/* KTSPdf — exercise-book themed landing page
   Fonts: Hind Siliguri (body), Noto Serif Bengali (headings) */

:root {
  --font-body: "Hind Siliguri", "Noto Sans Bengali", system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-head: "Noto Serif Bengali", "Hind Siliguri", Georgia, serif;

  --paper: #fffbef;
  --paper-2: #fff6e0;
  --card: #ffffff;
  --ink: #23303d;
  --ink-soft: #5c6b7a;
  --rule: rgba(47, 90, 140, .13);
  --margin-line: #e05a4f;
  --hl-yellow: #ffe27a;
  --hl-green: #b6ecc4;
  --hl-pink: #ffc7d9;
  --accent: #14664c;
  --accent-ink: #ffffff;
  --border: rgba(35, 48, 61, .16);
  --shadow: 0 1px 2px rgba(35, 48, 61, .08), 0 6px 16px rgba(35, 48, 61, .07);
  --focus: #0b57d0;

  --rule-gap: 34px;
  --radius: 14px;
  --tap: 48px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --paper: #161a1e;
    --paper-2: #1c2126;
    --card: #22282e;
    --ink: #edf1f5;
    --ink-soft: #a9b4c0;
    --rule: rgba(150, 180, 220, .10);
    --margin-line: #f0776b;
    --hl-yellow: #6b5c14;
    --hl-green: #1e4b34;
    --hl-pink: #5a2338;
    --accent: #4fd39c;
    --accent-ink: #0d1a14;
    --border: rgba(237, 241, 245, .16);
    --shadow: 0 1px 2px rgba(0, 0, 0, .5), 0 8px 22px rgba(0, 0, 0, .35);
    --focus: #8ec5ff;
  }
}

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

[hidden] { display: none !important; }

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

body {
  margin: 0;
  font-family: var(--font-body);
  font-size: 17px;
  line-height: 1.7;
  color: var(--ink);
  background: var(--paper);
  overflow-x: hidden;
}

h1, h2, h3 {
  font-family: var(--font-head);
  line-height: 1.35;
  margin: 0 0 .5em;
  font-weight: 700;
}

h1 { font-size: clamp(1.9rem, 8vw, 2.7rem); }
h2 { font-size: clamp(1.4rem, 5.5vw, 1.9rem); }
h3 { font-size: 1.12rem; font-family: var(--font-body); font-weight: 700; }

p { margin: 0 0 1rem; }

a { color: var(--accent); text-decoration-thickness: 1px; text-underline-offset: 3px; }

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

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

:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 3px;
  border-radius: 6px;
}

/* ---------- layout helpers ---------- */

.wrap { width: 100%; max-width: 760px; margin-inline: auto; padding-inline: 20px; }

.section { padding-block: clamp(40px, 9vw, 72px); }
.section-alt { background: var(--paper-2); }

.section-title { position: relative; display: inline-block; }
.section-title::after {
  content: "";
  position: absolute; left: 0; bottom: -.12em;
  width: 100%; height: .38em;
  background: var(--hl-yellow);
  z-index: -1;
  opacity: .85;
}

.section-hint { color: var(--ink-soft); font-size: 1rem; margin-top: -.2rem; }

.skip-link {
  position: absolute; left: 12px; top: -200px;
  background: var(--card); color: var(--ink);
  padding: 12px 18px; border-radius: 10px; box-shadow: var(--shadow);
  z-index: 50; transition: top .15s ease;
}
.skip-link:focus { top: 12px; }

/* ---------- ruled-paper surface ---------- */

.paper {
  position: relative;
  background-color: var(--paper);
  background-image:
    repeating-linear-gradient(to bottom, transparent 0 calc(var(--rule-gap) - 1px), var(--rule) calc(var(--rule-gap) - 1px) var(--rule-gap)),
    linear-gradient(to right, transparent 0 26px, var(--margin-line) 26px 28px, transparent 28px);
  background-size: 100% var(--rule-gap), 100% 100%;
  background-repeat: repeat-y, no-repeat;
  background-position: 0 0, 0 0;
}
.paper > .wrap { padding-left: 42px; }

@media (min-width: 700px) {
  .paper { background-image:
      repeating-linear-gradient(to bottom, transparent 0 calc(var(--rule-gap) - 1px), var(--rule) calc(var(--rule-gap) - 1px) var(--rule-gap)),
      linear-gradient(to right, transparent 0 calc(50vw - 380px + 26px), var(--margin-line) calc(50vw - 380px + 26px) calc(50vw - 380px + 28px), transparent calc(50vw - 380px + 28px)); }
  /* .wrap is already centered by max-width 760px, so only a relative padding belongs here;
     using 50vw here collapsed the text column to almost nothing */
  .paper > .wrap { padding-left: 46px; }
}

