/* ------------------------------------------------------------
   OCR A-Level Computer Science Hub
   Themes: light, dark, ocean, matrix (set on <html data-theme>)
   ------------------------------------------------------------ */

:root {
  --font: "Segoe UI", Inter, system-ui, -apple-system, Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: "Cascadia Code", "JetBrains Mono", Consolas, "SFMono-Regular", Menlo, monospace;
  --radius: 16px;
  --radius-sm: 10px;
  --ease: cubic-bezier(.2,.8,.2,1);
  --maxw: 1180px;
}

[data-theme="light"] {
  --bg: #f5f7fb;
  --bg-alt: #eef1f7;
  --surface: #ffffff;
  --surface-2: #f3f5fa;
  --text: #121826;
  --muted: #5b6474;
  --border: #e3e7ef;
  --accent: #0ea5e9;
  --accent-2: #f97316;
  --accent-text: #ffffff;
  --ok: #16a34a;
  --shadow: 0 10px 30px rgba(18, 24, 38, .08);
  --shadow-hover: 0 18px 40px rgba(14, 165, 233, .18);
  --hero-grad: linear-gradient(135deg, #e8f4ff 0%, #f5f7fb 60%, #fff3e8 100%);
  --rain: rgba(14, 165, 233, .35);
}

[data-theme="dark"] {
  --bg: #0f1420;
  --bg-alt: #121929;
  --surface: #182033;
  --surface-2: #1f2940;
  --text: #eef2f9;
  --muted: #9aa5ba;
  --border: #273149;
  --accent: #38bdf8;
  --accent-2: #fb923c;
  --accent-text: #0b1220;
  --ok: #34d399;
  --shadow: 0 10px 30px rgba(0, 0, 0, .35);
  --shadow-hover: 0 18px 40px rgba(56, 189, 248, .22);
  --hero-grad: linear-gradient(135deg, #0f1420 0%, #141c2e 60%, #1b1a2a 100%);
  --rain: rgba(56, 189, 248, .35);
}

[data-theme="ocean"] {
  --bg: #061a2b;
  --bg-alt: #072036;
  --surface: #0b2a44;
  --surface-2: #0f3553;
  --text: #e6f4ff;
  --muted: #8fb3cc;
  --border: #174363;
  --accent: #2dd4bf;
  --accent-2: #fbbf24;
  --accent-text: #04202a;
  --ok: #4ade80;
  --shadow: 0 10px 30px rgba(0, 0, 0, .4);
  --shadow-hover: 0 18px 40px rgba(45, 212, 191, .25);
  --hero-grad: radial-gradient(1200px 600px at 20% 0%, #0d3a5c 0%, #061a2b 60%);
  --rain: rgba(45, 212, 191, .4);
}

[data-theme="matrix"] {
  --bg: #050a06;
  --bg-alt: #080f09;
  --surface: #0c160e;
  --surface-2: #112015;
  --text: #dffce6;
  --muted: #7fb58c;
  --border: #1d3a24;
  --accent: #22c55e;
  --accent-2: #a3e635;
  --accent-text: #03140a;
  --ok: #4ade80;
  --shadow: 0 10px 30px rgba(0, 0, 0, .5);
  --shadow-hover: 0 18px 40px rgba(34, 197, 94, .25);
  --hero-grad: radial-gradient(1000px 500px at 80% 0%, #0d2614 0%, #050a06 60%);
  --rain: rgba(34, 197, 94, .55);
}

