/* =============================================================================
   Qiki design system
   - Tokens (CSS custom properties) are the single source of truth. Tailwind's @theme
     (app/views/partials/head.php) maps utilities such as bg-brand-600 onto these tokens.
   - Component classes live in @layer components so Tailwind utilities can override them.
   - Works without Tailwind too: if the CDN fails, components remain readable and usable.
   ============================================================================= */

@layer theme, base, components, utilities;

@font-face {
  font-family: "Plus Jakarta Sans";
  src: url("../fonts/plus-jakarta-sans-var.woff2") format("woff2");
  font-weight: 200 800;
  font-style: normal;
  font-display: swap;
}
@font-face {
  font-family: "Bricolage Grotesque";
  src: url("../fonts/bricolage-grotesque-var.woff2") format("woff2");
  font-weight: 200 800;
  font-style: normal;
  font-display: swap;
}

:root {
  /* Neutrals: warm paper + deep ink */
  --qk-ink-950: #0f1024;
  --qk-ink-900: #17182e;
  --qk-ink-800: #26283f;
  --qk-ink-700: #3b3d57;
  --qk-ink-600: #50536e;
  --qk-ink-500: #5f627c; /* minimum for body-size muted text on paper (≥ 5:1) */
  --qk-ink-400: #8b8da3;
  --qk-ink-300: #b9bacb;
  --qk-paper: #faf7f1;
  --qk-paper-deep: #f3eee4;
  --qk-surface: #ffffff;
  --qk-line: #e7e0d3;
  --qk-line-strong: #d6cdbd;

  /* Brand: pine/teal, calm, trustworthy */
  --qk-brand-50: #edf9f5;
  --qk-brand-100: #d3f1e6;
  --qk-brand-200: #a9e2cf;
  --qk-brand-300: #72cbb0;
  --qk-brand-400: #39ad8f;
  --qk-brand-500: #169276;
  --qk-brand-600: #0c7862;
  --qk-brand-700: #0b6052;
  --qk-brand-800: #0d4d43;
  --qk-brand-900: #0c3f38;

  /* Accent: marigold, warmth, highlights, "spark" moments */
  --qk-sun-50: #fff8e6;
  --qk-sun-100: #ffefc2;
  --qk-sun-200: #ffdf85;
  --qk-sun-300: #ffcd4d;
  --qk-sun-400: #fbb92a;
  --qk-sun-500: #ef9f0c;
  --qk-sun-700: #9a5a00;

  /* Accent: coral, secondary energy, used sparingly */
  --qk-coral-50: #fff1ed;
  --qk-coral-100: #ffe0d7;
  --qk-coral-400: #f88a6e;
  --qk-coral-500: #ee6a4d;
  --qk-coral-700: #b23f28;

  /* Subject accents */
  --qk-subject-indigo: #5457d6;
  --qk-subject-sky: #2b86cf;
  --qk-subject-coral: #e0573a;
  --qk-subject-leaf: #2f8f45;
  --qk-subject-plum: #9446c4;
  --qk-subject-amber: #c27a00;
  --qk-subject-teal: #0c7862;

  /* Semantic states (always paired with an icon or text, never colour alone) */
  --qk-success: #12775a;
  --qk-success-bg: #e6f6ef;
  --qk-warning: #8f5300;
  --qk-warning-bg: #fff4dc;
  --qk-error: #b3261e;
  --qk-error-bg: #fdecea;
  --qk-info: #2361b8;
  --qk-info-bg: #e8f0fc;
  --qk-locked: #6c6f86;
  --qk-locked-bg: #eeeef3;

  /* Shape */
  --qk-radius-xs: 6px;
  --qk-radius-sm: 10px;
  --qk-radius-md: 14px;
  --qk-radius-lg: 20px;
  --qk-radius-xl: 28px;
  --qk-radius-pill: 999px;

  /* Elevation */
  --qk-shadow-xs: 0 1px 2px rgb(23 24 46 / 0.06);
  --qk-shadow-sm: 0 1px 2px rgb(23 24 46 / 0.06), 0 2px 6px -2px rgb(23 24 46 / 0.08);
  --qk-shadow-md: 0 2px 4px rgb(23 24 46 / 0.04), 0 12px 28px -12px rgb(23 24 46 / 0.22);
  --qk-shadow-lg: 0 4px 8px rgb(23 24 46 / 0.04), 0 28px 56px -24px rgb(23 24 46 / 0.32);
  --qk-ring: 0 0 0 3px var(--qk-surface), 0 0 0 5px var(--qk-brand-500);

  /* Type */
  --qk-font-sans: "Plus Jakarta Sans", ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans", sans-serif;
  --qk-font-display: "Bricolage Grotesque", "Plus Jakarta Sans", ui-sans-serif, system-ui, sans-serif;
  --qk-font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  /* Motion */
  --qk-ease: cubic-bezier(0.2, 0.7, 0.2, 1);
  --qk-fast: 140ms;
  --qk-base: 220ms;