/* ---------- header ---------- */

.site-header {
  position: sticky; top: 0; z-index: 20;
  background: var(--paper);
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: blur(6px);
  border-bottom: 1px solid var(--border);
}
.header-inner { display: flex; align-items: center; gap: 10px; min-height: 62px; }
.brand-icon { border-radius: 10px; flex: none; }
.brand-name { font-family: var(--font-head); font-weight: 700; font-size: 1.05rem; margin-inline-end: auto; }

.lang-toggle {
  font: inherit; font-weight: 600; font-size: .92rem;
  min-height: var(--tap); min-width: var(--tap); padding: 8px 16px;
  color: var(--ink); background: var(--card);
  border: 1.5px solid var(--border); border-radius: 999px;
  cursor: pointer;
}
.lang-toggle:hover { border-color: var(--accent); }

/* ---------- hero ---------- */

.hero { padding-block: clamp(32px, 7vw, 56px) clamp(40px, 8vw, 64px); }
.hero-tagline { font-size: 1.14rem; max-width: 34ch; color: var(--ink); }

.cta-block { margin: 26px 0 14px; }

.btn-download {
  display: inline-flex; align-items: center; justify-content: center; gap: 10px;
  min-height: 58px; padding: 14px 26px;
  font: inherit; font-size: 1.16rem; font-weight: 700;
  color: var(--accent-ink); background: var(--accent);
  border: 0; border-radius: 14px; box-shadow: var(--shadow);
  text-decoration: none; cursor: pointer;
  width: 100%; max-width: 420px;
}
.btn-download:hover { filter: brightness(1.06); text-decoration: none; }
.btn-download svg { flex: none; }

.release-meta {
  display: flex; flex-wrap: wrap; gap: 8px 10px;
  margin-top: 14px; font-size: .95rem; color: var(--ink-soft);
}
.release-meta li {
  background: var(--card); border: 1px solid var(--border);
  border-radius: 999px; padding: 5px 14px;
}
.release-meta b { color: var(--ink); font-weight: 600; }

/* APK এখনো আপলোড হয়নি — লাল সীমারেখার সতর্কবার্তা */
.release-meta .pending {
  background: var(--card); border: 1px solid var(--margin-line);
  border-radius: 10px; padding: 8px 14px; width: 100%;
  color: var(--margin-line); font-weight: 600; font-size: .95rem;
}

.btn-download.is-disabled {
  opacity: .55; cursor: not-allowed; box-shadow: none;
  filter: saturate(.6);
}

.trust-note { font-size: .95rem; color: var(--ink-soft); margin: 6px 0 0; }

/* ---------- notices / QR ---------- */

.notice {
  margin-top: 22px; padding: 16px 18px;
  background: var(--card);
  border: 1px solid var(--border);
  border-inline-start: 5px solid var(--margin-line);
  border-radius: var(--radius);
}
.notice-info { border-inline-start-color: var(--accent); }
.notice-text { margin: 0 0 12px; }

.qr-box { display: flex; align-items: center; gap: 16px; flex-wrap: wrap; }
#qr-canvas {
  width: 148px; height: 148px; flex: none;
  background: #fff; border: 1px solid var(--border); border-radius: 10px;
  image-rendering: pixelated;
}
.qr-url {
  font-family: ui-monospace, "Cascadia Mono", Consolas, monospace;
  font-size: .82rem; color: var(--ink-soft);
  word-break: break-all; max-width: 300px;
}

/* ---------- features ---------- */

.feature-list { display: grid; gap: 14px; margin-top: 26px; }
.feature {
  display: flex; gap: 14px; align-items: flex-start;
  background: var(--card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px;
  box-shadow: var(--shadow);
}
.feature h3 { margin: 0 0 4px; }
.feature p { margin: 0; color: var(--ink-soft); font-size: 1rem; }
.feature-icon {
  flex: none; width: 44px; height: 44px; border-radius: 12px;
  display: grid; place-items: center;
  background: var(--hl-green); color: var(--accent-ink);
}
.feature-icon svg { width: 24px; height: 24px; }
.feature:nth-child(2) .feature-icon { background: var(--hl-yellow); }
.feature:nth-child(4) .feature-icon { background: var(--hl-pink); }

@media (min-width: 700px) {
  .feature-list { grid-template-columns: 1fr 1fr; }
  .feature:nth-child(5) { grid-column: 1 / -1; }
}

