/* =====================================================
   Khách Khoá thông minh - phiếu khảo sát #4
   Bản nháp HTML/CSS tĩnh. Chưa deploy, chưa có khách duyệt.
   Quy tắc bắt buộc: mọi màu và font khai token tại :root.
   Hai hướng màu theo mục 5.2 của thiet-ke.md, kích hoạt qua
   data-theme="A" (thép) hoặc data-theme="B" (retail) trên <html>.
   ===================================================== */

:root {
  /* Font: đề xuất Be Vietnam Pro (Google Fonts), CHỜ KHÁCH duyệt font */
  --font-sans: "Be Vietnam Pro", -apple-system, "Segoe UI", Roboto, Arial, sans-serif;

  /* Thước chữ theo mục 5.3 */
  --fs-body: 1.0625rem;      /* 17px */
  --fs-small: 0.9375rem;     /* 15px */
  --fs-h3: 1.375rem;         /* 22px */
  --fs-h2: 1.75rem;          /* 28px */
  --fs-h1: clamp(1.75rem, 4.5vw, 2.5rem); /* 28-40px theo mục 5.3 */
  --line-height: 1.5;
  --fs-phone: 1.5rem;

  /* Nhịp không gian theo mục 5.3 */
  --space-section: clamp(2rem, 5vw, 4rem); /* 32-64px */
  --space-gap: 1.25rem;
  --page-max: 1200px;
  --page-pad: clamp(1rem, 2.5vw, 1.5rem);  /* 16-24px */
  --radius: 10px;            /* bo góc nhỏ 8-12px */

  /* Chiều cao thanh trên (64-72px) và nhóm nút nổi (mục 4.2) */
  --header-h: 4.25rem;       /* 68px */
  --fab-size: 3.5rem;        /* 56px */
  --fab-size-sm: 3rem;       /* 48px dưới 480px */
  --fab-gap: 0.75rem;
  --z-fab: 90;
  --z-header: 80;
  --z-menu: 100;             /* menu mobile cao hơn nút nổi */
  --z-chat: 85;              /* bong bóng chat dưới nhóm nút nổi */
}

/* Hướng A - thep: nền xám trắng ấm, chữ xanh đen, nhấn xanh thép (mục 5.2.1.1) */
[data-theme="A"] {
  --bg-page: #f7f6f3;
  --bg-surface: #ffffff;
  --bg-muted: #edecea;
  --ink: #17242b;
  --ink-soft: #44545e;
  --accent: #1d6a80;
  --accent-strong: #155468;
  --on-accent: #ffffff;
  --border: #d9d6d0;
  --field: #ffffff;
  --danger: #a33a2e;
  --danger-soft: #fbeae7;
  --ok-soft: #e9f2ec;
  --ok: #2c6e49;
}

/* Hướng B - retail: nền trắng, chữ đen, nhấn đỏ gạch (mục 5.2.1.2) */
[data-theme="B"] {
  --bg-page: #ffffff;
  --bg-surface: #ffffff;
  --bg-muted: #f1f1f1;
  --ink: #111111;
  --ink-soft: #474747;
  --accent: #b23a2a;
  --accent-strong: #962f22;
  --on-accent: #ffffff;
  --border: #dcdcdc;
  --field: #ffffff;
  --danger: #a33a2e;
  --danger-soft: #fbeae7;
  --ok-soft: #e9f2ec;
  --ok: #2c6e49;
}

/* ===== Nền chung ===== */
*, *::before, *::after { box-sizing: border-box; }

[hidden] { display: none !important; }

html {
  overflow-x: clip;
  scroll-padding-top: calc(var(--header-h) + 1rem);
}

body {
  margin: 0;
  overflow-x: clip;
  background: var(--bg-page);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: var(--fs-body);
  line-height: var(--line-height);
}

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

a { color: var(--accent); }

h1, h2, h3 { line-height: 1.25; margin: 0 0 .6em; }
h1 { font-size: var(--fs-h1); }
h2 { font-size: var(--fs-h2); }
h3 { font-size: var(--fs-h3); }
p { margin: 0 0 1em; }

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* Link bỏ qua tới nội dung chính: chỉ hiện khi focus */
.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 200;
  background: var(--bg-surface);
  color: var(--ink);
  padding: .6rem 1rem;
}
.skip:focus { left: 0; }

/* Cấm tràn ngang: lưới chứa ảnh dùng minmax(0, 1fr) */
.grid {
  display: grid;
  gap: var(--space-gap);
  grid-template-columns: repeat(auto-fill, minmax(min(16rem, 100%), 1fr));
}
.grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
/* Lưới sản phẩm: 3 cột desktop, 2 cột mobile theo mục 6.2.4 */
.grid.sp-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }

