/* ==========================================================================
   AME · global.css
   Design foundation for ame.medkronos.com — a medical study platform.

   Contents
   1.  Design tokens (custom properties) + legacy aliases
   2.  Dark theme — explicit [data-theme] + system preference
   3.  Reset
   4.  Base elements & typography
   5.  Links · media · code · tables · forms · hr
   6.  Selection · focus · scrollbars
   7.  Layout & helper utilities
   8.  Article breakout boxes
   9.  App shell — topbar · searchbar · dropdowns · footer
   10. Page components — hero · stats · library · lesson · exam · flashcards
   11. Overlays — modal backdrop · auth slider · docs popup
   12. Ambient background & scroll-reveal hooks
   13. Reduced motion
   ========================================================================== */


/* --------------------------------------------------------------------------
   1. Design tokens
   -------------------------------------------------------------------------- */
:root {
  /* ---- Brand palette ----------------------------------------------------
     Each hue ships five companions:
     -light  → pale tint / dark-mode translucent overlay (surfaces, chips)
     -dark   → deep shade (borders, emphasis on light surfaces)
     -muted  → desaturated mid-tone (secondary details)
     -hover  → theme-aware interactive hover (darkens in light, lifts in dark)
     -bright → theme-aware text-on-tint (badges, alerts, breakout titles)
  ------------------------------------------------------------------------ */
  --color-primary: #1a5276;          /* deep medical blue */
  --color-primary-light: #d4e6f1;
  --color-primary-dark: #113a54;
  --color-primary-muted: #6289a3;
  --color-primary-hover: #113a54;
  --color-primary-bright: #1a5276;

  --color-secondary: #148f77;        /* teal */
  --color-secondary-light: #d1f2eb;
  --color-secondary-dark: #0e6655;
  --color-secondary-muted: #58a898;
  --color-secondary-hover: #0e6655;
  --color-secondary-bright: #0e6655;

  --color-accent: #d4ac0d;           /* warm amber — high yield */
  --color-accent-light: #fcf3cf;
  --color-accent-dark: #9a7d0a;
  --color-accent-muted: #cdb35a;
  --color-accent-hover: #b7950b;
  --color-accent-bright: #7d6608;

  --color-success: #27ae60;
  --color-success-light: #d5f5e3;
  --color-success-dark: #1e8449;
  --color-success-muted: #6fbd8f;
  --color-success-hover: #1e8449;
  --color-success-bright: #1e8449;

  --color-warning: #e67e22;
  --color-warning-light: #fdebd0;
  --color-warning-dark: #af601a;
  --color-warning-muted: #e3a264;
  --color-warning-hover: #af601a;
  --color-warning-bright: #af601a;

  --color-danger: #c0392b;
  --color-danger-light: #fadbd8;
  --color-danger-dark: #922b21;
  --color-danger-muted: #c97b71;
  --color-danger-hover: #922b21;
  --color-danger-bright: #922b21;

  --color-info: #2980b9;
  --color-info-light: #d6eaf8;
  --color-info-dark: #1f618d;
  --color-info-muted: #6c9fc0;
  --color-info-hover: #1f618d;
  --color-info-bright: #1f618d;

  /* ---- Light-theme surfaces ------------------------------------------ */
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-tertiary: #e9ecef;
  --text-primary: #212529;
  --text-secondary: #6c757d;
  --text-muted: #adb5bd;
  --border: #dee2e6;

  --color-link: var(--color-primary);
  --color-link-hover: var(--color-primary-dark);

  /* ---- Spacing scale -------------------------------------------------- */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 12px;
  --space-lg: 16px;
  --space-xl: 24px;
  --space-xxl: 32px;
  --space-3xl: 48px;
  --space-4xl: 64px;

  /* ---- Type scale ------------------------------------------------------ */
  --font-xs: 0.75rem;     /* 12px — captions, meta          */
  --font-sm: 0.875rem;    /* 14px — UI, tables, references  */
  --font-md: 1rem;        /* 16px — body baseline           */
  --font-lg: 1.125rem;    /* 18px — lead, h5                */
  --font-xl: 1.5rem;      /* 24px — h3                      */
  --font-xxl: 2.5rem;     /* 40px — h1                      */
  --font-3xl: 3rem;       /* display                        */
  --font-4xl: 3.75rem;    /* hero display                   */

  /* ---- Font stacks ------------------------------------------------------ */
  --font-sans: 'Source Sans 3', -apple-system, BlinkMacSystemFont, 'Segoe UI',
               Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-serif: 'Source Serif 4', Georgia, 'Times New Roman', serif;
  --font-mono: ui-monospace, 'SF Mono', 'Cascadia Mono', 'Roboto Mono',
               Menlo, Consolas, monospace;

  /* ---- Radii ------------------------------------------------------------ */
  --radius-xs: 2px;
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --radius-xl: 12px;
  --radius-xxl: 24px;
  --radius-full: 9999px;

  /* ---- Z-index layers ---------------------------------------------------- */
  --z-base: 1;
  --z-dropdown: 100;
  --z-sticky: 200;
  --z-overlay: 300;
  --z-modal: 400;
  --z-popup: 500;
  --z-toast: 600;

  /* ---- Elevation --------------------------------------------------------- */
  --shadow-sm: 0 1px 2px rgba(16, 24, 40, 0.06),
               0 1px 3px rgba(16, 24, 40, 0.10);
  --shadow-md: 0 4px 6px -2px rgba(16, 24, 40, 0.08),
               0 12px 16px -4px rgba(16, 24, 40, 0.12);
  --shadow-lg: 0 12px 24px -6px rgba(16, 24, 40, 0.12),
               0 24px 48px -12px rgba(16, 24, 40, 0.18);

  /* ---- Motion ------------------------------------------------------------- */
  --transition-fast: 150ms;
  --transition-normal: 300ms;
  --transition-slow: 500ms;
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);