/* ---------- screenshots ---------- */

.shot-rail {
  display: flex; gap: 14px;
  overflow-x: auto; overscroll-behavior-x: contain;
  -webkit-overflow-scrolling: touch;
  scroll-snap-type: x proximity;
  padding: 18px 20px 26px;
  max-width: 100vw;
}
.shot { flex: none; scroll-snap-align: center; }
.shot img {
  display: block;
  width: 190px; aspect-ratio: 360 / 780; height: auto;
  border-radius: 18px; border: 1px solid var(--border);
  background: var(--card); box-shadow: var(--shadow);
}
/* .shot-rail .wrap-এর বাইরে পুরো প্রস্থে থাকে, তাই এখানে 50vw ঠিক আছে */
@media (min-width: 700px) {
  .shot-rail { padding-inline: max(20px, calc(50vw - 380px + 20px)); }
  .shot img { width: 220px; }
}

/* ---------- install steps ---------- */

.steps { counter-reset: step; margin: 26px 0 0; display: grid; gap: 18px; }
.step { position: relative; padding-inline-start: 56px; }
.step::before {
  counter-increment: step; content: counter(step);
  position: absolute; inset-inline-start: 0; top: 2px;
  width: 42px; height: 42px; border-radius: 50%;
  display: grid; place-items: center;
  font-family: var(--font-head); font-size: 1.2rem; font-weight: 700;
  color: var(--ink); background: var(--hl-yellow);
  border: 2px solid var(--margin-line);
}
.step p { margin: 0; color: var(--ink-soft); }

/* ---------- changelog ---------- */

.changelog { display: grid; gap: 14px; margin-top: 22px; }
.log-item {
  background: var(--card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px 18px;
}
.log-head { display: flex; flex-wrap: wrap; gap: 4px 12px; align-items: baseline; margin: 0 0 8px; }
.log-ver { font-family: var(--font-head); font-weight: 700; font-size: 1.08rem; }
.log-date { color: var(--ink-soft); font-size: .9rem; }
.log-body { margin: 0; font-size: 1rem; color: var(--ink); white-space: pre-wrap; }
.log-body :is(ul, li) { margin: 0; }
.log-body p { margin: 0 0 .4em; }

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

.faq-list { display: grid; gap: 12px; margin-top: 24px; }
.faq {
  background: var(--card); border: 1px solid var(--border);
  border-radius: var(--radius); overflow: hidden;
}
.faq summary {
  list-style: none; cursor: pointer;
  display: flex; align-items: center; gap: 12px;
  min-height: var(--tap); padding: 14px 18px;
  font-weight: 600;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after {
  content: ""; flex: none; margin-inline-start: auto;
  width: 10px; height: 10px;
  border-right: 2.5px solid var(--ink-soft); border-bottom: 2.5px solid var(--ink-soft);
  transform: rotate(45deg); transition: transform .18s ease;
}
.faq[open] summary::after { transform: rotate(-135deg); }
.faq[open] summary { border-bottom: 1px dashed var(--border); }
.faq > p { padding: 14px 18px; margin: 0; color: var(--ink-soft); }

/* ---------- footer ---------- */

.site-footer { margin-top: 20px; border-top: 1px solid var(--border); padding-block: 34px 20px; }
.footer-inner { display: grid; gap: 22px; }
.footer-about { color: var(--ink-soft); margin: 0; }
.footer-h { font-size: 1rem; font-family: var(--font-body); margin: 0 0 6px; }
.footer-links { display: grid; gap: 2px; }
.footer-links a {
  display: inline-flex; align-items: center; min-height: var(--tap);
  color: var(--ink); text-decoration: underline;
}
.footer-links a:hover { color: var(--accent); }
.footer-bottom { margin-top: 18px; padding-top: 14px; border-top: 1px dashed var(--border); }
.footer-bottom p { margin: 0; font-size: .92rem; color: var(--ink-soft); }

@media (min-width: 700px) {
  .footer-inner { grid-template-columns: 1.4fr 1fr 1fr; align-items: start; }
}

/* ---------- simple text pages (privacy / disclaimer) ---------- */

.page-body { padding-block: 30px 60px; }
.page-body h1 { margin-bottom: .3em; }
.page-body h2 { margin-top: 1.8em; font-size: 1.2rem; }
.page-body p, .page-body li { max-width: 68ch; }
.page-body ul { list-style: disc; padding-inline-start: 22px; display: grid; gap: 6px; }
.back-link { display: inline-flex; align-items: center; min-height: var(--tap); }

/* In-page two-language blocks (privacy / disclaimer): CSS selects the visible language */
html[lang="bn"] .page-body [lang="en"] { display: none; }
html[lang="en"] .page-body [lang="bn"] { display: none; }

/* ---------- motion preference ---------- */

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    transition-duration: .01ms !important;
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
  }
}