  /* Layout */
  --qk-header-h: 4rem;
  --qk-container: 76rem;
}

/* ----------------------------------------------------------------------------- Base */
@layer base {
  *, *::before, *::after { box-sizing: border-box; }
  html {
    -webkit-text-size-adjust: 100%;
    text-size-adjust: 100%;
    scroll-padding-top: calc(var(--qk-header-h) + 1rem);
  }
  body {
    margin: 0;
    min-height: 100dvh;
    display: flex;
    flex-direction: column;
    background: var(--qk-paper);
    color: var(--qk-ink-900);
    font-family: var(--qk-font-sans);
    font-size: 1rem;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    text-rendering: optimizeLegibility;
    overflow-x: hidden;
  }
  main { flex: 1 0 auto; }
  /* `html …` adds one type selector of specificity so these win over Tailwind's preflight
     (same layer, injected later) while utilities (a later layer) can still override them. */
  html :is(h1, h2, h3, h4) {
    font-family: var(--qk-font-display);
    color: var(--qk-ink-950);
    line-height: 1.15;
    letter-spacing: -0.015em;
    font-weight: 700;
    margin: 0;
    text-wrap: balance;
  }
  p { margin: 0; text-wrap: pretty; }
  html a { color: var(--qk-brand-700); text-decoration: underline; text-underline-offset: 0.18em; }
  img, svg { max-width: 100%; }
  img { height: auto; }
  ::selection { background: var(--qk-sun-200); color: var(--qk-ink-950); }

  :focus { outline: none; }
  :focus-visible {
    outline: 3px solid var(--qk-brand-500);
    outline-offset: 2px;
    border-radius: var(--qk-radius-xs);
  }

  .icon { display: inline-block; flex: none; fill: none; stroke: currentColor; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; vertical-align: middle; }
  .size-4 { width: 1rem; height: 1rem; }
  .size-5 { width: 1.25rem; height: 1.25rem; }
  .size-6 { width: 1.5rem; height: 1.5rem; }

  [hidden] { display: none !important; }
  [x-cloak] { visibility: hidden; }
}

/* ----------------------------------------------------------------------------- Components */
@layer components {
  .container-qk { width: 100%; max-width: var(--qk-container); margin-inline: auto; padding-inline: 1rem; }
  @media (min-width: 640px) { .container-qk { padding-inline: 1.5rem; } }
  @media (min-width: 1024px) { .container-qk { padding-inline: 2rem; } }

  .sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0; }
  .skip-link {
    position: absolute; left: 1rem; top: -4rem; z-index: 100;
    background: var(--qk-ink-900); color: #fff; padding: 0.6rem 1rem; border-radius: var(--qk-radius-sm);
    font-weight: 600; text-decoration: none; transition: top var(--qk-fast) var(--qk-ease);
  }
  .skip-link:focus { top: 0.75rem; }

  .eyebrow {
    display: inline-flex; align-items: center; gap: 0.5rem;
    font-size: 0.8125rem; font-weight: 700; letter-spacing: 0.08em; text-transform: uppercase;
    color: var(--qk-brand-700);
  }
  .text-muted { color: var(--qk-ink-500); }

  /* Buttons ------------------------------------------------------------------ */
  .btn {
    --btn-bg: var(--qk-surface);
    --btn-fg: var(--qk-ink-900);
    --btn-border: var(--qk-line-strong);
    --btn-edge: var(--qk-line-strong);
    position: relative;
    display: inline-flex; align-items: center; justify-content: center; gap: 0.5rem;
    min-height: 2.75rem; padding: 0.625rem 1.125rem;
    border: 1.5px solid var(--btn-border); border-radius: var(--qk-radius-md);
    background: var(--btn-bg); color: var(--btn-fg);
    box-shadow: 0 2px 0 var(--btn-edge);
    font: inherit; font-weight: 700; font-size: 0.9375rem; line-height: 1.2; letter-spacing: 0.005em;
    text-decoration: none; white-space: nowrap; cursor: pointer; user-select: none;
    transition: transform var(--qk-fast) var(--qk-ease), box-shadow var(--qk-fast) var(--qk-ease), background-color var(--qk-fast) var(--qk-ease), border-color var(--qk-fast) var(--qk-ease);
    -webkit-tap-highlight-color: transparent;
  }
  .btn:hover { transform: translateY(-1px); box-shadow: 0 3px 0 var(--btn-edge); }
  .btn:active { transform: translateY(2px); box-shadow: 0 0 0 var(--btn-edge); }
  .btn:focus-visible { outline: 3px solid var(--qk-brand-500); outline-offset: 3px; }
  .btn[disabled], .btn[aria-disabled="true"] { cursor: not-allowed; opacity: 0.55; transform: none; box-shadow: 0 2px 0 var(--btn-edge); }
  .btn .icon { width: 1.125rem; height: 1.125rem; }

  .btn-primary { --btn-bg: var(--qk-brand-600); --btn-fg: #fff; --btn-border: var(--qk-brand-700); --btn-edge: var(--qk-brand-800); }
  .btn-primary:hover { --btn-bg: var(--qk-brand-500); }
  .btn-accent { --btn-bg: var(--qk-sun-400); --btn-fg: var(--qk-ink-950); --btn-border: var(--qk-sun-500); --btn-edge: var(--qk-sun-700); }
  .btn-accent:hover { --btn-bg: var(--qk-sun-300); }
  .btn-secondary { --btn-bg: var(--qk-surface); --btn-fg: var(--qk-ink-900); }
  .btn-secondary:hover { --btn-bg: var(--qk-paper); }
  .btn-tertiary {
    --btn-bg: transparent; --btn-border: transparent; --btn-edge: transparent; --btn-fg: var(--qk-brand-700);
    box-shadow: none; padding-inline: 0.75rem;
  }
  .btn-tertiary:hover { --btn-bg: var(--qk-brand-50); box-shadow: none; transform: none; }
  .btn-tertiary:active { transform: none; }
  .btn-danger { --btn-bg: var(--qk-error); --btn-fg: #fff; --btn-border: #8e1d17; --btn-edge: #6f1712; }
  .btn-sm { min-height: 2.25rem; padding: 0.4rem 0.8rem; font-size: 0.875rem; border-radius: var(--qk-radius-sm); }
  .btn-lg { min-height: 3.25rem; padding: 0.8rem 1.5rem; font-size: 1.0625rem; border-radius: var(--qk-radius-lg); }
  .btn-block { width: 100%; }
  .btn-icon { padding: 0; width: 2.75rem; min-width: 2.75rem; }