  /* ---- Component-level tokens ---------------------------------------------- */
  --header-bg: rgba(255, 255, 255, 0.92);
  --overlay-bg: rgba(15, 18, 30, 0.55);
  --tooltip-bg: #212529;
  --tooltip-color: #ffffff;
  --skeleton-sheen: rgba(255, 255, 255, 0.55);
  --container-max: 1200px;

  /* ---- Legacy aliases --------------------------------------------------------
     The app shell (layout.php and views) predates the token rename. These map
     the old names onto the canonical theme-aware variables above, so shell
     styles follow the active theme automatically. New code should use the
     canonical names. */
  --bg: var(--bg-secondary);
  --surface: var(--bg-primary);
  --surface-2: var(--bg-tertiary);
  --text: var(--text-primary);
  --accent: var(--color-link);
  --accent-hover: var(--color-link-hover);
  --accent-contrast: #ffffff;
  --danger: var(--color-danger);
  --success: var(--color-success);
  --shadow: var(--shadow-md);
  --radius: var(--radius-xl);
  --maxw: 1120px;
  --topbar-h: 64px;
}


/* --------------------------------------------------------------------------
   2. Dark theme
   Applied explicitly via <html data-theme="dark"> (theme toggle in main.js),
   or automatically when the OS prefers dark — unless pinned to light via
   data-theme="light".
   -------------------------------------------------------------------------- */
[data-theme='dark'] {
  --bg-primary: #1a1a2e;
  --bg-secondary: #16213e;
  --bg-tertiary: #0f3460;
  --text-primary: #e8e8e8;
  --text-secondary: #b0b0b0;
  --text-muted: #707070;
  --border: #2a2a4a;

  --color-link: #5dade2;
  --color-link-hover: #85c1e9;

  /* Pale tints become translucent overlays on dark surfaces */
  --color-primary-light: rgba(52, 152, 219, 0.16);
  --color-secondary-light: rgba(26, 188, 156, 0.16);
  --color-accent-light: rgba(241, 196, 15, 0.14);
  --color-success-light: rgba(46, 204, 113, 0.16);
  --color-warning-light: rgba(243, 156, 18, 0.16);
  --color-danger-light: rgba(231, 76, 60, 0.16);
  --color-info-light: rgba(52, 152, 219, 0.16);

  /* Text-on-tint brightens for contrast on dark chips/alerts */
  --color-primary-bright: #7fb3d5;
  --color-secondary-bright: #58c4ad;
  --color-accent-bright: #f4d03f;
  --color-success-bright: #58d68d;
  --color-warning-bright: #eb984e;
  --color-danger-bright: #ec7063;
  --color-info-bright: #5dade2;

  /* Hovers lift brighter instead of darkening */
  --color-primary-hover: #2e86c1;
  --color-secondary-hover: #1abc9c;
  --color-accent-hover: #f1c40f;
  --color-success-hover: #2ecc71;
  --color-warning-hover: #f39c12;
  --color-danger-hover: #e74c3c;
  --color-info-hover: #3498db;

  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.40),
               0 1px 3px rgba(0, 0, 0, 0.50);
  --shadow-md: 0 4px 6px -2px rgba(0, 0, 0, 0.45),
               0 12px 16px -4px rgba(0, 0, 0, 0.50);
  --shadow-lg: 0 12px 24px -6px rgba(0, 0, 0, 0.50),
               0 24px 48px -12px rgba(0, 0, 0, 0.60);

  --header-bg: rgba(26, 26, 46, 0.92);
  --overlay-bg: rgba(5, 8, 18, 0.70);
  --tooltip-bg: #e8e8e8;
  --tooltip-color: #1a1a2e;
  --skeleton-sheen: rgba(255, 255, 255, 0.07);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme='light']) {
    --bg-primary: #1a1a2e;
    --bg-secondary: #16213e;
    --bg-tertiary: #0f3460;
    --text-primary: #e8e8e8;
    --text-secondary: #b0b0b0;
    --text-muted: #707070;
    --border: #2a2a4a;

    --color-link: #5dade2;
    --color-link-hover: #85c1e9;

    --color-primary-light: rgba(52, 152, 219, 0.16);
    --color-secondary-light: rgba(26, 188, 156, 0.16);
    --color-accent-light: rgba(241, 196, 15, 0.14);
    --color-success-light: rgba(46, 204, 113, 0.16);
    --color-warning-light: rgba(243, 156, 18, 0.16);
    --color-danger-light: rgba(231, 76, 60, 0.16);
    --color-info-light: rgba(52, 152, 219, 0.16);

    --color-primary-bright: #7fb3d5;
    --color-secondary-bright: #58c4ad;
    --color-accent-bright: #f4d03f;
    --color-success-bright: #58d68d;
    --color-warning-bright: #eb984e;
    --color-danger-bright: #ec7063;
    --color-info-bright: #5dade2;

    --color-primary-hover: #2e86c1;
    --color-secondary-hover: #1abc9c;
    --color-accent-hover: #f1c40f;
    --color-success-hover: #2ecc71;
    --color-warning-hover: #f39c12;
    --color-danger-hover: #e74c3c;
    --color-info-hover: #3498db;

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.40),
                 0 1px 3px rgba(0, 0, 0, 0.50);
    --shadow-md: 0 4px 6px -2px rgba(0, 0, 0, 0.45),
                 0 12px 16px -4px rgba(0, 0, 0, 0.50);
    --shadow-lg: 0 12px 24px -6px rgba(0, 0, 0, 0.50),
                 0 24px 48px -12px rgba(0, 0, 0, 0.60);

    --header-bg: rgba(26, 26, 46, 0.92);
    --overlay-bg: rgba(5, 8, 18, 0.70);
    --tooltip-bg: #e8e8e8;
    --tooltip-color: #1a1a2e;
    --skeleton-sheen: rgba(255, 255, 255, 0.07);
  }
}


/* --------------------------------------------------------------------------
   3. Reset
   -------------------------------------------------------------------------- */
*,
*::before,
*::after {
  box-sizing: border-box;
}