/* ---------- base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
  transition: background-color .4s var(--ease), color .4s var(--ease);
  -webkit-font-smoothing: antialiased;
}
img { display: block; max-width: 100%; }
[hidden] { display: none !important; }
a { color: var(--accent); text-decoration: none; }
h1, h2, h3 { margin: 0; line-height: 1.15; letter-spacing: -.01em; }
h2 { font-size: clamp(1.5rem, 2.4vw, 2rem); }
h3 { font-size: 1.1rem; }
p { margin: 0; }
.wrap { width: min(100% - 2.5rem, var(--maxw)); margin-inline: auto; }
.muted { color: var(--muted); }
.eyebrow {
  text-transform: uppercase; letter-spacing: .14em; font-size: .72rem; font-weight: 700;
  color: var(--accent); margin-bottom: .4rem;
}
.skip-link {
  position: absolute; left: -999px; top: 8px; background: var(--accent); color: var(--accent-text);
  padding: .5rem .8rem; border-radius: 8px; z-index: 100;
}
.skip-link:focus { left: 8px; }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--surface) 82%, transparent);
  backdrop-filter: blur(14px); -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
  transition: background-color .4s var(--ease);
}
.topbar-inner { display: flex; align-items: center; gap: 1.5rem; min-height: 68px; }
.brand { display: flex; align-items: center; gap: .8rem; color: var(--text); }
.brand-logo { height: 40px; width: auto; border-radius: 6px; background: #fff; padding: 3px; }
.brand-text { display: flex; flex-direction: column; line-height: 1.15; }
.brand-title { font-weight: 700; font-size: .98rem; }
.brand-sep { color: var(--accent); margin: 0 .2rem; }
.brand-sub { font-size: .78rem; color: var(--muted); }
.nav { display: flex; gap: .2rem; margin-left: auto; }
.nav a {
  color: var(--muted); font-weight: 600; font-size: .92rem; padding: .5rem .8rem; border-radius: 999px;
  transition: color .2s, background-color .2s;
}
.nav a:hover { color: var(--text); background: var(--surface-2); }

.theme-picker {
  display: flex; gap: .35rem; padding: .3rem; border-radius: 999px;
  background: var(--surface-2); border: 1px solid var(--border);
}
.theme-btn {
  width: 30px; height: 30px; border-radius: 50%; border: 2px solid transparent; background: none; padding: 0;
  cursor: pointer; display: grid; place-items: center; transition: transform .2s var(--ease), border-color .2s;
}
.theme-btn:hover { transform: scale(1.12); }
.theme-btn.active { border-color: var(--accent); }
.swatch { width: 18px; height: 18px; border-radius: 50%; display: block; box-shadow: inset 0 0 0 1px rgba(0,0,0,.12); }
.sw-light { background: linear-gradient(135deg, #ffffff 50%, #0ea5e9 50%); }
.sw-dark { background: linear-gradient(135deg, #182033 50%, #38bdf8 50%); }
.sw-ocean { background: linear-gradient(135deg, #0b2a44 50%, #2dd4bf 50%); }
.sw-matrix { background: linear-gradient(135deg, #0c160e 50%, #22c55e 50%); }

.menu-btn { display: none; }

/* ---------- buttons ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: .5rem;
  padding: .75rem 1.3rem; border-radius: 999px; font-weight: 700; font-size: .95rem;
  border: 1px solid transparent; cursor: pointer; font-family: inherit;
  transition: transform .2s var(--ease), box-shadow .2s var(--ease), background-color .2s, color .2s;
}
.btn:hover { transform: translateY(-2px); }
.btn:active { transform: translateY(0); }
.btn-primary { background: var(--accent); color: var(--accent-text); box-shadow: 0 8px 20px color-mix(in srgb, var(--accent) 35%, transparent); }
.btn-ghost { background: transparent; color: var(--text); border-color: var(--border); }
.btn-ghost:hover { background: var(--surface-2); }
.btn-small { padding: .5rem .95rem; font-size: .85rem; background: var(--surface-2); color: var(--text); border-color: var(--border); }