/* ===== Bề mặt ===== */
.surface {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
}
.muted { color: var(--ink-soft); }
.giu-cho { color: var(--ink-soft); font-style: italic; }
.gia { font-weight: 700; }

.dien {
  background: var(--bg-muted);
  border-radius: var(--radius);
  padding: 1.25rem;
  margin: 0 0 1.25rem;
}

/* ===== Thanh trên (mục 4.1) ===== */
.site-header {
  position: sticky;
  top: 0;
  z-index: var(--z-header);
  background: var(--bg-surface);
  min-height: var(--header-h);
  display: flex;
  align-items: center;
}
.site-header .in {
  width: 100%;
  max-width: var(--page-max);
  margin: 0 auto;
  padding: 0 var(--page-pad);
  display: flex;
  align-items: center;
  gap: 1rem;
}
.brand { font-weight: 700; text-decoration: none; color: var(--ink); font-size: 1.05rem; }
.brand .giu-cho { font-size: var(--fs-small); display: block; font-weight: 400; }

.main-nav { margin-left: auto; }
.main-nav ul { display: flex; gap: 1.25rem; list-style: none; margin: 0; padding: 0; }
.main-nav a { text-decoration: none; color: var(--ink); font-size: var(--fs-small); font-weight: 500; }
.main-nav a:hover { color: var(--accent); }
.main-nav a[aria-current="page"] { color: var(--accent); }

.header-cta { display: flex; align-items: center; gap: .75rem; margin-left: 1rem; }
.hotline { font-weight: 700; color: var(--ink); text-decoration: none; font-size: 1.05rem; white-space: nowrap; }

/* Nút mở menu mobile: ẩn khi >= 1024px */
.nav-toggle { display: none; }

/* ===== Nút (mục 5.4.1) ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: .5rem;
  min-height: 44px;
  padding: .55rem 1.1rem;
  border-radius: var(--radius);
  border: 1px solid transparent;
  font: inherit;
  font-size: var(--fs-small);
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  transition: background-color .2s, color .2s, border-color .2s, transform .1s, opacity .2s;
}
.btn-primary { background: var(--accent); color: var(--on-accent); }
.btn-primary:hover { background: var(--accent-strong); }
.btn-primary:active { transform: scale(0.98); }
.btn-outline { background: transparent; color: var(--accent); border-color: var(--accent); }
.btn-outline:hover { background: var(--accent); color: var(--on-accent); }
.btn-outline:active { transform: scale(0.98); }
.btn:disabled { opacity: .5; cursor: not-allowed; transform: none; }
.btn-sm { min-height: 40px; padding: .4rem .8rem; }

/* ===== Khối hero ===== */
.hero { padding: var(--space-section) 0; }
.hero-media { margin: 0 0 1.25rem; }
.hero-media img { width: 100%; border-radius: var(--radius); display: block; }
.hero-actions { display: flex; flex-wrap: wrap; gap: .75rem; }
.hero-media figcaption { font-size: var(--fs-small); color: var(--ink-soft); margin-top: .4rem; }

/* ===== Thẻ nhóm sản phẩm (mục 6.1.2) ===== */
.nhom-card img { width: 100%; border-radius: var(--radius); display: block; }
.nhom-card h3 { margin: .75rem 0 .25rem; }
.nhom-card a { text-decoration: none; color: inherit; display: block; }
.nhom-card a:hover h3 { color: var(--accent); }

/* Thẻ sản phẩm (mục 6.2.2): ảnh vuông 1:1 */
.product-card img { width: 100%; aspect-ratio: 1 / 1; object-fit: cover; border-radius: var(--radius); display: block; }
.product-card h3 { margin: .6rem 0 .2rem; font-size: 1.05rem; }
.product-card .gia { margin: 0 .25rem .6rem 0; }
.product-card form { display: flex; gap: .5rem; flex-wrap: wrap; }

/* ===== Bộ lọc chip (mục 6.2.1) ===== */
.chips { display: flex; flex-wrap: wrap; gap: .5rem; margin: 0 0 1.5rem; }
.chip {
  border: 1px solid var(--border);
  background: var(--bg-surface);
  color: var(--ink);
  border-radius: 999px;
  padding: .45rem 1rem;
  font: inherit;
  font-size: var(--fs-small);
  cursor: pointer;
}
.chip[aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: var(--on-accent); }

/* ===== Khối video (mục 6.1.6) ===== */
.video-box { position: relative; }
.video-box .khung-video { width: 100%; aspect-ratio: 16 / 9; border: 0; border-radius: var(--radius); background: var(--bg-muted); display: block; }

