus { left: 8px; }
.visually-hidden { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

/* giấy kẻ ô */
.grid-paper {
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 28px 28px;
  background-position: -1px -1px;
}

/* ---------- Header ---------- */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--paper) 86%, transparent);
  backdrop-filter: saturate(1.4) blur(12px); -webkit-backdrop-filter: saturate(1.4) blur(12px);
  border-bottom: 1px solid transparent;
  transition: border-color var(--duration-fast);
}
.site-header.is-scrolled { border-bottom-color: var(--line); }
.site-header .wrap { display: flex; align-items: center; gap: 20px; min-height: 68px; }
.brand { display: inline-flex; align-items: center; gap: 10px; color: var(--ink); text-decoration: none; font-weight: 800; font-size: 1.125rem; letter-spacing: -0.01em; }
.brand img { width: 38px; height: 38px; }
.brand span { white-space: nowrap; }
.site-nav { display: flex; gap: 4px; margin-left: auto; }
.site-nav a { color: var(--ink-2); text-decoration: none; font-weight: 500; font-size: 0.95rem; padding: 8px 12px; border-radius: 999px; transition: background var(--duration-fast), color var(--duration-fast); }
.site-nav a:hover { background: var(--paper-2); color: var(--ink); }
.site-nav a[aria-current="page"] { color: var(--ink); background: var(--paper-2); }
.header-cta { flex-shrink: 0; }
@media (max-width: 859px) {
  .site-header .wrap { flex-wrap: wrap; gap: 0 12px; padding-top: 10px; }
  .header-cta { margin-left: auto; }
  .site-nav { order: 3; width: 100%; margin: 4px 0 6px; overflow-x: auto; scrollbar-width: none; mask-image: linear-gradient(90deg, #000 88%, transparent); }
  .site-nav::-webkit-scrollbar { display: none; }
  .site-nav a { white-space: nowrap; padding: 6px 12px; font-size: 0.9rem; }
  html { scroll-padding-top: 120px; }
}

/* ---------- Nút ---------- */
.btn {
  --btn-bg: var(--orange); --btn-fg: var(--orange-ink); --btn-edge: color-mix(in srgb, var(--orange) 70%, #000);
  display: inline-flex; align-items: center; justify-content: center; gap: 10px;
  min-height: 48px; padding: 12px 22px; border-radius: 14px;
  background: var(--btn-bg); color: var(--btn-fg); font: 700 1rem/1.2 var(--font); text-decoration: none;
  box-shadow: 0 4px 0 var(--btn-edge);
  transition: transform var(--duration-fast) var(--ease-out), box-shadow var(--duration-fast) var(--ease-out), filter var(--duration-fast);
}
.btn:hover { filter: brightness(1.05); transform: translateY(-1px); box-shadow: 0 5px 0 var(--btn-edge); text-decoration: none; }
.btn:active { transform: translateY(4px); box-shadow: 0 0 0 var(--btn-edge); }
.btn svg { width: 18px; height: 18px; transition: transform var(--duration-fast) var(--ease-out); }
.btn:hover svg { transform: translateX(3px); }
.btn-sm { min-height: 40px; padding: 8px 16px; font-size: 0.925rem; border-radius: 12px; box-shadow: 0 3px 0 var(--btn-edge); }
.btn-ghost { --btn-bg: var(--surface); --btn-fg: var(--ink); --btn-edge: var(--line); border: 1.5px solid var(--line); }