/* ---------- hero ---------- */
.hero { position: relative; overflow: hidden; background: var(--hero-grad); border-bottom: 1px solid var(--border); }
.hero-canvas { position: absolute; inset: 0; width: 100%; height: 100%; opacity: .9; pointer-events: none; }
.hero-inner {
  position: relative; display: grid; grid-template-columns: 1.3fr .9fr; gap: 2.5rem; align-items: center;
  padding: clamp(3rem, 7vw, 5.5rem) 0;
}
.hero-title { font-size: clamp(2.4rem, 5.5vw, 4rem); font-weight: 800; letter-spacing: -.03em; }
.accent { color: var(--accent); }
.hero-lead { margin: 1rem 0 1.6rem; font-size: 1.08rem; color: var(--muted); max-width: 52ch; }
.hero-actions { display: flex; gap: .7rem; flex-wrap: wrap; }

.notice {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 1.4rem 1.5rem; box-shadow: var(--shadow); position: relative; overflow: hidden;
}
.notice::before {
  content: ""; position: absolute; inset: 0 auto 0 0; width: 5px;
  background: linear-gradient(var(--accent), var(--accent-2));
}
.notice-head { display: flex; align-items: center; gap: .6rem; margin-bottom: .6rem; }
.notice-head h2 { font-size: 1.05rem; }
.pulse {
  width: 10px; height: 10px; border-radius: 50%; background: var(--accent-2);
  box-shadow: 0 0 0 0 color-mix(in srgb, var(--accent-2) 60%, transparent);
  animation: pulse 1.8s infinite;
}
@keyframes pulse {
  0% { box-shadow: 0 0 0 0 color-mix(in srgb, var(--accent-2) 60%, transparent); }
  70% { box-shadow: 0 0 0 10px transparent; }
  100% { box-shadow: 0 0 0 0 transparent; }
}
.notice-sprint {
  display: inline-block; font-family: var(--mono); font-size: .8rem; font-weight: 700;
  background: var(--surface-2); border: 1px solid var(--border); padding: .25rem .6rem; border-radius: 8px;
  margin-bottom: .7rem;
}
.notice-list { margin: 0; padding-left: 1.1rem; color: var(--muted); font-size: .95rem; }
.notice-list li + li { margin-top: .35rem; }

/* ---------- sections ---------- */
.section { padding: clamp(3rem, 6vw, 4.5rem) 0; }
.section-alt { background: var(--bg-alt); border-block: 1px solid var(--border); transition: background-color .4s var(--ease); }
.section-head {
  display: flex; justify-content: space-between; align-items: flex-end; gap: 1.5rem; flex-wrap: wrap;
  margin-bottom: 1.8rem;
}
.search {
  display: flex; align-items: center; gap: .55rem; background: var(--surface); border: 1px solid var(--border);
  border-radius: 999px; padding: .55rem 1rem; min-width: min(100%, 320px); box-shadow: var(--shadow);
  transition: box-shadow .2s, border-color .2s;
}
.search:focus-within { border-color: var(--accent); box-shadow: 0 0 0 4px color-mix(in srgb, var(--accent) 20%, transparent); }
.search svg { width: 18px; height: 18px; fill: none; stroke: var(--muted); stroke-width: 2; stroke-linecap: round; }
.search input { border: 0; background: transparent; color: var(--text); font: inherit; width: 100%; outline: none; }
.search input::placeholder { color: var(--muted); }
.empty { color: var(--muted); text-align: center; padding: 2rem 0; }