* {
  margin: 0;
  padding: 0;
}

/* main.js toggles panels with the hidden attribute — keep it authoritative
   even on elements with an explicit display (e.g. .nav-dropdown). */
[hidden] {
  display: none !important;
}

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

@media (prefers-reduced-motion: no-preference) {
  html {
    scroll-behavior: smooth;
  }
}

img,
picture,
video,
canvas,
svg {
  display: block;
  max-width: 100%;
}

input,
button,
textarea,
select {
  font: inherit;
  color: inherit;
}

button {
  cursor: pointer;
  background: none;
  border: none;
}

summary {
  cursor: pointer;
}


/* --------------------------------------------------------------------------
   4. Base elements & typography
   Body copy is set in Source Serif 4 for long study sessions; all UI and
   headings use Source Sans 3 for clinical clarity.
   -------------------------------------------------------------------------- */
body {
  min-height: 100vh;
  min-height: 100dvh;
  display: flex;                 /* app shell: topbar / content / footer */
  flex-direction: column;
  font-family: var(--font-serif);
  font-size: var(--font-md);
  font-weight: 400;
  line-height: 1.7;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  transition: background-color var(--transition-normal),
              color var(--transition-normal);
}

h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-sans);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.015em;
  color: var(--text-primary);
  margin: 0 0 var(--space-lg);
  text-wrap: balance;
}

h1 {
  font-size: var(--font-xxl);   /* 2.5rem  */
  letter-spacing: -0.025em;
}

h2 {
  font-size: 2rem;
}

h3 {
  font-size: var(--font-xl);    /* 1.5rem  */
}

h4 {
  font-size: 1.25rem;
}

h5 {
  font-size: var(--font-lg);    /* 1.125rem */
}

h6 {
  font-size: var(--font-md);    /* 1rem     */
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* Breathing room before subsequent headings in long-form articles */
:where(h2, h3, h4):not(:first-child) {
  margin-top: var(--space-xxl);
}

p {
  margin: 0 0 var(--space-lg);
  line-height: 1.75;
  orphans: 2;
  widows: 2;
}

p:last-child {
  margin-bottom: 0;
}

.lead {
  font-size: var(--font-lg);
  color: var(--text-secondary);
  max-width: 60ch;
}

small {
  font-size: 0.875em;
}

strong,
b {
  font-weight: 600;
}

ul,
ol {
  margin: 0 0 var(--space-lg);
  padding-left: 1.5em;
}

ul:last-child,
ol:last-child {
  margin-bottom: 0;
}

li {
  margin-bottom: var(--space-xs);
  line-height: 1.65;
}

li > ul,
li > ol {
  margin: var(--space-xs) 0 0;
}

blockquote {
  margin: 0 0 var(--space-lg);
  padding: var(--space-xs) var(--space-lg);
  border-left: 3px solid var(--color-accent);
  color: var(--text-secondary);
  font-style: italic;
}

/* Anchor targets clear the sticky topbar */
[id] {
  scroll-margin-top: calc(var(--topbar-h) + 24px);
}


/* --------------------------------------------------------------------------
   5. Links · media · code · tables · forms · hr
   -------------------------------------------------------------------------- */
a {
  color: var(--color-link);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.15em;
  transition: color var(--transition-fast),
              text-decoration-color var(--transition-fast);
}

a:hover {
  color: var(--color-link-hover);
  text-decoration-thickness: 2px;
}

img {
  height: auto;
  border-radius: var(--radius-md);
}

figure {
  margin: var(--space-xl) 0;
}

figcaption {
  margin-top: var(--space-sm);
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  color: var(--text-secondary);
}

code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background: var(--bg-tertiary);
  border-radius: var(--radius-sm);
  padding: 0.15em 0.4em;
}

pre {
  font-family: var(--font-mono);
  font-size: var(--font-sm);
  line-height: 1.6;
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin: 0 0 var(--space-lg);
  overflow: auto;
  tab-size: 2;
}

pre code {
  background: none;
  border-radius: 0;
  padding: 0;
  font-size: inherit;
}

kbd {
  font-family: var(--font-mono);
  font-size: 0.85em;
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-bottom-width: 2px;
  border-radius: var(--radius-sm);
  padding: 0.1em 0.45em;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: 0 0 var(--space-lg);
  font-family: var(--font-sans);
  font-size: var(--font-sm);
}

caption {
  caption-side: bottom;
  padding-top: var(--space-sm);
  font-size: var(--font-xs);
  color: var(--text-muted);
  text-align: left;
}

th,
td {
  padding: var(--space-sm) var(--space-md);
  text-align: left;
  vertical-align: top;
  border-bottom: 1px solid var(--border);
}

th {
  font-weight: 600;
  color: var(--text-primary);
  background: var(--bg-secondary);
}

tbody tr {
  transition: background-color var(--transition-fast);
}

tbody tr:hover {
  background: var(--bg-secondary);
}

fieldset {
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  margin: 0 0 var(--space-lg);
}

legend {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: var(--font-sm);
  padding: 0 var(--space-xs);
}

::placeholder {
  color: var(--text-muted);
  opacity: 1;
}

hr {
  border: none;
  height: 1px;
  background: var(--border);
  margin: var(--space-xxl) 0;
}


/* --------------------------------------------------------------------------
   6. Selection · focus · scrollbars
   -------------------------------------------------------------------------- */
::selection {
  background: var(--color-accent);
  color: #1a1a2e;
}

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

* {
  scrollbar-width: thin;
  scrollbar-color: var(--border) transparent;
}

::-webkit-scrollbar {
  width: 10px;
  height: 10px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

::-webkit-scrollbar-thumb {
  background-color: var(--border);
  border-radius: var(--radius-full);
  border: 2px solid transparent;
  background-clip: padding-box;
}

::-webkit-scrollbar-thumb:hover {
  background-color: var(--text-muted);
}


/* --------------------------------------------------------------------------
   7. Layout & helper utilities
   -------------------------------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--space-lg);
}