  /* Loading state: set aria-busy="true" on the button (see ui.js setBusy) */
  .btn[aria-busy="true"] { color: transparent !important; pointer-events: none; }
  .btn[aria-busy="true"]::after {
    content: ""; position: absolute; width: 1.15rem; height: 1.15rem; inset: 0; margin: auto;
    border-radius: 50%; border: 2.5px solid var(--btn-fg); border-right-color: transparent;
    animation: qk-spin 0.7s linear infinite;
  }

  /* Forms -------------------------------------------------------------------- */
  .field { display: grid; gap: 0.375rem; }
  .label { font-weight: 700; font-size: 0.9375rem; color: var(--qk-ink-900); }
  .label-optional { font-weight: 500; color: var(--qk-ink-500); font-size: 0.8125rem; margin-left: 0.25rem; }
  .hint { font-size: 0.8125rem; color: var(--qk-ink-500); line-height: 1.45; }
  .input, .select, .textarea {
    width: 100%; min-height: 2.875rem; padding: 0.625rem 0.875rem;
    border: 1.5px solid var(--qk-line-strong); border-radius: var(--qk-radius-md);
    background: var(--qk-surface); color: var(--qk-ink-900);
    font: inherit; font-size: 1rem; line-height: 1.4;
    transition: border-color var(--qk-fast) var(--qk-ease), box-shadow var(--qk-fast) var(--qk-ease);
  }
  .input::placeholder, .textarea::placeholder { color: var(--qk-ink-400); }
  .input:hover, .select:hover, .textarea:hover { border-color: var(--qk-ink-400); }
  .input:focus-visible, .select:focus-visible, .textarea:focus-visible {
    outline: none; border-color: var(--qk-brand-500); box-shadow: 0 0 0 4px rgb(22 146 118 / 0.18);
  }
  .select {
    appearance: none; padding-right: 2.5rem; cursor: pointer;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%233b3d57' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E");
    background-repeat: no-repeat; background-position: right 0.85rem center; background-size: 1.1rem;
  }
  .input[aria-invalid="true"], .select[aria-invalid="true"], .textarea[aria-invalid="true"] { border-color: var(--qk-error); }
  .input[aria-invalid="true"]:focus-visible { box-shadow: 0 0 0 4px rgb(179 38 30 / 0.16); }
  .field-error {
    display: flex; align-items: flex-start; gap: 0.375rem;
    color: var(--qk-error); font-size: 0.875rem; font-weight: 600; line-height: 1.4;
  }
  .field-error .icon { width: 1rem; height: 1rem; margin-top: 0.1rem; }
  .input-group { position: relative; }
  .input-group .input { padding-right: 3rem; }
  .input-group .input-action {
    position: absolute; right: 0.25rem; top: 50%; transform: translateY(-50%);
    display: grid; place-items: center; width: 2.5rem; height: 2.5rem;
    border: 0; background: transparent; color: var(--qk-ink-500); border-radius: var(--qk-radius-sm); cursor: pointer;
  }
  .input-group .input-action:hover { color: var(--qk-ink-900); background: var(--qk-paper); }

  .check { display: flex; align-items: flex-start; gap: 0.75rem; cursor: pointer; font-size: 0.9375rem; line-height: 1.5; }
  .check input {
    appearance: none; flex: none; margin: 0.15rem 0 0; width: 1.25rem; height: 1.25rem;
    border: 2px solid var(--qk-ink-400); border-radius: 6px; background: var(--qk-surface); cursor: pointer;
    display: grid; place-items: center; transition: background-color var(--qk-fast), border-color var(--qk-fast);
  }
  .check input[type="radio"] { border-radius: 50%; }
  .check input::after { content: ""; width: 0.6rem; height: 0.35rem; border: 2.5px solid #fff; border-top: 0; border-right: 0; transform: rotate(-45deg) translate(1px, -1px) scale(0); transition: transform var(--qk-fast) var(--qk-ease); }
  .check input[type="radio"]::after { width: 0.5rem; height: 0.5rem; border: 0; border-radius: 50%; background: #fff; transform: scale(0); }
  .check input:checked { background: var(--qk-brand-600); border-color: var(--qk-brand-600); }
  .check input:checked::after { transform: rotate(-45deg) translate(1px, -1px) scale(1); }
  .check input[type="radio"]:checked::after { transform: scale(1); }
  .check input:focus-visible { outline: 3px solid var(--qk-brand-500); outline-offset: 2px; }
  .check input[aria-invalid="true"] { border-color: var(--qk-error); }