/* ---------- tiles ---------- */
.tile-group { margin-bottom: 2.2rem; }
.tile-group h3 {
  display: flex; align-items: center; gap: .7rem; margin-bottom: 1rem; font-size: .95rem;
  color: var(--muted); text-transform: uppercase; letter-spacing: .1em;
}
.tile-group h3::after { content: ""; flex: 1; height: 1px; background: var(--border); }
.tiles { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 1rem; }
.tile {
  position: relative; display: flex; flex-direction: column; gap: .55rem;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 1.15rem 1.2rem 1.1rem; color: var(--text); box-shadow: var(--shadow);
  transition: transform .3s var(--ease), box-shadow .3s var(--ease), border-color .3s;
  overflow: hidden;
}
.tile::after {
  content: ""; position: absolute; inset: auto 0 0 0; height: 3px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transform: scaleX(0); transform-origin: left; transition: transform .35s var(--ease);
}
.tile:hover { transform: translateY(-5px); box-shadow: var(--shadow-hover); border-color: color-mix(in srgb, var(--accent) 50%, var(--border)); }
.tile:hover::after { transform: scaleX(1); }
.tile-top { display: flex; align-items: center; justify-content: space-between; gap: .5rem; }
.tile-title { font-weight: 700; font-size: 1rem; line-height: 1.3; }
.tile-desc { color: var(--muted); font-size: .86rem; }
.tile-arrow { margin-left: auto; color: var(--accent); font-weight: 800; transition: transform .25s var(--ease); }
.tile:hover .tile-arrow { transform: translateX(4px); }

.badge {
  display: inline-flex; align-items: center; gap: .3rem; font-size: .68rem; font-weight: 800; letter-spacing: .06em;
  text-transform: uppercase; padding: .22rem .5rem; border-radius: 6px; white-space: nowrap;
  background: var(--surface-2); color: var(--muted); border: 1px solid var(--border);
}
.badge-pdf { color: #ef4444; border-color: color-mix(in srgb, #ef4444 35%, var(--border)); }
.badge-word { color: #2563eb; border-color: color-mix(in srgb, #2563eb 35%, var(--border)); }
.badge-ppt { color: #ea580c; border-color: color-mix(in srgb, #ea580c 35%, var(--border)); }
.badge-excel { color: #16a34a; border-color: color-mix(in srgb, #16a34a 35%, var(--border)); }
.badge-folder { color: #ca8a04; border-color: color-mix(in srgb, #ca8a04 35%, var(--border)); }
.badge-form { color: #7c3aed; border-color: color-mix(in srgb, #7c3aed 35%, var(--border)); }
.badge-web { color: var(--accent); border-color: color-mix(in srgb, var(--accent) 35%, var(--border)); }
[data-theme="dark"] .badge-pdf, [data-theme="ocean"] .badge-pdf, [data-theme="matrix"] .badge-pdf { color: #f87171; }
[data-theme="dark"] .badge-word, [data-theme="ocean"] .badge-word, [data-theme="matrix"] .badge-word { color: #60a5fa; }
[data-theme="dark"] .badge-ppt, [data-theme="ocean"] .badge-ppt, [data-theme="matrix"] .badge-ppt { color: #fb923c; }
[data-theme="dark"] .badge-excel, [data-theme="ocean"] .badge-excel, [data-theme="matrix"] .badge-excel { color: #4ade80; }
[data-theme="dark"] .badge-folder, [data-theme="ocean"] .badge-folder, [data-theme="matrix"] .badge-folder { color: #facc15; }
[data-theme="dark"] .badge-form, [data-theme="ocean"] .badge-form, [data-theme="matrix"] .badge-form { color: #a78bfa; }

/* ---------- progress ---------- */
.year-switch { display: inline-flex; background: var(--surface); border: 1px solid var(--border); border-radius: 999px; padding: .3rem; box-shadow: var(--shadow); }
.year-tab {
  border: 0; background: transparent; color: var(--muted); font: inherit; font-weight: 700; padding: .55rem 1.2rem;
  border-radius: 999px; cursor: pointer; transition: background-color .25s, color .25s;
}
.year-tab[aria-selected="true"] { background: var(--accent); color: var(--accent-text); }