/* Main page column used by layout.php */
.content {
  width: 100%;
  max-width: var(--maxw);
  margin: 0 auto;
  padding: var(--space-xl) var(--space-xl) var(--space-4xl);
  flex: 1;
}

.flex {
  display: flex;
}

.flex-col {
  display: flex;
  flex-direction: column;
}

.flex-wrap {
  flex-wrap: wrap;
}

.items-center {
  align-items: center;
}

.items-start {
  align-items: flex-start;
}

.justify-between {
  justify-content: space-between;
}

.justify-center {
  justify-content: center;
}

.gap-sm {
  gap: var(--space-sm);
}

.gap-md {
  gap: var(--space-md);
}

.gap-lg {
  gap: var(--space-lg);
}

.gap-xl {
  gap: var(--space-xl);
}

.text-center {
  text-align: center;
}

.text-muted,
.muted {
  color: var(--text-muted);
}

.text-small,
.small {
  font-size: 0.85rem;
}

.hidden {
  display: none !important;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

/* Friendly empty states */
.empty {
  padding: var(--space-xxl);
  text-align: center;
  color: var(--text-muted);
  background: var(--surface-2);
  border: 1px dashed var(--border);
  border-radius: var(--radius);
}


/* --------------------------------------------------------------------------
   8. Article breakout boxes
   Visual triage for study content:
   update     → blue   — medical updates / revised guidance
   important  → amber  — high-yield material
   warning    → orange — don't-miss distinctions & pitfalls
   reference  → gray   — citations & further reading
   -------------------------------------------------------------------------- */
.breakout-update,
.breakout-important,
.breakout-warning,
.breakout-reference {
  margin: var(--space-xl) 0;
  padding: var(--space-lg) var(--space-xl);
  border-left: 4px solid var(--border);
  border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
  background: var(--bg-secondary);
}

.breakout-update > :last-child,
.breakout-important > :last-child,
.breakout-warning > :last-child,
.breakout-reference > :last-child {
  margin-bottom: 0;
}

/* Optional small-caps label inside any breakout, e.g.
   <span class="breakout-title">High yield</span> */
.breakout-title {
  display: block;
  margin-bottom: var(--space-sm);
  font-family: var(--font-sans);
  font-size: var(--font-xs);
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.breakout-update {
  border-left-color: var(--color-primary);
  background: var(--color-primary-light);
}

.breakout-update .breakout-title {
  color: var(--color-primary-bright);
}

.breakout-important {
  border-left-color: var(--color-accent);
  background: var(--color-accent-light);
}

.breakout-important .breakout-title {
  color: var(--color-accent-bright);
}

.breakout-warning {
  border-left-color: var(--color-warning);
  background: var(--color-warning-light);
}

.breakout-warning .breakout-title {
  color: var(--color-warning-bright);
}

.breakout-reference {
  border-left-color: var(--text-muted);
  background: var(--bg-secondary);
  color: var(--text-secondary);
  font-size: var(--font-sm);
}

.breakout-reference .breakout-title {
  color: var(--text-secondary);
}

/* Superseded medical information — kept visible but clearly retired */
.text-outdated {
  text-decoration: line-through;
  text-decoration-color: var(--color-danger-muted);
  opacity: 0.6;
  color: var(--text-muted);
}


/* --------------------------------------------------------------------------
   9. App shell — topbar · searchbar · dropdowns · footer
   -------------------------------------------------------------------------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  height: var(--topbar-h);
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: var(--space-md);
  padding: 0 var(--space-xl);
  background: var(--header-bg);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.topbar-left {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  position: relative;
  flex-shrink: 0;
}

.topbar-center {
  display: flex;
  justify-content: center;
  min-width: 0; /* let the search shrink instead of pushing siblings out */
}

.topbar-right {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  justify-content: flex-end;
  flex-shrink: 0;
}

.logo {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-weight: 700;
  text-decoration: none;
  transition: opacity var(--transition-fast);
}

.logo:hover {
  color: var(--text-primary);
  opacity: 0.85;
}

.logo-text {
  font-size: 1.15rem;
  letter-spacing: 0.5px;
}

.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  background: transparent;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-size: 1.15rem;
  line-height: 1;
  cursor: pointer;
  transition: background-color var(--transition-fast),
              color var(--transition-fast),
              transform var(--transition-fast);
}

.icon-btn:hover {
  background: var(--surface-2);
}

.icon-btn:active {
  transform: scale(0.94);
}

/* -- Searchbar ------------------------------------------------------------ */
.searchbar {
  display: flex;
  align-items: center;
  width: 100%;
  max-width: 420px;
  min-width: 0;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  overflow: hidden;
  transition: border-color var(--transition-fast),
              box-shadow var(--transition-fast),
              background-color var(--transition-fast);
}

.searchbar:focus-within {
  background: var(--surface);
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-light);
}

.searchbar input {
  flex: 1;
  min-width: 0;
  border: 0;
  background: transparent;
  padding: 0.5rem 0.9rem;
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 0.95rem;
  outline: none;
}

.searchbar button {
  border: 0;
  background: transparent;
  color: var(--text-muted);
  padding: 0 0.9rem;
  font-size: 1.2rem;
  cursor: pointer;
  transition: color var(--transition-fast);
}

.searchbar button:hover {
  color: var(--color-primary);
}

.searchbar-big {
  width: min(640px, 90vw);
  border-radius: var(--radius);
}

.searchbar-big input {
  padding: 0.75rem 1rem;
}

.searchbar-big button {
  padding: 0 1.1rem;
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  font-weight: 600;
}

/* -- Dropdown panels (hamburger nav + user menu) ----------------------------
   Toggled via the hidden attribute in main.js. Scoped under .topbar so the
   generic .nav-dropdown wrapper pattern in ui.css stays available elsewhere. */
.topbar .nav-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  z-index: var(--z-dropdown);
  display: flex;
  flex-direction: column;
  min-width: 190px;
  padding: 0.4rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
}