/* ---------- Hero ---------- */
.hero { position: relative; padding: clamp(2.5rem, 2rem + 4vw, 6rem) 0 clamp(3rem, 2rem + 5vw, 7rem); overflow: hidden; }
.hero::after { /* mờ dần giấy kẻ ô ở mép dưới */
  content: ""; position: absolute; inset: auto 0 0 0; height: 30%; pointer-events: none;
  background: linear-gradient(transparent, var(--paper));
}
.hero .wrap { position: relative; z-index: 1; display: grid; gap: clamp(2.5rem, 2rem + 3vw, 4rem); align-items: center; }
@media (min-width: 960px) { .hero .wrap { grid-template-columns: 1.08fr 0.92fr; } }
.eyebrow {
  display: inline-flex; align-items: center; gap: 8px; margin-bottom: 20px;
  font-size: var(--text-sm); font-weight: 700; letter-spacing: 0.02em; color: var(--teal);
  background: var(--teal-soft); padding: 6px 14px 6px 8px; border-radius: 999px;
}
.eyebrow .dot { width: 18px; height: 18px; border-radius: 50%; background: var(--teal); display: grid; place-items: center; color: var(--paper); font-size: 11px; }
.hero h1 { font-size: var(--text-hero); letter-spacing: -0.035em; line-height: 1.04; }
.hero h1 em { font-style: normal; color: var(--teal); position: relative; white-space: nowrap; }
.hero h1 em::after { /* nét gạch chân kiểu bút dạ */
  content: ""; position: absolute; left: -2%; right: -2%; bottom: 0.02em; height: 0.2em; z-index: -1;
  background: var(--orange-soft); border-radius: 4px; transform: rotate(-1deg);
}
.hero .lead { font-size: var(--text-lead); color: var(--ink-2); max-width: 36em; margin: 24px 0 32px; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 14px; align-items: center; }
.hero-note { margin-top: 18px; font-size: var(--text-sm); color: var(--ink-3); display: flex; gap: 8px 18px; flex-wrap: wrap; }
.hero-note span { display: inline-flex; align-items: center; gap: 6px; }
.hero-note svg { width: 16px; height: 16px; color: var(--teal); flex-shrink: 0; }

/* bộ đôi điện thoại */
.hero-visual { position: relative; width: 100%; max-width: 520px; margin: 0 auto; aspect-ratio: 10 / 13; display: grid; place-items: center; }
.hero-visual .phone { position: absolute; width: min(58%, 290px); }
.hero-visual .phone-back { transform: translate(-34%, -2%) rotate(-7deg); z-index: 1; }
.hero-visual .phone-front { transform: translate(30%, 6%) rotate(5deg); z-index: 2; }
.chip-float {
  position: absolute; z-index: 3; display: flex; align-items: center; gap: 10px;
  background: var(--surface); color: var(--ink); border: 1px solid var(--line); border-radius: 16px;
  padding: 10px 14px; box-shadow: var(--shadow-sm); font-size: var(--text-sm); line-height: 1.3;
}
.chip-float b { display: block; font-size: 0.95rem; }
.chip-float small { color: var(--ink-3); font-size: 0.8rem; }
.chip-float .ico { width: 34px; height: 34px; border-radius: 10px; display: grid; place-items: center; flex-shrink: 0; font-weight: 800; }
.chip-award { top: 8%; right: 0; }
.chip-award .ico { background: var(--orange-soft); color: var(--gold); }
.chip-gloss { bottom: 10%; left: 0; }
.chip-gloss .ico { background: var(--blue-soft); color: var(--blue); font-size: 0.75rem; }
@media (max-width: 520px) { .chip-float { padding: 8px 10px; } .chip-float small { display: none; } .chip-award { top: 2%; } .chip-gloss { bottom: 4%; } }

/* ---------- Khung điện thoại ----------
   Ảnh chụp app không có thanh trạng thái → khung tự vẽ dải trạng thái (giờ, tai thỏ, pin) phía trên,
   nội dung app bắt đầu ngay dưới tai thỏ nên không bị che. Kích thước theo cqw (độ rộng khung). */
.phone { /* cqw chỉ dùng được cho phần tử con → viền, bo góc, bóng đặt trên img */
  container-type: inline-size; position: relative;
}
figure.phone { margin: 0; }
.phone::before { /* tai thỏ */
  content: ""; position: absolute; z-index: 1; top: calc(3cqw + 2.6cqw); left: 50%; transform: translateX(-50%);
  width: 29cqw; height: 8.4cqw; border-radius: 999px; background: var(--phone);
}
.phone::after { /* giờ */
  content: "9:41"; position: absolute; z-index: 1; top: calc(3cqw + 3.6cqw); left: 13cqw;
  font: 700 4.6cqw/1.4 var(--font); color: #111; letter-spacing: -0.01em;
}
.phone img {
  width: 100%; aspect-ratio: 600 / 1299; object-fit: cover; object-position: top;
  padding-top: 13.5cqw; border: 3cqw solid var(--phone); border-radius: 15cqw; box-shadow: var(--shadow-lg);
  /* sóng + pin ở góc phải dải trạng thái */
  background: #fff url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 44 12'%3E%3Cg fill='%23111'%3E%3Crect x='0' y='7' width='3' height='4' rx='1'/%3E%3Crect x='4.5' y='5' width='3' height='6' rx='1'/%3E%3Crect x='9' y='3' width='3' height='8' rx='1'/%3E%3Crect x='13.5' y='1' width='3' height='10' rx='1'/%3E%3Crect x='22' y='1' width='19' height='10' rx='3' fill='none' stroke='%23111' stroke-opacity='.45'/%3E%3Crect x='24' y='3' width='15' height='6' rx='1.6'/%3E%3Crect x='42' y='4' width='1.6' height='4' rx='.8' fill-opacity='.45'/%3E%3C/g%3E%3C/svg%3E") no-repeat right 11cqw top 6.4cqw / 16cqw auto;
}
.phone.is-short img { aspect-ratio: 600 / 800; }
/* màn có lớp phủ tối (hộp chọn cuộc thi): dải trạng thái cũng tối theo */
.phone.is-dimmed img { background-color: #767779; }
.phone.is-dimmed::after { color: #fff; }