.progress-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 1.4rem 1.5rem;
  box-shadow: var(--shadow); margin-bottom: 1.6rem;
}
.progress-top { display: flex; justify-content: space-between; align-items: center; gap: 1rem; margin-bottom: 1rem; }
.progress-label { font-weight: 800; font-size: 1.1rem; }
.progress-stat { color: var(--muted); font-size: .92rem; }
.ring {
  --p: 0; width: 76px; height: 76px; border-radius: 50%; display: grid; place-items: center; font-weight: 800; font-size: .92rem;
  background: conic-gradient(var(--accent) calc(var(--p) * 1%), var(--surface-2) 0);
  transition: --p .6s;
}
.ring span { width: 58px; height: 58px; border-radius: 50%; background: var(--surface); display: grid; place-items: center; }
.bar { height: 10px; background: var(--surface-2); border-radius: 999px; overflow: hidden; }
.bar-fill { height: 100%; width: 0; border-radius: 999px; background: linear-gradient(90deg, var(--accent), var(--accent-2)); transition: width .6s var(--ease); }
.progress-tools { display: flex; gap: .6rem; margin-top: 1rem; flex-wrap: wrap; }

.tracker { display: grid; gap: 1.2rem; }
.topic-block { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow); overflow: hidden; }
.topic-head {
  display: flex; align-items: center; gap: .8rem; padding: .9rem 1.2rem; background: var(--surface-2); border-bottom: 1px solid var(--border);
}
.topic-code { font-family: var(--mono); font-weight: 800; color: var(--accent); font-size: .95rem; }
.topic-name { font-weight: 700; }
.topic-count { margin-left: auto; font-size: .8rem; color: var(--muted); font-weight: 700; }
.item-list { list-style: none; margin: 0; padding: 0; }
.item {
  display: grid; grid-template-columns: auto 1fr auto; align-items: center; gap: .9rem; padding: .8rem 1.2rem;
  border-bottom: 1px solid var(--border); transition: background-color .25s;
}
.item:last-child { border-bottom: 0; }
.item:hover { background: color-mix(in srgb, var(--surface-2) 60%, transparent); }
.item.done .item-title { color: var(--muted); text-decoration: line-through; text-decoration-color: color-mix(in srgb, var(--ok) 60%, transparent); }
.check { position: relative; width: 24px; height: 24px; display: block; cursor: pointer; }
.check input { position: absolute; inset: 0; opacity: 0; margin: 0; cursor: pointer; width: 100%; height: 100%; }
.check span {
  position: absolute; inset: 0; border-radius: 7px; border: 2px solid var(--border); background: var(--surface);
  transition: background-color .2s, border-color .2s, transform .2s var(--ease);
}
.check span::after {
  content: ""; position: absolute; left: 7px; top: 3px; width: 6px; height: 11px;
  border: solid var(--accent-text); border-width: 0 3px 3px 0; transform: rotate(45deg) scale(0); transition: transform .2s var(--ease);
}
.check input:checked + span { background: var(--ok); border-color: var(--ok); transform: scale(1.05); }
.check input:checked + span::after { transform: rotate(45deg) scale(1); }
.check input:focus-visible + span { outline: 3px solid var(--accent); outline-offset: 2px; }
.item-main { min-width: 0; }
.item-title { font-weight: 600; display: block; }
.item-sub { font-size: .8rem; color: var(--muted); }
.item-actions { display: flex; gap: .4rem; align-items: center; flex-wrap: wrap; justify-content: flex-end; }
.open-link {
  display: inline-flex; align-items: center; gap: .35rem; padding: .4rem .7rem; border-radius: 8px; font-size: .8rem; font-weight: 700;
  border: 1px solid var(--border); color: var(--text); background: var(--surface); transition: border-color .2s, transform .2s var(--ease), background-color .2s;
}
.open-link:hover { border-color: var(--accent); transform: translateY(-1px); background: var(--surface-2); }
.open-link.disabled { opacity: .55; pointer-events: none; }