.topbar .nav-dropdown:not([hidden]) {
  animation: ame-fade-in var(--transition-fast) var(--ease-out);
}

.topbar .nav-dropdown a {
  padding: 0.55rem 0.7rem;
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  font-weight: 500;
  text-decoration: none;
  transition: background-color var(--transition-fast),
              color var(--transition-fast);
}

.topbar .nav-dropdown a:hover {
  background: var(--surface-2);
  color: var(--accent);
}

.dropdown-label {
  padding: 0.4rem 0.7rem;
  font-family: var(--font-sans);
  font-size: 0.8rem;
  color: var(--text-muted);
  border-bottom: 1px solid var(--border);
  margin-bottom: 0.3rem;
  word-break: break-all;
}

.user-menu {
  position: relative;
}

.user-menu .nav-dropdown {
  left: auto;
  right: 0;
}

.user-btn {
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--text-primary);
  padding: 0.45rem 0.8rem;
  border-radius: var(--radius-full);
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  font-weight: 600;
  cursor: pointer;
  transition: border-color var(--transition-fast),
              background-color var(--transition-fast);
}

.user-btn:hover {
  border-color: var(--accent);
}

/* -- Footer ----------------------------------------------------------------- */
.footer-grid {
  max-width: var(--maxw);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 1.5rem;
}

.footer-col {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  font-family: var(--font-sans);
  font-size: var(--font-sm);
}

.footer-col h4 {
  margin-bottom: 0.3rem;
  font-size: 1rem;
}

.footer-col a {
  width: fit-content;
  color: var(--text-muted);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.footer-col a:hover {
  color: var(--accent);
}

.footer-logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.socials {
  display: flex;
  gap: 0.5rem;
  align-items: center;
  margin-top: 0.3rem;
}

.footer-bottom {
  max-width: var(--maxw);
  margin: 1.5rem auto 0;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  font-family: var(--font-sans);
  font-size: 0.85rem;
  color: var(--text-muted);
}


/* --------------------------------------------------------------------------
   10. Page components
   -------------------------------------------------------------------------- */

/* -- Page headers & breadcrumbs ------------------------------------------- */
.page-header {
  margin-bottom: var(--space-xl);
}

.page-header h1 {
  margin-bottom: var(--space-sm);
}

.breadcrumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-xs);
  margin-bottom: var(--space-sm);
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  color: var(--text-muted);
}

.breadcrumbs a {
  color: var(--text-secondary);
  text-decoration: none;
}

.breadcrumbs a:hover {
  color: var(--accent);
  text-decoration: underline;
}

.breadcrumbs .sep {
  color: var(--text-muted);
}

/* -- Hero (home) ------------------------------------------------------------ */
.hero {
  padding: var(--space-3xl) 0 var(--space-xl);
}

.hero h1 {
  font-size: clamp(2.2rem, 5vw, var(--font-3xl));
  margin-bottom: var(--space-md);
}

/* Amber study-highlighter stroke under the hero title */
.hero h1::after {
  content: '';
  display: block;
  width: 72px;
  height: 5px;
  margin-top: var(--space-sm);
  border-radius: var(--radius-full);
  background: var(--color-accent);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  margin-top: var(--space-xl);
}

/* -- Stats ------------------------------------------------------------------- */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-lg);
  margin: var(--space-xl) 0;
}

.stat-card {
  display: flex;
  flex-direction: column;
  gap: 2px;
  padding: var(--space-lg);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-fast) var(--ease-out),
              box-shadow var(--transition-fast) var(--ease-out);
}

.stat-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.stat-num {
  font-family: var(--font-sans);
  font-size: 2rem;
  font-weight: 700;
  line-height: 1.2;
  color: var(--accent);
  font-variant-numeric: tabular-nums;
}

.stat-label {
  font-family: var(--font-sans);
  font-size: var(--font-xs);
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-muted);
}

/* -- Quick links --------------------------------------------------------------- */
.quick-links {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-lg);
  margin: var(--space-xl) 0;
}

.quick-card {
  padding: var(--space-xl);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text-primary);
  text-decoration: none;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-fast) var(--ease-out),
              box-shadow var(--transition-fast) var(--ease-out),
              border-color var(--transition-fast);
}

.quick-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent-muted);
  color: var(--text-primary);
}

.quick-card h3 {
  margin-bottom: var(--space-xs);
}

.quick-card p {
  margin: 0;
  font-size: var(--font-sm);
  color: var(--text-secondary);
}

.recent {
  margin: var(--space-xxl) 0;
}

/* -- Library: book cards & lists ------------------------------------------------ */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: var(--space-lg);
}

.card-grid .card {
  color: inherit;
  text-decoration: none;
  overflow: hidden;
  transition: transform var(--transition-fast) var(--ease-out),
              box-shadow var(--transition-fast) var(--ease-out),
              border-color var(--transition-fast);
}

.card-grid .card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent-muted);
  color: inherit;
}

.card-cover {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 96px;
  font-family: var(--font-sans);
  font-size: 2.5rem;
  font-weight: 700;
  color: #ffffff;
  background: linear-gradient(135deg, var(--color-primary), var(--color-info));
}

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

.list li {
  margin-bottom: 0;
}

.list-rows > li {
  padding: var(--space-sm) 0;
  border-bottom: 1px solid var(--border);
}

.list-rows > li:last-child {
  border-bottom: 0;
}

.list-rows a {
  font-family: var(--font-sans);
  font-weight: 500;
}

.subchapter-block {
  margin-bottom: var(--space-xl);
}

.subchapter-block h3 {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.deck-link {
  text-decoration: none;
}

/* -- Anki deck browser -------------------------------------------------------------- */
.deck-book {
  margin-bottom: var(--space-xxl);
}