/* ---------- Dải số liệu ---------- */
.stats { border-block: 1px solid var(--line); background: var(--surface); }
.stats ul { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(2, 1fr); }
@media (min-width: 760px) { .stats ul { grid-template-columns: repeat(4, 1fr); } }
.stats li { padding: 28px 12px; text-align: center; border-left: 1px solid var(--line); }
.stats li:nth-child(odd) { border-left: 0; }
@media (min-width: 760px) { .stats li:nth-child(odd) { border-left: 1px solid var(--line); } .stats li:first-child { border-left: 0; } }
@media (max-width: 759px) { .stats li:nth-child(n+3) { border-top: 1px solid var(--line); } }
.stats b { display: block; font-size: clamp(2rem, 1.4rem + 2.4vw, 3rem); font-weight: 800; letter-spacing: -0.03em; line-height: 1.05; font-variant-numeric: tabular-nums; }
.stats li:nth-child(1) b { color: var(--teal); }
.stats li:nth-child(2) b { color: var(--orange); }
.stats li:nth-child(3) b { color: var(--blue); }
.stats span { color: var(--ink-2); font-size: var(--text-sm); font-weight: 500; }

/* ---------- Section chung ---------- */
.section { padding: var(--space-section) 0; }
.section-head { max-width: 760px; margin-bottom: clamp(2.5rem, 2rem + 2vw, 4rem); }
.section-head .kicker { font-size: var(--text-sm); font-weight: 800; letter-spacing: 0.12em; text-transform: uppercase; color: var(--orange); margin-bottom: 14px; display: block; }
.section-head h2 { font-size: var(--text-h2); }
.section-head p { font-size: var(--text-lead); color: var(--ink-2); margin: 18px 0 0; }
.section-alt { background: var(--paper-2); }

/* ---------- Danh sách cuộc thi ---------- */
.contests { padding: clamp(2.5rem, 2rem + 2vw, 4rem) 0; }
.contests-inner { display: grid; gap: 20px; align-items: center; }
@media (min-width: 900px) { .contests-inner { grid-template-columns: 250px 1fr; gap: 40px; } }
.contests h2 { font-size: var(--text-h3); }
.contests h2 small { display: block; font-size: var(--text-sm); color: var(--ink-3); font-weight: 500; letter-spacing: 0; margin-top: 6px; }
.contest-list { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: 10px; }
.contest-list li {
  border: 1.5px solid var(--line); background: var(--surface); border-radius: 12px;
  padding: 8px 14px; font-weight: 700; font-size: 0.95rem; letter-spacing: 0.01em; line-height: 1.25;
}
.contest-list li small { display: block; font-weight: 500; font-size: 0.75rem; color: var(--ink-3); letter-spacing: 0; }
.fineprint { font-size: 0.8rem; color: var(--ink-3); margin: 16px 0 0; }