  /* Radio/choice cards (account type, quiz answers) */
  .choice { position: relative; display: block; cursor: pointer; }
  .choice input { position: absolute; opacity: 0; inset: 0; cursor: pointer; }
  .choice-body {
    display: flex; align-items: center; gap: 0.875rem; height: 100%;
    padding: 0.875rem 1rem; border: 1.5px solid var(--qk-line-strong); border-radius: var(--qk-radius-md);
    background: var(--qk-surface); box-shadow: 0 2px 0 var(--qk-line);
    transition: border-color var(--qk-fast), background-color var(--qk-fast), box-shadow var(--qk-fast);
  }
  .choice:hover .choice-body { border-color: var(--qk-ink-400); }
  .choice input:checked + .choice-body { border-color: var(--qk-brand-600); background: var(--qk-brand-50); box-shadow: 0 2px 0 var(--qk-brand-600); }
  .choice input:focus-visible + .choice-body { outline: 3px solid var(--qk-brand-500); outline-offset: 2px; }
  .choice-mark {
    flex: none; display: grid; place-items: center; width: 1.25rem; height: 1.25rem; border-radius: 50%;
    border: 2px solid var(--qk-ink-400); background: var(--qk-surface);
  }
  .choice input:checked + .choice-body .choice-mark { border-color: var(--qk-brand-600); background: radial-gradient(circle, var(--qk-brand-600) 0 45%, transparent 50%); }

  /* Alerts / inline feedback ------------------------------------------------- */
  .alert {
    display: flex; gap: 0.75rem; align-items: flex-start;
    padding: 0.875rem 1rem; border-radius: var(--qk-radius-md); border: 1.5px solid transparent;
    font-size: 0.9375rem; line-height: 1.5;
  }
  .alert .icon { width: 1.25rem; height: 1.25rem; margin-top: 0.1rem; }
  .alert-title { font-weight: 700; }
  .alert-error { background: var(--qk-error-bg); color: #7a1a14; border-color: #f4c7c2; }
  .alert-error .icon { color: var(--qk-error); }
  .alert-success { background: var(--qk-success-bg); color: #0b4f3c; border-color: #b9e5d3; }
  .alert-success .icon { color: var(--qk-success); }
  .alert-warning { background: var(--qk-warning-bg); color: #6b3e00; border-color: #f6dca4; }
  .alert-warning .icon { color: var(--qk-warning); }
  .alert-info { background: var(--qk-info-bg); color: #193f78; border-color: #c8d9f5; }
  .alert-info .icon { color: var(--qk-info); }

  /* Cards --------------------------------------------------------------------- */
  .card {
    background: var(--qk-surface); border: 1px solid var(--qk-line); border-radius: var(--qk-radius-lg);
    box-shadow: var(--qk-shadow-sm);
  }
  .card-pad { padding: 1.25rem; }
  @media (min-width: 640px) { .card-pad { padding: 1.75rem; } }
  .card-link { display: block; color: inherit; text-decoration: none; transition: transform var(--qk-base) var(--qk-ease), box-shadow var(--qk-base) var(--qk-ease), border-color var(--qk-base); }
  .card-link:hover { transform: translateY(-3px); box-shadow: var(--qk-shadow-md); border-color: var(--qk-line-strong); }
  .card-link:focus-visible { outline: 3px solid var(--qk-brand-500); outline-offset: 3px; border-radius: var(--qk-radius-lg); }

  /* Course card */
  .course-card { display: flex; flex-direction: column; height: 100%; overflow: hidden; }
  .course-card-art {
    position: relative; aspect-ratio: 16 / 7; overflow: hidden;
    background: color-mix(in srgb, var(--accent, var(--qk-brand-600)) 14%, var(--qk-surface));
    border-bottom: 1px solid var(--qk-line);
  }
  .course-card-art::before, .course-card-art::after { content: ""; position: absolute; border-radius: 50%; }
  .course-card-art::before { width: 9rem; height: 9rem; right: -2rem; top: -3.5rem; background: color-mix(in srgb, var(--accent, var(--qk-brand-600)) 22%, transparent); }
  .course-card-art::after { width: 4.5rem; height: 4.5rem; right: 5.5rem; bottom: -2rem; background: color-mix(in srgb, var(--qk-sun-300) 55%, transparent); }
  .course-card-art .subject-glyph {
    position: absolute; left: 1.25rem; bottom: 1rem; z-index: 1;
    display: grid; place-items: center; width: 3rem; height: 3rem; border-radius: var(--qk-radius-md);
    background: var(--qk-surface); color: var(--accent, var(--qk-brand-600)); box-shadow: var(--qk-shadow-sm);
  }
  .course-card-body { display: flex; flex-direction: column; gap: 0.75rem; padding: 1.125rem 1.25rem 1.25rem; flex: 1; }
  .course-card-title { font-size: 1.1875rem; line-height: 1.25; }
  .course-card-meta { display: flex; flex-wrap: wrap; gap: 0.375rem 1rem; color: var(--qk-ink-500); font-size: 0.8125rem; font-weight: 600; margin-top: auto; }
  .course-card-meta span { display: inline-flex; align-items: center; gap: 0.35rem; }