.deck-chapter {
  margin: var(--space-lg) 0;
}

.deck-chapter h4 {
  font-size: var(--font-sm);
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--text-secondary);
  margin-bottom: var(--space-sm);
}

.deck-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.deck-chip {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  padding: 0.45em 0.9em;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  font-weight: 500;
  text-decoration: none;
  transition: border-color var(--transition-fast),
              background-color var(--transition-fast),
              color var(--transition-fast),
              transform var(--transition-fast) var(--ease-out);
}

.deck-chip:hover {
  border-color: var(--accent);
  background: var(--color-accent-light);
  color: var(--text-primary);
  transform: translateY(-1px);
}

/* -- Lesson ------------------------------------------------------------------------ */
.lesson {
  margin: var(--space-lg) 0;
  padding: var(--space-xl) var(--space-xxl);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
}

.lesson-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}

.lesson-header h1 {
  margin: 0;
}

.lesson-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs);
}

.lesson-content {
  max-width: 74ch; /* comfortable serif measure */
}

.original-box {
  margin-top: var(--space-xl);
  padding-top: var(--space-lg);
  border-top: 1px dashed var(--border);
}

.original-content {
  margin-top: var(--space-md);
  max-height: 420px;
  white-space: pre-wrap;
}

.related-cards {
  margin: var(--space-xxl) 0;
}

.related-cards > .btn {
  margin-top: var(--space-md);
}

/* -- Flashcards (3D flip, no inner wrapper) ------------------------------------------ */
.flashcards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: var(--space-lg);
  margin: var(--space-lg) 0;
}

.flashcard {
  position: relative;
  min-height: 200px;
  perspective: 1200px;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

.fc-front,
.fc-back {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-xl);
  text-align: center;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Amber marks the question face, teal the answer */
.fc-front::before,
.fc-back::before {
  content: '';
  position: absolute;
  top: 0;
  left: 24px;
  right: 24px;
  height: 4px;
  border-radius: 0 0 var(--radius-sm) var(--radius-sm);
}

.fc-front::before {
  background: var(--color-accent);
}

.fc-back {
  background: var(--surface-2);
  transform: rotateY(180deg);
}

.fc-back::before {
  background: var(--color-secondary);
}

.flashcard.flipped .fc-front {
  transform: rotateY(-180deg);
}

.flashcard.flipped .fc-back {
  transform: rotateY(0deg);
}

/* -- Flash mode (typed answers) --------------------------------------------------------- */
.flash-quiz {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  max-width: 720px;
}

.flash-item {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-md) var(--space-lg);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color var(--transition-fast);
}

.flash-front {
  flex: 1 1 100%;
  margin: 0 0 var(--space-xs);
  font-weight: 600;
}

.flash-input {
  flex: 1 1 220px;
  padding: 0.55em 0.8em;
  background: var(--bg-primary);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  transition: border-color var(--transition-fast),
              box-shadow var(--transition-fast);
}

.flash-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-light);
}

.flash-result {
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  font-weight: 700;
}

.flash-result:empty {
  display: none;
}

.flash-item.correct,
.flash-item.correct .flash-input {
  border-color: var(--color-success);
}

.flash-item.correct .flash-result {
  color: var(--color-success-bright);
}

.flash-item.wrong,
.flash-item.wrong .flash-input {
  border-color: var(--color-danger);
}

.flash-item.wrong .flash-result {
  color: var(--color-danger-bright);
}

/* -- Exam / QBank ----------------------------------------------------------------------- */
.exam-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: var(--space-md);
  flex-wrap: wrap;
}

.exam-header h1 {
  margin: 0;
}

.exam-meta {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  flex-wrap: wrap;
}

.timer {
  padding: 0.2em 0.7em;
  font-family: var(--font-mono);
  font-size: var(--font-lg);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  color: var(--text-primary);
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
}

.exam {
  display: flex;
  flex-direction: column;
  gap: var(--space-xl);
}

.question-card {
  padding: var(--space-xl);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
}

.q-head {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  margin-bottom: var(--space-md);
}

.q-num {
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  font-weight: 700;
  letter-spacing: 0.04em;
  color: var(--accent);
}

.q-stem {
  margin-bottom: var(--space-lg);
  line-height: 1.65;
}

.q-options {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.q-option {
  display: flex;
  align-items: flex-start;
  gap: var(--space-sm);
  padding: var(--space-sm) var(--space-md);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  line-height: 1.5;
  cursor: pointer;
  transition: border-color var(--transition-fast),
              background-color var(--transition-fast);
}

.q-option:hover {
  border-color: var(--accent);
  background: var(--color-accent-light);
}

.q-option input {
  margin-top: 3px;
  accent-color: var(--color-primary);
}

.q-option:has(input:checked) {
  border-color: var(--color-primary);
  background: var(--color-primary-light);
}

.q-letter {
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 26px;
  border-radius: var(--radius-full);
  background: var(--surface-2);
  border: 1px solid var(--border);
  font-size: var(--font-xs);
  font-weight: 700;
  transition: background-color var(--transition-fast),
              color var(--transition-fast),
              border-color var(--transition-fast);
}

/* Grading states (main.js adds .correct / .wrong) */
.q-option.correct {
  border-color: var(--color-success);
  background: var(--color-success-light);
}

.q-option.correct .q-letter {
  background: var(--color-success);
  border-color: var(--color-success);
  color: #ffffff;
}

.q-option.wrong {
  border-color: var(--color-danger);
  background: var(--color-danger-light);
}

.q-option.wrong .q-letter {
  background: var(--color-danger);
  border-color: var(--color-danger);
  color: #ffffff;
}

.q-explanation {
  margin-top: var(--space-lg);
  padding: var(--space-md) var(--space-lg);
  border-left: 3px solid var(--color-secondary);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  background: var(--color-secondary-light);
  font-size: var(--font-sm);
}

.exam-footer {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
}

.exam-score {
  font-family: var(--font-sans);
  font-size: var(--font-lg);
  font-weight: 700;
}