/* ---------- Hàng tính năng (xen kẽ) ---------- */
.feature { display: grid; gap: clamp(2rem, 1.5rem + 3vw, 5rem); align-items: center; }
.feature + .feature { margin-top: var(--space-section); }
@media (min-width: 900px) {
  .feature { grid-template-columns: 1fr 1fr; }
  .feature.is-flipped .feature-media { order: 2; }
}
.feature-media { position: relative; display: grid; place-items: center; padding: clamp(24px, 4vw, 48px) 0; }
.feature-media::before { /* khối màu nền phía sau điện thoại */
  content: ""; position: absolute; inset: 0 6%; border-radius: var(--radius-lg); background: var(--tint, var(--teal-soft));
}
.feature-media .phone { width: min(78%, 320px); z-index: 1; }
.tint-teal { --tint: var(--teal-soft); } .tint-blue { --tint: var(--blue-soft); } .tint-orange { --tint: var(--orange-soft); }
.feature-media .phone.tilt-l { transform: rotate(-3deg); }
.feature-media .phone.tilt-r { transform: rotate(3deg); }
.feature-copy .step { display: inline-grid; place-items: center; width: 40px; height: 40px; border-radius: 12px; background: var(--ink); color: var(--paper); font-weight: 800; margin-bottom: 20px; font-variant-numeric: tabular-nums; }
.feature-copy h3 { font-size: clamp(1.6rem, 1.2rem + 1.6vw, 2.25rem); letter-spacing: -0.025em; }
.feature-copy > p { font-size: var(--text-lead); color: var(--ink-2); margin: 16px 0 24px; }
.ticks { list-style: none; padding: 0; margin: 0; display: grid; gap: 12px; }
.ticks li { display: grid; grid-template-columns: 24px 1fr; gap: 12px; align-items: start; }
.ticks li::before {
  content: ""; width: 24px; height: 24px; border-radius: 8px; margin-top: 1px;
  background: var(--teal-soft) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%230e7c70' stroke-width='3' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m6 12.5 4 4 8-9'/%3E%3C/svg%3E") center/16px no-repeat;
}
.ticks b { font-weight: 700; }

/* ---------- Bento "Thi thử" ---------- */
.bento { display: grid; gap: 16px; }
@media (min-width: 900px) { .bento { grid-template-columns: repeat(6, 1fr); grid-auto-rows: minmax(0, auto); gap: 20px; } }
.tile {
  position: relative; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-lg);
  padding: clamp(22px, 2.5vw, 32px); overflow: hidden; display: flex; flex-direction: column;
  transition: transform 300ms var(--ease-out), box-shadow 300ms var(--ease-out);
}
.tile:hover { transform: translateY(-4px); box-shadow: var(--shadow-sm); }
.tile h3 { font-size: var(--text-h3); margin-bottom: 10px; }
.tile p { color: var(--ink-2); margin: 0; }
.tile .phone { width: min(82%, 280px); margin: 28px auto -120px; }
.tile .phone img { box-shadow: var(--shadow-sm); }
.tile-note { margin-top: 12px !important; font-size: var(--text-sm); color: var(--ink-3) !important; }
.big-num .of { font-size: 0.45em; color: var(--ink-3); letter-spacing: -0.02em; }
.cta-gap { margin-top: clamp(3rem, 2rem + 4vw, 6rem); }
@media (min-width: 900px) {
  .tile-a { grid-column: span 3; grid-row: span 2; }
  .tile-b, .tile-c { grid-column: span 3; }
  .tile-d { grid-column: span 2; }
  .tile-e { grid-column: span 4; }
}
.tile-a { background: var(--ink); color: var(--paper); border-color: transparent; }
.tile-a p { color: color-mix(in srgb, var(--paper) 78%, transparent); }
.tile-a .phone { width: min(70%, 300px); margin-bottom: -170px; }
.tile-b { background: var(--orange-soft); border-color: transparent; }
.tile-c { background: var(--blue-soft); border-color: transparent; }
.tile-split { display: grid; gap: 20px; align-items: center; }
@media (min-width: 560px) { .tile-split { grid-template-columns: 1fr 190px; } .tile-split .phone { margin: 0 0 -140px; width: 100%; } }
.format-table { width: 100%; border-collapse: collapse; margin-top: 18px; font-size: var(--text-sm); font-variant-numeric: tabular-nums; }
.format-table th, .format-table td { text-align: left; padding: 9px 8px; border-top: 1px solid var(--line); vertical-align: top; }
.format-table th { color: var(--ink-3); font-weight: 600; font-size: 0.8rem; }
.format-table td:first-child { font-weight: 700; }
.pill { display: inline-block; font-size: 0.75rem; font-weight: 700; padding: 2px 8px; border-radius: 999px; background: var(--teal-soft); color: var(--teal); white-space: nowrap; }
.pill-warn { background: var(--orange-soft); color: color-mix(in srgb, var(--orange) 70%, var(--ink)); }
.big-num { font-size: clamp(3rem, 2rem + 4vw, 4.5rem); font-weight: 800; letter-spacing: -0.04em; line-height: 1; color: var(--teal); margin: 6px 0 12px; }