/* ---------- quizzes ---------- */
.how-to {
  background: var(--surface); border: 1px dashed color-mix(in srgb, var(--accent) 55%, var(--border)); border-radius: var(--radius);
  padding: 1.2rem 1.4rem; margin-bottom: 1.8rem; max-width: 640px;
}
.how-to h3 { margin-bottom: .5rem; }
.how-to ol { margin: 0; padding-left: 1.2rem; color: var(--muted); }
.how-to li + li { margin-top: .25rem; }
.quiz-cols { display: grid; grid-template-columns: 1fr 1fr; gap: 1.6rem; }
.quiz-col h3 { display: flex; align-items: center; gap: .55rem; margin-bottom: .9rem; }
.dot { width: 12px; height: 12px; border-radius: 50%; display: inline-block; }
.dot-c1 { background: #22c55e; }
.dot-c2 { background: #facc15; }
.quiz-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: .7rem; }
.quiz {
  position: relative; display: flex; flex-direction: column; gap: .2rem; padding: .85rem .95rem; border-radius: var(--radius-sm);
  background: var(--surface); border: 1px solid var(--border); color: var(--text); box-shadow: var(--shadow);
  transition: transform .25s var(--ease), box-shadow .25s var(--ease), border-color .25s;
}
.quiz::before { content: ""; position: absolute; left: 0; top: 10px; bottom: 10px; width: 4px; border-radius: 0 4px 4px 0; }
.quiz.c1::before { background: #22c55e; }
.quiz.c2::before { background: #facc15; }
.quiz:hover { transform: translateY(-4px); box-shadow: var(--shadow-hover); border-color: color-mix(in srgb, var(--accent) 50%, var(--border)); }
.quiz-code { font-family: var(--mono); font-weight: 800; font-size: .95rem; }
.quiz-name { font-size: .78rem; color: var(--muted); }

/* ---------- footer ---------- */
.footer { border-top: 1px solid var(--border); padding: 1.8rem 0; color: var(--muted); font-size: .9rem; }
.footer-inner { display: flex; justify-content: space-between; gap: 1rem; flex-wrap: wrap; align-items: center; }
.to-top { font-weight: 700; }

/* ---------- toast ---------- */
.toast {
  position: fixed; left: 50%; bottom: 1.4rem; transform: translate(-50%, 20px); opacity: 0; pointer-events: none;
  background: var(--text); color: var(--bg); padding: .65rem 1.1rem; border-radius: 999px; font-weight: 600; font-size: .9rem;
  transition: opacity .3s, transform .3s var(--ease); z-index: 60; box-shadow: var(--shadow);
}
.toast.show { opacity: 1; transform: translate(-50%, 0); }

/* ---------- reveal animation ---------- */
.reveal { opacity: 0; transform: translateY(18px); transition: opacity .7s var(--ease), transform .7s var(--ease); }
.reveal.in { opacity: 1; transform: none; }
.tile, .quiz, .topic-block { animation: popIn .5s var(--ease) both; }
@keyframes popIn { from { opacity: 0; transform: translateY(12px) scale(.98); } to { opacity: 1; transform: none; } }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
  .reveal { opacity: 1; transform: none; }
  html { scroll-behavior: auto; }
}

/* ---------- responsive ---------- */
@media (max-width: 900px) {
  .hero-inner { grid-template-columns: 1fr; }
  .quiz-cols { grid-template-columns: 1fr; }
}
@media (max-width: 720px) {
  .topbar-inner { flex-wrap: wrap; gap: .8rem; padding: .6rem 0; }
  .brand-title { font-size: .9rem; }
  .nav { display: none; width: 100%; flex-direction: column; order: 5; }
  .nav.open { display: flex; }
  .theme-picker { margin-left: auto; }
  .menu-btn {
    display: inline-flex; flex-direction: column; gap: 4px; justify-content: center; width: 40px; height: 40px;
    border: 1px solid var(--border); background: var(--surface); border-radius: 10px; cursor: pointer;
  }
  .menu-btn span { width: 18px; height: 2px; background: var(--text); margin-inline: auto; border-radius: 2px; }
  .item { grid-template-columns: auto 1fr; }
  .item-actions { grid-column: 2; justify-content: flex-start; }
}