.exam-creator {
  max-width: 640px;
}

.form-card {
  display: block;
  padding: var(--space-xl);
}

/* Bare labelled controls inside app forms (auth panels, exam creator) */
.auth-panel label,
.form-card label {
  display: block;
  margin-bottom: var(--space-lg);
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  font-weight: 600;
}

.auth-panel input:not([type='checkbox']):not([type='radio']),
.form-card input:not([type='checkbox']):not([type='radio']) {
  display: block;
  width: 100%;
  margin-top: var(--space-xs);
  padding: 0.6em 0.85em;
  font-family: var(--font-sans);
  font-size: var(--font-md);
  font-weight: 400;
  color: var(--text-primary);
  background: var(--bg-primary);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  transition: border-color var(--transition-fast),
              box-shadow var(--transition-fast);
}

.auth-panel input:not([type='checkbox']):not([type='radio']):focus,
.form-card input:not([type='checkbox']):not([type='radio']):focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px var(--color-primary-light);
}

.checkbox {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-xs) 0;
  font-weight: 500;
  cursor: pointer;
}

.checkbox input {
  accent-color: var(--color-primary);
}

/* -- Search results --------------------------------------------------------------------- */
.search-group {
  margin: var(--space-xxl) 0;
}

.search-group h2 {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding-bottom: var(--space-xs);
  border-bottom: 2px solid var(--color-accent);
  margin-bottom: var(--space-md);
}


/* --------------------------------------------------------------------------
   11. Overlays — modal backdrop · auth slider · docs popup
   main.js shows/hides .overlay panels via the hidden attribute.
   -------------------------------------------------------------------------- */
.overlay {
  position: fixed;
  inset: 0;
  z-index: var(--z-overlay);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-lg);
  background: var(--overlay-bg);
  -webkit-backdrop-filter: blur(4px);
  backdrop-filter: blur(4px);
}

.overlay:not([hidden]) .modal {
  animation: ame-modal-in var(--transition-normal) var(--ease-out);
}

@keyframes ame-modal-in {
  from {
    opacity: 0;
    transform: translateY(16px) scale(0.97);
  }
  to {
    opacity: 1;
    transform: none;
  }
}

/* Auth popup: three sliding panels driven by data-panel (auth.js) */
.modal-auth {
  max-width: 420px;
  overflow: hidden;
}

.auth-viewport {
  overflow: hidden;
}

.auth-slider {
  display: flex;
  width: 300%;
  transition: transform var(--transition-normal) var(--ease-out);
}

.auth-slider[data-panel='register'] {
  transform: translateX(calc(-100% / 3));
}

.auth-slider[data-panel='recover'] {
  transform: translateX(calc(-200% / 3));
}

.auth-panel h3 {
  margin-bottom: var(--space-lg);
}

.auth-msg {
  min-height: 1.3em;
  margin: var(--space-sm) 0 0;
  font-family: var(--font-sans);
  font-size: var(--font-sm);
  font-weight: 600;
  color: var(--color-danger);
}

.auth-msg.ok,
.auth-msg.success {
  color: var(--color-success-bright);
}

.auth-msg.error {
  color: var(--color-danger-bright);
}

/* Docs & versioning popup */
.docs-body {
  max-height: 60vh;
  overflow-y: auto;
}

.docs-pane {
  display: none;
}

.docs-pane.active {
  display: block;
  animation: ame-fade-in var(--transition-normal) var(--ease-out);
}

@keyframes ame-fade-in {
  from {
    opacity: 0;
    transform: translateY(6px);
  }
  to {
    opacity: 1;
    transform: none;
  }
}


/* --------------------------------------------------------------------------
   12. Ambient background & scroll-reveal hooks
   -------------------------------------------------------------------------- */

/* Soft layered wash for hero / auth screens. Theme-aware via -light tokens. */
.bg-ambient {
  background:
    radial-gradient(1000px 520px at 85% -10%, var(--color-primary-light) 0%, transparent 60%),
    radial-gradient(820px 420px at -10% 110%, var(--color-accent-light) 0%, transparent 55%),
    var(--bg-primary);
}

/* JS adds .visible when the element scrolls into view */
.reveal {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity var(--transition-slow) var(--ease-out),
              transform var(--transition-slow) var(--ease-out);
}

.reveal.visible {
  opacity: 1;
  transform: none;
}


/* --------------------------------------------------------------------------
   13. Reduced motion
   -------------------------------------------------------------------------- */
@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;
  }

  .reveal {
    opacity: 1;
    transform: none;
  }
}

/* ==========================================================================
   14. Avatar button (person circle) — replaces login/register button
   ========================================================================== */
.avatar-btn {
  width: 38px;
  height: 38px;
  border-radius: var(--radius-full, 9999px);
  border: 2px solid var(--border, #dee2e6);
  background: var(--bg-secondary, #f8f9fa);
  color: var(--text-secondary, #6c757d);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  padding: 0;
  transition: border-color var(--transition-fast, 150ms),
              color var(--transition-fast, 150ms),
              background var(--transition-fast, 150ms),
              transform var(--transition-fast, 150ms);
  flex-shrink: 0;
}
.avatar-btn:hover {
  border-color: var(--accent, #4f8cff);
  color: var(--accent, #4f8cff);
  transform: translateY(-1px);
}
.avatar-btn svg { display: block; }
.avatar-btn.avatar-authed {
  background: var(--accent, #4f8cff);
  border-color: var(--accent, #4f8cff);
  color: #fff;
}
.avatar-btn.avatar-authed:hover { filter: brightness(1.08); color: #fff; }