/* ---------- Phụ huynh yên tâm ---------- */
.trust { display: grid; gap: 1px; background: var(--line); border: 1px solid var(--line); border-radius: var(--radius-lg); overflow: hidden; }
@media (min-width: 640px) { .trust { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 1000px) { .trust { grid-template-columns: repeat(3, 1fr); } }
.trust > div { background: var(--surface); padding: 28px; }
.trust svg { width: 28px; height: 28px; color: var(--teal); margin-bottom: 14px; }
.trust h3 { font-size: 1.125rem; margin-bottom: 8px; letter-spacing: -0.01em; }
.trust p { color: var(--ink-2); margin: 0; font-size: 0.975rem; }

/* ---------- Các bước bắt đầu ---------- */
.steps { list-style: none; margin: 0; padding: 0; display: grid; gap: 28px; counter-reset: s; }
@media (min-width: 860px) { .steps { grid-template-columns: repeat(3, 1fr); gap: 32px; } }
.steps li { counter-increment: s; position: relative; padding-top: 64px; }
.steps li::before {
  content: counter(s, decimal-leading-zero); position: absolute; top: 0; left: 0;
  font-size: 2.75rem; font-weight: 800; letter-spacing: -0.04em; line-height: 1; color: transparent;
  -webkit-text-stroke: 1.5px var(--ink-3);
}
.steps li::after { content: ""; position: absolute; top: 22px; left: 80px; right: 0; height: 1.5px; background: repeating-linear-gradient(90deg, var(--line) 0 8px, transparent 8px 14px); }
.steps h3 { font-size: 1.25rem; margin-bottom: 8px; }
.steps p { color: var(--ink-2); margin: 0; }

/* ---------- FAQ ---------- */
.faq { display: grid; gap: 12px; max-width: 860px; }
.faq details { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); transition: border-color var(--duration-fast); }
.faq details[open] { border-color: color-mix(in srgb, var(--teal) 45%, var(--line)); }
.faq summary {
  list-style: none; cursor: pointer; padding: 18px 56px 18px 22px; font-weight: 700; position: relative; border-radius: var(--radius);
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after {
  content: ""; position: absolute; right: 20px; top: 50%; width: 22px; height: 22px; margin-top: -11px; border-radius: 50%;
  background: var(--paper-2) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%236b7090' stroke-width='2.5' stroke-linecap='round'%3E%3Cpath d='M12 6v12M6 12h12'/%3E%3C/svg%3E") center/14px no-repeat;
  transition: transform 250ms var(--ease-out);
}
.faq details[open] summary::after { transform: rotate(45deg); }
.faq details > div { padding: 0 22px 18px; color: var(--ink-2); }
.faq details > div p:last-child { margin: 0; }

/* ---------- CTA cuối trang ---------- */
.cta-band {
  position: relative; overflow: hidden; border-radius: var(--radius-lg); background: var(--teal); color: #fff;
  padding: clamp(2.5rem, 2rem + 3vw, 4.5rem) clamp(1.5rem, 1rem + 3vw, 4rem);
  display: grid; gap: 28px; align-items: center;
}
:root[data-theme="dark"] .cta-band { background: #0d5f56; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .cta-band { background: #0d5f56; } }
@media (min-width: 860px) { .cta-band { grid-template-columns: 1fr auto; } }
.cta-band h2 { font-size: var(--text-h2); color: #fff; }
.cta-band p { margin: 12px 0 0; color: rgb(255 255 255 / 0.86); font-size: var(--text-lead); }
.cta-band .owl { position: absolute; right: -30px; bottom: -40px; width: 200px; opacity: 0.16; pointer-events: none; }
@media (min-width: 860px) { .cta-band .owl { position: static; opacity: 1; width: 150px; justify-self: end; grid-row: span 2; } }
.cta-band .hero-actions { position: relative; }

/* ---------- Hỗ trợ ---------- */
.support-grid { display: grid; gap: 16px; }
@media (min-width: 760px) { .support-grid { grid-template-columns: 1fr 1fr; } }
.card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 24px; }
.card h3 { font-size: 1.125rem; margin-bottom: 10px; }
.card p:last-child, .card ol:last-child, .card ul:last-child { margin-bottom: 0; }
.card-mail { font-size: 1.125rem; font-weight: 700; word-break: break-all; }