  /* Subject accent hooks: set --accent on any element */
  .accent-indigo { --accent: var(--qk-subject-indigo); }
  .accent-sky { --accent: var(--qk-subject-sky); }
  .accent-coral { --accent: var(--qk-subject-coral); }
  .accent-leaf { --accent: var(--qk-subject-leaf); }
  .accent-plum { --accent: var(--qk-subject-plum); }
  .accent-amber { --accent: var(--qk-subject-amber); }
  .accent-teal, .accent-brand { --accent: var(--qk-subject-teal); }

  /* Badges -------------------------------------------------------------------- */
  .badge {
    display: inline-flex; align-items: center; gap: 0.3rem;
    padding: 0.2rem 0.6rem; border-radius: var(--qk-radius-pill);
    font-size: 0.75rem; font-weight: 700; line-height: 1.4; letter-spacing: 0.01em; white-space: nowrap;
    background: var(--qk-paper-deep); color: var(--qk-ink-700); border: 1px solid transparent;
  }
  .badge .icon { width: 0.875rem; height: 0.875rem; stroke-width: 2.5; }
  .badge-brand { background: var(--qk-brand-50); color: var(--qk-brand-800); border-color: var(--qk-brand-100); }
  .badge-sun { background: var(--qk-sun-100); color: #6e4100; border-color: var(--qk-sun-200); }
  .badge-success { background: var(--qk-success-bg); color: var(--qk-success); border-color: #c4ead9; }
  .badge-warning { background: var(--qk-warning-bg); color: var(--qk-warning); border-color: #f6dca4; }
  .badge-error { background: var(--qk-error-bg); color: var(--qk-error); border-color: #f4c7c2; }
  .badge-info { background: var(--qk-info-bg); color: var(--qk-info); border-color: #c8d9f5; }
  .badge-locked { background: var(--qk-locked-bg); color: var(--qk-locked); border-color: #dcdce6; }
  .badge-accent { background: color-mix(in srgb, var(--accent) 12%, var(--qk-surface)); color: color-mix(in srgb, var(--accent) 80%, var(--qk-ink-950)); border-color: color-mix(in srgb, var(--accent) 22%, var(--qk-surface)); }

  /* Filter chips -------------------------------------------------------------- */
  .chip {
    display: inline-flex; align-items: center; gap: 0.45rem; min-height: 2.5rem; padding: 0.4rem 0.9rem;
    border-radius: var(--qk-radius-pill); border: 1.5px solid var(--qk-line-strong); background: var(--qk-surface);
    color: var(--qk-ink-800); font: inherit; font-size: 0.9rem; font-weight: 600; cursor: pointer; text-decoration: none; white-space: nowrap;
    transition: background-color var(--qk-fast), border-color var(--qk-fast), color var(--qk-fast);
  }
  .chip:hover { border-color: var(--qk-ink-400); }
  .chip[aria-pressed="true"], .chip[aria-current="true"] { background: var(--qk-ink-900); border-color: var(--qk-ink-900); color: #fff; }
  .chip .icon { width: 1rem; height: 1rem; }

  /* Header / navigation ------------------------------------------------------- */
  .site-header {
    position: sticky; top: 0; z-index: 40; height: var(--qk-header-h);
    background: color-mix(in srgb, var(--qk-paper) 88%, 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(--qk-base), box-shadow var(--qk-base);
  }
  .site-header[data-scrolled="true"] { border-bottom-color: var(--qk-line); box-shadow: 0 6px 20px -16px rgb(23 24 46 / 0.4); }
  .brand { display: inline-flex; align-items: center; gap: 0.55rem; text-decoration: none; color: var(--qk-ink-950); font-family: var(--qk-font-display); font-weight: 800; font-size: 1.5rem; letter-spacing: -0.03em; }
  .brand svg { width: 2.1rem; height: 2.1rem; }
  .nav-link {
    display: inline-flex; align-items: center; gap: 0.4rem; min-height: 2.5rem; padding: 0.4rem 0.8rem; border-radius: var(--qk-radius-sm);
    color: var(--qk-ink-700); font-weight: 600; font-size: 0.9375rem; text-decoration: none; transition: background-color var(--qk-fast), color var(--qk-fast);
  }
  .nav-link:hover { background: var(--qk-paper-deep); color: var(--qk-ink-950); }
  .nav-link[aria-current="page"] { color: var(--qk-brand-700); background: var(--qk-brand-50); }

  .drawer-backdrop { position: fixed; inset: 0; z-index: 60; background: rgb(15 16 36 / 0.45); opacity: 0; transition: opacity var(--qk-base) var(--qk-ease); }
  .drawer {
    position: fixed; inset: 0 0 0 auto; z-index: 61; width: min(22rem, 88vw); display: flex; flex-direction: column;
    background: var(--qk-surface); box-shadow: var(--qk-shadow-lg); transform: translateX(100%);
    transition: transform var(--qk-base) var(--qk-ease); overflow-y: auto; overscroll-behavior: contain;
  }
  .drawer[data-open="true"] { transform: none; }
  .drawer-backdrop[data-open="true"] { opacity: 1; }
  .drawer .nav-link { width: 100%; min-height: 3rem; font-size: 1rem; }