/* ==========================================================================
   15. Toast notifications (top-fixed, auto-dismiss)
   ========================================================================== */
.toast-region {
  position: fixed;
  top: var(--space-lg, 24px);
  left: 50%;
  transform: translateX(-50%);
  z-index: var(--z-toast, 600);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm, 8px);
  width: min(92vw, 420px);
  pointer-events: none;
}
.toast {
  pointer-events: auto;
  display: flex;
  align-items: center;
  gap: var(--space-sm, 8px);
  padding: var(--space-md, 16px) var(--space-lg, 24px);
  border-radius: var(--radius-md, 10px);
  background: var(--bg-primary, #fff);
  color: var(--text-primary, #212529);
  border: 1px solid var(--border, #dee2e6);
  border-left: 4px solid var(--info, #2980b9);
  box-shadow: var(--shadow-lg, 0 10px 30px rgba(0,0,0,.15));
  font-size: var(--font-sm, .9rem);
  font-weight: 500;
  animation: toast-in .35s cubic-bezier(.21,1.02,.55,1.01) forwards;
}
.toast.toast-out { animation: toast-out .4s ease forwards; }
.toast-error   { border-left-color: var(--danger, #c0392b); }
.toast-success { border-left-color: var(--success, #27ae60); }
.toast-warning { border-left-color: var(--warning, #e67e22); }
.toast-info    { border-left-color: var(--info, #2980b9); }
.toast-icon { font-size: 1.1em; line-height: 1; }
@keyframes toast-in {
  from { opacity: 0; transform: translateY(-140%); }
  to   { opacity: 1; transform: translateY(0); }
}
@keyframes toast-out {
  from { opacity: 1; transform: translateY(0); }
  to   { opacity: 0; transform: translateY(-140%); }
}

/* ==========================================================================
   16. Error page
   ========================================================================== */
.error-wrap {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--space-xl, 48px) var(--space-lg, 24px);
  background:
    radial-gradient(circle at 20% 20%, color-mix(in srgb, var(--accent, #4f8cff) 8%, transparent), transparent 45%),
    var(--bg-secondary, #f8f9fa);
}
.error-code {
  font-family: var(--font-sans, sans-serif);
  font-size: clamp(5rem, 22vw, 12rem);
  font-weight: 800;
  line-height: .9;
  letter-spacing: -.04em;
  background: linear-gradient(135deg, var(--accent, #4f8cff), var(--primary, #1a5276));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  margin: 0;
}
.error-title {
  font-family: var(--font-serif, serif);
  font-size: clamp(1.4rem, 4vw, 2rem);
  margin: var(--space-md, 16px) 0 var(--space-sm, 8px);
  color: var(--text-primary, #212529);
}
.error-detail {
  color: var(--text-secondary, #6c757d);
  max-width: 46ch;
  margin: 0 auto var(--space-lg, 24px);
  font-size: var(--font-sm, .9rem);
  word-break: break-word;
}
.error-ekg { width: min(320px, 70vw); margin: var(--space-md, 16px) 0; opacity: .5; }
.error-actions { display: flex; gap: var(--space-sm, 8px); flex-wrap: wrap; justify-content: center; }

/* ==========================================================================
   17. Feedback popup extras
   ========================================================================== */
.feedback-stars { display: flex; gap: var(--space-xs, 4px); font-size: 1.8rem; margin: var(--space-sm, 8px) 0; }
.feedback-stars button {
  background: none; border: none; cursor: pointer; padding: 2px;
  color: var(--text-muted, #adb5bd); transition: color .15s, transform .15s;
}
.feedback-stars button:hover { transform: scale(1.15); }
.feedback-stars button.active { color: var(--accent, #f0b429); }

/* ==========================================================================
   18. QBank book selection actions
   ========================================================================== */
.book-actions {
  display: flex;
  align-items: center;
  gap: var(--space-sm, 8px);
  flex-wrap: wrap;
  margin-top: var(--space-sm, 8px);
}

/* ==========================================================================
   19. Button rows — flex multiple buttons on one line, evenly sized
   ========================================================================== */
.btn-row {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm, 8px);
  align-items: stretch;
}
.btn-row > .btn { flex: 1 1 auto; text-align: center; }
.btn-row.btn-row-equal > .btn { flex: 1 1 0; }

/* ==========================================================================
   20. Article references + in-text citation links
   ========================================================================== */
.references ol {
  margin: 0;
  padding-left: 1.4em;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm, 8px);
  counter-reset: ref;
}
.references li {
  font-size: var(--font-sm, .9rem);
  line-height: 1.6;
  color: var(--text-secondary, #6c757d);
  scroll-margin-top: calc(var(--topbar-h, 64px) + 16px);
  padding: 2px 6px;
  border-radius: var(--radius-sm, 6px);
  transition: background-color .3s;
}
.references li:target,
.references li.ref-highlight {
  background: color-mix(in srgb, var(--accent, #4f8cff) 12%, transparent);
}
.references a { color: var(--accent, #4f8cff); word-break: break-word; }
.references a:hover { text-decoration: underline; }

/* Each reference = a prominent title with the grayish citation beneath it.
   The citation links to the source (_blank) unless it's the MKSAP book (plain). */
.references .ref-title {
  display: block;
  font-family: var(--font-sans, sans-serif);
  font-weight: 700;
  font-size: var(--font-sm, .92rem);
  line-height: 1.4;
  color: var(--text-primary, #212529);
}
.references .ref-cite {
  display: block;
  font-size: var(--font-xs, .8rem);
  line-height: 1.55;
  color: var(--text-muted, #8a919a);
  text-decoration: none;
  word-break: break-word;
  margin-top: 1px;
}
.references a.ref-cite { color: var(--text-secondary, #6c757d); }
.references a.ref-cite:hover { color: var(--accent, #4f8cff); text-decoration: underline; }

/* In-text citation superscript, e.g. [3] */
.cite {
  display: inline-block;
  font-size: .68em;
  font-weight: 700;
  font-family: var(--font-sans, sans-serif);
  color: var(--accent, #4f8cff);
  text-decoration: none;
  vertical-align: super;
  line-height: 0;
  padding: 0 1px;
  cursor: pointer;
  transition: color .15s, transform .15s;
}
.cite:hover { color: var(--primary, #1a5276); transform: translateY(-1px); }