/* ---------- Footer ---------- */
.site-footer { border-top: 1px solid var(--line); padding: 48px 0 40px; font-size: var(--text-sm); color: var(--ink-3); }
.site-footer .wrap { display: grid; gap: 28px; }
@media (min-width: 860px) { .site-footer .wrap { grid-template-columns: 1.4fr 1fr 1fr; } }
.site-footer h2 { font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.1em; color: var(--ink-2); margin-bottom: 12px; }
.site-footer ul { list-style: none; padding: 0; margin: 0; display: grid; gap: 8px; }
.site-footer a { color: var(--ink-2); text-decoration: none; }
.site-footer a:hover { color: var(--ink); text-decoration: underline; }
.site-footer .brand { margin-bottom: 12px; }
.site-footer .legal { grid-column: 1 / -1; border-top: 1px solid var(--line); padding-top: 20px; display: flex; flex-wrap: wrap; gap: 8px 24px; justify-content: space-between; }

/* ---------- Trang văn bản (chính sách, xoá tài khoản…) ---------- */
.page-head { padding: clamp(2.5rem, 2rem + 3vw, 5rem) 0 clamp(2rem, 1.5rem + 2vw, 3rem); border-bottom: 1px solid var(--line); }
.page-head .kicker { font-size: var(--text-sm); font-weight: 800; letter-spacing: 0.12em; text-transform: uppercase; color: var(--orange); display: block; margin-bottom: 12px; }
.page-head h1 { font-size: clamp(2rem, 1.5rem + 2.4vw, 3.25rem); letter-spacing: -0.03em; }
.page-head p { color: var(--ink-2); font-size: var(--text-lead); margin: 16px 0 0; max-width: 42em; }
.page-meta { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 20px; }
.page-meta span { font-size: 0.825rem; background: var(--surface); border: 1px solid var(--line); border-radius: 999px; padding: 4px 12px; color: var(--ink-2); }
.prose { max-width: 760px; padding-top: clamp(2rem, 1.5rem + 2vw, 3rem); }
.prose h2 { font-size: clamp(1.25rem, 1.1rem + 0.6vw, 1.5rem); margin: 2.5em 0 0.7em; letter-spacing: -0.015em; display: flex; gap: 12px; align-items: baseline; }
.prose h2 .n { color: var(--teal); font-variant-numeric: tabular-nums; }
.prose > h2:first-child, .prose > .card:first-child { margin-top: 0; }
.prose ul, .prose ol { padding-left: 1.3em; }
.prose li { margin: 0.4em 0; }
.prose li::marker { color: var(--teal); font-weight: 700; }
.table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); margin: 1em 0; }
.table-wrap table { border-collapse: collapse; width: 100%; min-width: 520px; font-size: 0.95rem; }
.table-wrap th, .table-wrap td { text-align: left; vertical-align: top; padding: 12px 16px; border-top: 1px solid var(--line); }
.table-wrap th { background: var(--paper-2); border-top: 0; font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.06em; color: var(--ink-3); }
.callout { border-left: 4px solid var(--teal); background: var(--teal-soft); border-radius: 0 var(--radius-sm) var(--radius-sm) 0; padding: 14px 18px; margin: 1.2em 0; }
.callout p:last-child { margin: 0; }
.option-grid { display: grid; gap: 16px; }
@media (min-width: 760px) { .option-grid { grid-template-columns: 1fr 1fr; } }
.option-grid .card { position: relative; }
.option-grid .tag { display: inline-block; font-size: 0.75rem; font-weight: 800; letter-spacing: 0.06em; text-transform: uppercase; padding: 3px 10px; border-radius: 999px; background: var(--teal-soft); color: var(--teal); margin-bottom: 12px; }
.option-grid .card:nth-child(2) .tag { background: var(--blue-soft); color: var(--blue); }
.center-page { min-height: calc(100vh - 220px); display: grid; place-items: center; text-align: center; padding: 64px 0; }
.center-page img { width: 150px; margin: 0 auto 24px; }
.center-page h1 { font-size: clamp(1.9rem, 1.5rem + 2vw, 2.75rem); }
.center-page p { color: var(--ink-2); font-size: var(--text-lead); max-width: 32em; margin: 16px auto 0; }
.center-page .hero-actions { justify-content: center; margin-top: 28px; }

/* ---------- Chuyển động xuất hiện (tắt khi giảm chuyển động) ---------- */
.js .reveal { opacity: 0; transform: translateY(24px); transition: opacity var(--duration) var(--ease-out), transform var(--duration) var(--ease-out); }
.js .reveal.is-visible { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .js .reveal { opacity: 1; transform: none; transition: none; }
  .btn, .tile, .btn svg { transition: none; }
}