  .user-menu { position: relative; }
  .user-menu-panel {
    position: absolute; right: 0; top: calc(100% + 0.5rem); min-width: 15rem; z-index: 50; padding: 0.5rem;
    background: var(--qk-surface); border: 1px solid var(--qk-line); border-radius: var(--qk-radius-md); box-shadow: var(--qk-shadow-lg);
  }
  .menu-item {
    display: flex; align-items: center; gap: 0.6rem; width: 100%; min-height: 2.5rem; padding: 0.5rem 0.75rem; border: 0; border-radius: var(--qk-radius-sm);
    background: transparent; color: var(--qk-ink-800); font: inherit; font-size: 0.9375rem; font-weight: 600; text-align: left; text-decoration: none; cursor: pointer;
  }
  .menu-item:hover, .menu-item:focus-visible { background: var(--qk-paper); color: var(--qk-ink-950); }
  .avatar {
    display: grid; place-items: center; width: 2.25rem; height: 2.25rem; border-radius: 50%; flex: none;
    background: var(--qk-sun-200); color: var(--qk-ink-950); font-weight: 800; font-size: 0.875rem; font-family: var(--qk-font-display);
  }

  /* Footer -------------------------------------------------------------------- */
  .site-footer { margin-top: 5rem; background: var(--qk-ink-900); color: #d9dae6; }
  .site-footer a { color: #fff; text-decoration: none; }
  .site-footer a:hover { text-decoration: underline; }

  /* Feedback states ----------------------------------------------------------- */
  .empty-state {
    display: grid; justify-items: center; gap: 0.75rem; text-align: center;
    padding: 2.5rem 1.25rem; border: 1.5px dashed var(--qk-line-strong); border-radius: var(--qk-radius-lg); background: color-mix(in srgb, var(--qk-surface) 60%, transparent);
  }
  .empty-state-icon { display: grid; place-items: center; width: 3.5rem; height: 3.5rem; border-radius: 50%; background: var(--qk-sun-100); color: var(--qk-sun-700); }
  .empty-state-icon .icon { width: 1.6rem; height: 1.6rem; }
  .empty-state h3 { font-size: 1.1875rem; }
  .empty-state p { max-width: 34rem; color: var(--qk-ink-500); }

  .skeleton {
    position: relative; overflow: hidden; background: var(--qk-paper-deep); border-radius: var(--qk-radius-sm);
  }
  .skeleton::after {
    content: ""; position: absolute; inset: 0; transform: translateX(-100%);
    background: linear-gradient(90deg, transparent, rgb(255 255 255 / 0.65), transparent);
    animation: qk-shimmer 1.3s infinite;
  }

  .spinner { width: 1.5rem; height: 1.5rem; border-radius: 50%; border: 3px solid var(--qk-brand-100); border-top-color: var(--qk-brand-600); animation: qk-spin 0.8s linear infinite; }

  /* Toasts -------------------------------------------------------------------- */
  .toast-region {
    position: fixed; z-index: 80; left: 50%; bottom: max(1rem, env(safe-area-inset-bottom)); transform: translateX(-50%);
    display: grid; gap: 0.5rem; width: min(26rem, calc(100vw - 2rem)); pointer-events: none;
  }
  .toast {
    pointer-events: auto; display: flex; align-items: flex-start; gap: 0.75rem; padding: 0.875rem 1rem;
    border-radius: var(--qk-radius-md); background: var(--qk-ink-900); color: #fff; box-shadow: var(--qk-shadow-lg);
    font-size: 0.9375rem; font-weight: 600; line-height: 1.45; animation: qk-rise var(--qk-base) var(--qk-ease);
  }
  .toast .icon { width: 1.25rem; height: 1.25rem; margin-top: 0.05rem; }
  .toast-success .icon { color: var(--qk-brand-300); }
  .toast-error .icon { color: #ff9c8f; }
  .toast-info .icon { color: var(--qk-sun-300); }
  .toast-close { margin-left: auto; border: 0; background: transparent; color: #c7c8d6; cursor: pointer; padding: 0.1rem; border-radius: 6px; }
  .toast-close:hover { color: #fff; }

  /* Dialog -------------------------------------------------------------------- */
  .dialog {
    width: min(28rem, calc(100vw - 2rem)); margin: auto; padding: 0; border: 0; border-radius: var(--qk-radius-lg);
    background: var(--qk-surface); color: var(--qk-ink-900); box-shadow: var(--qk-shadow-lg);
  }
  .dialog::backdrop { background: rgb(15 16 36 / 0.5); }
  .dialog[open] { animation: qk-pop var(--qk-base) var(--qk-ease); }

  /* Tables -------------------------------------------------------------------- */
  /* position: relative keeps visually-hidden captions/labels inside the scroll box at 320px. */
  .table-wrap { position: relative; width: 100%; overflow-x: auto; border: 1px solid var(--qk-line); border-radius: var(--qk-radius-md); background: var(--qk-surface); }
  .table { width: 100%; border-collapse: collapse; font-size: 0.9375rem; }
  .table th { text-align: left; font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.06em; color: var(--qk-ink-500); font-weight: 700; background: var(--qk-paper); }
  .table th, .table td { padding: 0.75rem 1rem; border-bottom: 1px solid var(--qk-line); white-space: nowrap; }
  .table tr:last-child td { border-bottom: 0; }