/* ===== Dải nhãn hàng dạng chữ (mục 6.1.3) ===== */
.nhan-hang { display: flex; flex-wrap: wrap; gap: .5rem; list-style: none; padding: 0; margin: 0; }
.nhan-hang li {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: .5rem .9rem;
  font-size: var(--fs-small);
  font-weight: 600;
  background: var(--bg-surface);
}

/* ===== Quy trình 4 bước (mục 6.3.3) ===== */
.quy-trinh { display: grid; gap: var(--space-gap); grid-template-columns: repeat(4, minmax(0, 1fr)); list-style: none; padding: 0; margin: 0; }
.quy-trinh .buoc { display: block; font-weight: 700; color: var(--accent); margin-bottom: .3rem; }

/* ===== Lưới hình ảnh lắp đặt (mục 6.4) ===== */
.gallery { display: grid; gap: var(--space-gap); grid-template-columns: repeat(3, minmax(0, 1fr)); }
.gallery figure { margin: 0; }
.gallery img { width: 100%; border-radius: var(--radius); display: block; object-fit: cover; aspect-ratio: 4 / 3; }
.gallery figcaption { font-size: var(--fs-small); color: var(--ink-soft); margin-top: .35rem; }

/* ===== Bảng thông số trang chi tiết (mục 6.2.3) ===== */
.bang-thong-so { width: 100%; border-collapse: collapse; }
.bang-thong-so caption { text-align: left; margin-bottom: .5rem; }
.bang-thong-so th, .bang-thong-so td {
  text-align: left;
  padding: .4rem .5rem;
  border-bottom: 1px solid var(--border);
}

/* ===== Form (mục 6.6 và 5.4.2): nhãn luôn hiển thị ===== */
.form-card { max-width: 40rem; }
.field { display: block; margin-bottom: 1rem; }
.field > span {
  display: block;
  font-size: var(--fs-small);
  font-weight: 600;
  margin-bottom: .3rem;
}
.field input, .field select, .field textarea {
  width: 100%;
  padding: .6rem .75rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--field);
  color: var(--ink);
  font: inherit;
  font-size: 1rem;
}
.field textarea { min-height: 6rem; resize: vertical; }
.field .err {
  display: none;
  color: var(--danger);
  font-size: var(--fs-small);
  margin-top: .25rem;
}
.field.invalid input, .field.invalid select, .field.invalid textarea { border-color: var(--danger); }
.field.invalid .err { display: block; }
.check { display: flex; gap: .5rem; align-items: flex-start; font-size: var(--fs-small); }
.check input { margin-top: .2rem; }
.form-actions { display: flex; align-items: center; gap: .75rem; flex-wrap: wrap; }
.spinner {
  width: 1rem; height: 1rem; border-radius: 50%;
  border: 2px solid var(--on-accent);
  border-top-color: transparent;
  display: none;
  animation: quay 0.8s linear infinite;
}
.btn.is-busy .spinner { display: inline-block; }
@keyframes quay { to { transform: rotate(360deg); } }

.form-status { margin: 1rem 0; padding: 1rem; border-radius: var(--radius); }
.form-status p { margin: 0; }
.form-status .hotline-lai { font-weight: 700; }
.form-status[data-kind="ok"] { background: var(--ok-soft); color: var(--ok); }
.form-status[data-kind="loi"] { background: var(--danger-soft); color: var(--danger); }

.form-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0 1rem; }
.form-grid .field-full { grid-column: 1 / -1; }

/* ===== Liên hệ 2 cột (mục 6.5) ===== */
.contact-cols { display: grid; grid-template-columns: minmax(0, 2fr) minmax(0, 3fr); gap: calc(var(--space-gap) * 2); }
.phone-big { font-size: var(--fs-phone); font-weight: 800; color: var(--ink); text-decoration: none; display: inline-block; }
.contact-cols dt { font-weight: 700; margin-top: .9rem; }
.contact-cols dd { margin: .1rem 0 0; }

/* ===== Nút nổi Gọi/Zalo/Messenger (mục 4.2) ===== */
.fab {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  z-index: var(--z-fab);
  display: flex;
  flex-direction: column;
  gap: var(--fab-gap);
  align-items: center;
}
.fab a {
  width: var(--fab-size);
  height: var(--fab-size);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  font-size: var(--fs-small);
  font-weight: 700;
  border: 2px solid var(--bg-surface);
  transition: transform .1s, filter .2s;
}
.fab a:active { transform: scale(0.96); }
.fab .goi { background: var(--accent); color: var(--on-accent); }
.fab .zalo { background: #0068ff; color: #ffffff; }
.fab .mess { background: #a334fa; color: #ffffff; }
.fab a:hover { filter: brightness(0.9); }