  /* Pagination ---------------------------------------------------------------- */
  .pagination { display: flex; flex-wrap: wrap; align-items: center; justify-content: center; gap: 0.375rem; }
  .page-btn {
    display: inline-grid; place-items: center; min-width: 2.5rem; height: 2.5rem; padding: 0 0.75rem; border-radius: var(--qk-radius-sm);
    border: 1.5px solid var(--qk-line-strong); background: var(--qk-surface); color: var(--qk-ink-800); font: inherit; font-weight: 700; font-size: 0.9rem; cursor: pointer;
  }
  .page-btn:hover:not([disabled]) { border-color: var(--qk-ink-400); }
  .page-btn[aria-current="page"] { background: var(--qk-ink-900); border-color: var(--qk-ink-900); color: #fff; }
  .page-btn[disabled] { opacity: 0.45; cursor: not-allowed; }

  /* Progress ------------------------------------------------------------------ */
  .progress { height: 0.625rem; border-radius: var(--qk-radius-pill); background: var(--qk-paper-deep); overflow: hidden; }
  .progress > span { display: block; height: 100%; border-radius: inherit; background: linear-gradient(90deg, var(--qk-brand-500), var(--qk-brand-400)); transition: width 600ms var(--qk-ease); }

  /* Outline (course structure) ------------------------------------------------- */
  .outline-module { border: 1px solid var(--qk-line); border-radius: var(--qk-radius-lg); background: var(--qk-surface); overflow: hidden; }
  .outline-module + .outline-module { margin-top: 0.75rem; }
  .outline-module > summary {
    display: flex; align-items: center; gap: 1rem; padding: 1rem 1.125rem; cursor: pointer; list-style: none;
  }
  .outline-module > summary::-webkit-details-marker { display: none; }
  .outline-module > summary:hover { background: var(--qk-paper); }
  .outline-module > summary .chev { margin-left: auto; transition: transform var(--qk-base) var(--qk-ease); color: var(--qk-ink-500); }
  .outline-module[open] > summary .chev { transform: rotate(180deg); }
  .outline-index {
    display: grid; place-items: center; flex: none; width: 2.25rem; height: 2.25rem; border-radius: var(--qk-radius-sm);
    background: var(--qk-brand-50); color: var(--qk-brand-700); font-weight: 800; font-family: var(--qk-font-display);
  }
  .outline-topic { display: flex; align-items: center; gap: 0.75rem; padding: 0.75rem 1.125rem 0.75rem 1.25rem; border-top: 1px solid var(--qk-line); font-size: 0.9375rem; }
  .outline-topic .dot { width: 0.5rem; height: 0.5rem; border-radius: 50%; background: var(--qk-line-strong); flex: none; margin-left: 0.85rem; }

  /* Long-form text */
  .prose-qk { max-width: 68ch; color: var(--qk-ink-800); font-size: 1.0625rem; line-height: 1.75; }
  .prose-qk h2 { font-size: 1.5rem; margin: 2.25rem 0 0.75rem; }
  .prose-qk h3 { font-size: 1.1875rem; margin: 1.75rem 0 0.5rem; }
  .prose-qk p, .prose-qk ul, .prose-qk ol { margin: 0 0 1rem; }
  .prose-qk ul, .prose-qk ol { padding-left: 1.4rem; }
  .prose-qk li + li { margin-top: 0.35rem; }
  .prose-qk table { width: 100%; border-collapse: collapse; margin: 1rem 0; font-size: 0.95rem; display: block; overflow-x: auto; }
  .prose-qk th, .prose-qk td { border: 1px solid var(--qk-line); padding: 0.5rem 0.75rem; text-align: left; }