/* ===== Bong bóng chat tự động (mục 4.3) ===== */
.chat {
  position: fixed;
  right: 1rem;
  bottom: calc(1rem + var(--fab-size) * 3 + var(--fab-gap) * 3 + 0.75rem);
  z-index: var(--z-chat);
  width: min(20rem, calc(100vw - 2rem));
}
.chat-bubble {
  width: 3.25rem;
  height: 3.25rem;
  border-radius: 50%;
  border: 2px solid var(--bg-surface);
  background: var(--accent);
  color: var(--on-accent);
  font-size: var(--fs-small);
  font-weight: 700;
  cursor: pointer;
  margin-left: auto;
  display: block;
  transition: transform .1s, filter .2s;
}
.chat-bubble:active { transform: scale(0.96); }
.chat-bubble:hover { filter: brightness(0.9); }
.chat-panel {
  position: relative;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 12px 32px rgba(0, 0, 0, .18);
  padding: 1rem;
  margin-bottom: .6rem;
}
.chat-panel h2 { font-size: 1.1rem; margin-bottom: .35rem; }
.chat-note { margin-top: .6rem; font-size: var(--fs-small); }
.chat-note strong { color: var(--accent); }
.chat-note .btn { margin-right: .4rem; }
.chat-close {
  position: absolute;
  top: .4rem;
  right: .4rem;
  border: 0;
  background: transparent;
  font-size: 1.1rem;
  line-height: 1;
  min-width: 44px;
  min-height: 44px;
  cursor: pointer;
  color: var(--ink-soft);
}

/* ===== Khối liên hệ cuối trang (mục 6.1.7) ===== */
.lien-he-cuoi { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: var(--space-gap); align-items: start; }
.lien-he-cuoi .phone-big { margin-bottom: .5rem; }
.form-mini input {
  width: 100%;
  padding: .6rem .75rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font: inherit;
  background: var(--field);
  color: var(--ink);
}

/* ===== Footer ===== */
.site-footer {
  border-top: 1px solid var(--border);
  margin-top: var(--space-section);
  padding: var(--space-section) 0;
  background: var(--bg-surface);
}
.site-footer .in { max-width: var(--page-max); margin: 0 auto; padding: 0 var(--page-pad); }
.site-footer p { margin: 0 0 .35rem; }

/* ===== Khung trang ===== */
.wrap { max-width: var(--page-max); margin: 0 auto; padding: 0 var(--page-pad); }
section { padding-top: var(--space-section); }
section:first-of-type { padding-top: 0; }
.page-title { padding: var(--space-section) 0 0; }
.page-hero { padding: var(--space-section) 0; }

/* ===== Mobile < 1024px (mục 4.1.3): menu trượt từ phải ===== */
@media (max-width: 1023.98px) {
  .header-cta .btn { display: none; } /* giữ logo, hotline và nút mở menu */

  .nav-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 44px;
    min-height: 44px;
    margin-left: auto;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    background: var(--bg-surface);
    color: var(--ink);
    font: inherit;
    font-weight: 700;
    cursor: pointer;
  }
  .header-cta { margin-left: 0; }

  .main-nav {
    position: fixed;
    inset: 0 0 0 auto;
    width: min(20rem, 85vw);
    background: var(--bg-surface);
    z-index: var(--z-menu);
    padding: 1rem;
    transform: translateX(100%);
    visibility: hidden;
    transition: transform .25s ease, visibility 0s .25s;
    box-shadow: -12px 0 32px rgba(0, 0, 0, .15);
  }
  .main-nav.open { transform: translateX(0); visibility: visible; transition: transform .25s ease; }
  .main-nav ul { flex-direction: column; gap: .25rem; margin-top: 3rem; }
  .main-nav a { display: block; padding: .75rem .5rem; font-size: 1.05rem; }
  .nav-close {
    position: absolute;
    top: .75rem;
    right: .75rem;
    border: 1px solid var(--border);
    background: var(--bg-surface);
    border-radius: var(--radius);
    min-width: 44px;
    min-height: 44px;
    font-size: 1.2rem;
    cursor: pointer;
    color: var(--ink);
  }
  body.nav-lock { overflow: hidden; }

  .contact-cols { grid-template-columns: 1fr; }
  .lien-he-cuoi { grid-template-columns: 1fr; }
  .quy-trinh { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .gallery { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid-4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid.sp-3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .form-grid { grid-template-columns: 1fr; }
}

/* ===== Màn dưới 480px (mục 4.2.2): nút nổi thu 48px ===== */
@media (max-width: 479.98px) {
  .fab a { width: var(--fab-size-sm); height: var(--fab-size-sm); }
  .chat {
    bottom: calc(1rem + var(--fab-size-sm) * 3 + var(--fab-gap) * 3 + 0.75rem);
  }
  .grid-2 { grid-template-columns: 1fr; }
}

/* ===== Giảm chuyển động (mục 5.4.3) ===== */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}