  /* Lesson blocks (assets/js/blocks.js) ------------------------------------------ */
  .lesson-blocks { overflow-wrap: break-word; }
  .lesson-blocks > * + * { margin-top: 1.1rem; }
  .lesson-blocks > :is(p, ul, ol) { margin-bottom: 0; }
  /* Consecutive paragraphs (one per pasted line) read as separate, well-spaced paragraphs. */
  .lesson-blocks > p { text-wrap: pretty; }
  .lesson-blocks > p + p { margin-top: 0.9rem; }
  .lesson-blocks .lesson-heading { margin: 2.25rem 0 0.25rem; color: var(--qk-ink-950); line-height: 1.25; text-wrap: balance; }
  .lesson-blocks > .lesson-heading:first-child { margin-top: 0; }
  .lesson-blocks h2.lesson-heading { font-size: 1.5rem; padding-top: 0.25rem; }
  .lesson-blocks h2.lesson-heading::before { content: ""; display: block; width: 2.5rem; height: 0.25rem; margin-bottom: 0.6rem; border-radius: 999px; background: var(--qk-brand-500); }
  .lesson-blocks h3.lesson-heading { font-size: 1.25rem; }
  .lesson-blocks h4.lesson-heading { font-size: 1.0625rem; }
  .lesson-blocks ul { list-style: disc; } .lesson-blocks ol { list-style: decimal; }
  .lesson-blocks :is(ul, ol) { padding-left: 1.5rem; }
  .lesson-blocks li { padding-left: 0.25rem; }
  .lesson-blocks li + li { margin-top: 0.5rem; }
  .lesson-blocks li::marker { color: var(--qk-brand-700); font-weight: 700; }
  .lesson-blocks code { font-family: var(--qk-font-mono); font-size: 0.9em; background: var(--qk-paper-deep); padding: 0.1em 0.35em; border-radius: 6px; }
  .lesson-table { overflow-x: auto; border: 1px solid var(--qk-line); border-radius: var(--qk-radius-md); background: var(--qk-surface); }
  /* The scroll box is the wrapper; the table itself stays a real table so its caption spans the full width. */
  .lesson-table table { display: table; width: 100%; margin: 0; border-collapse: collapse; font-size: 0.95rem; }
  .lesson-table caption { caption-side: top; text-align: left; padding: 0.6rem 0.9rem; font-weight: 700; color: var(--qk-ink-700); }
  .lesson-table th, .lesson-table td { padding: 0.55rem 0.9rem; border-top: 1px solid var(--qk-line); text-align: left; vertical-align: top; }
  .lesson-table th { background: var(--qk-paper); font-weight: 700; }
  .lesson-figure { margin: 1.75rem 0; text-align: center; }
  .lesson-figure img { display: block; max-width: 100%; max-height: min(28rem, 70vh); width: auto; height: auto; margin: 0 auto; object-fit: contain; border-radius: var(--qk-radius-md); border: 1px solid var(--qk-line); background: var(--qk-surface); }
  .lesson-figure figcaption { margin: 0.6rem auto 0; max-width: 52ch; font-size: 0.875rem; line-height: 1.5; color: var(--qk-ink-600); }
  .callout { border-radius: var(--qk-radius-lg); padding: 1rem 1.15rem; border: 1.5px solid var(--qk-line); border-left-width: 5px; background: var(--qk-surface); }
  .lesson-blocks > .callout { margin-top: 1.5rem; }
  .lesson-blocks > .callout + * { margin-top: 1.5rem; }
  @media (min-width: 640px) { .callout { padding: 1.15rem 1.4rem; } }
  .callout-title { display: flex; align-items: center; gap: 0.5rem; margin: 0 0 0.5rem; font-weight: 800; font-family: var(--qk-font-display); color: var(--qk-ink-950); line-height: 1.3; }
  .callout-title .icon { flex: none; }
  .callout-body { margin: 0; }
  .callout-body > p { margin: 0; }
  .callout-body > p + p { margin-top: 0.6rem; }
  .callout-real-world { background: var(--qk-sun-50); border-color: var(--qk-sun-200); border-left-color: var(--qk-sun-400); } .callout-real-world .callout-title .icon { color: var(--qk-sun-700); }
  .callout-example { background: var(--qk-brand-50); border-color: var(--qk-brand-100); border-left-color: var(--qk-brand-500); } .callout-example .callout-title .icon { color: var(--qk-brand-700); }
  .callout-tip { background: var(--qk-info-bg); border-color: #c8d9f5; border-left-color: var(--qk-info); } .callout-tip .callout-title .icon { color: var(--qk-info); }
  .callout-warning { background: var(--qk-warning-bg); border-color: #f6dca4; border-left-color: var(--qk-warning); } .callout-warning .callout-title .icon { color: var(--qk-warning); }
  .callout-summary { background: var(--qk-brand-900); border-color: var(--qk-brand-900); border-left-color: var(--qk-sun-300); color: #e3f5ee; }
  .callout-summary .callout-title { color: #fff; } .callout-summary .callout-title .icon { color: var(--qk-sun-300); }
  .math-block { display: block; overflow-x: auto; padding: 0.9rem 1rem; text-align: center; border-radius: var(--qk-radius-md); background: var(--qk-surface); border: 1px solid var(--qk-line); }
  .math { font-family: "Cambria Math", "STIX Two Math", "Times New Roman", serif; font-size: 1.25em; white-space: nowrap; }
  .math .mvar { font-style: italic; }
  .math .mop { padding: 0 0.22em; }
  .math sup, .math sub { font-size: 0.7em; line-height: 0; }
  .mfrac { display: inline-flex; flex-direction: column; vertical-align: middle; text-align: center; margin: 0 0.15em; }
  .mfrac .mnum { border-bottom: 1.5px solid currentColor; padding: 0 0.2em; font-size: 0.85em; }
  .mfrac .mden { padding: 0 0.2em; font-size: 0.85em; }
  .msqrt { display: inline-flex; align-items: stretch; } .msqrt-body { border-top: 1.5px solid currentColor; padding: 0 0.15em; }
  .mtext { font-family: var(--qk-font-sans); font-style: normal; font-size: 0.85em; }

  /* Decorative */
  .dot-grid { background-image: radial-gradient(var(--qk-line-strong) 1.2px, transparent 1.2px); background-size: 18px 18px; }
  .squiggle { text-decoration: underline; text-decoration-color: var(--qk-sun-400); text-decoration-thickness: 0.18em; text-underline-offset: 0.12em; text-decoration-skip-ink: none; }
}

@keyframes qk-spin { to { transform: rotate(360deg); } }
@keyframes qk-shimmer { to { transform: translateX(100%); } }
@keyframes qk-rise { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }
@keyframes qk-pop { from { opacity: 0; transform: translateY(6px) scale(0.98); } to { opacity: 1; transform: none; } }
@keyframes qk-fade-up { from { opacity: 0; transform: translateY(12px); } to { opacity: 1; transform: none; } }

.reveal { animation: qk-fade-up 520ms var(--qk-ease) both; }
.reveal-delay-1 { animation-delay: 80ms; }
.reveal-delay-2 { animation-delay: 160ms; }
.reveal-delay-3 { animation-delay: 240ms; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
  .btn:hover, .card-link:hover { transform: none; }
}

@media print {
  .site-header, .site-footer, .toast-region, .skip-link { display: none !important; }
  body { background: #fff; }
}