/* ===========================
   Theme Variables
   =========================== */

/* Private dark palette — single source of truth for dark mode colours.
   Both the manual-toggle selector and the system-preference media query
   reference these tokens, so a colour change only needs to happen once. */
:root {
  --_dark-bg:                  #0f1419;
  --_dark-card:                #131a21;
  --_dark-text:                #e8edf2;
  --_dark-muted:               #9aa7b2;
  --_dark-primary:             #5bb1ff;
  --_dark-primary-dark:        #4595d6;
  --_dark-accent:              #4cd07a;
  --_dark-danger:              #ff6b6b;
  --_dark-border:              #27323c;
  --_dark-shadow:              0 8px 24px rgba(0,0,0,0.35);
  --_dark-hover-bg:            rgba(255,255,255,0.06);
  --_dark-active-bg:           rgba(91,177,255,0.12);
  --_dark-correct-bg:          rgba(76,208,122,0.12);
  --_dark-correct-border:      rgba(76,208,122,0.35);
  --_dark-incorrect-bg:        rgba(255,107,107,0.12);
  --_dark-incorrect-border:    rgba(255,107,107,0.35);
  --_dark-btn-secondary:       #1b2330;
  --_dark-btn-secondary-hover: #222c3a;
}

/* ── Light theme (default) ── */
:root {
  --font: 'Inter', system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial,
    "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", sans-serif;

  --clr-bg:                  #f7f8fa;
  --clr-card:                #ffffff;
  --clr-text:                #2c3e50;
  --clr-muted:               #6b7785;

  --clr-primary:             #3498db;
  --clr-primary-dark:        #2980b9;
  --clr-accent:              #27ae60;
  --clr-danger:              #e74c3c;
  --clr-border:              #e6e9ee;

  /* Contextual colours — components reference these so dark mode just
     swaps the tokens rather than needing extra override rules.       */
  --clr-hover-bg:            #f5f7fa;
  --clr-active-bg:           #ecf6fe;
  --clr-correct-bg:          #eaf9f0;
  --clr-correct-border:      #bfe8cf;
  --clr-incorrect-bg:        #fdecea;
  --clr-incorrect-border:    #f5c2bc;
  --clr-btn-secondary:       #ecf0f1;
  --clr-btn-secondary-hover: #e5eaee;

  --radius:    14px;
  --radius-sm: 10px;
  --gap:       24px;
  --gap-sm:    12px;
  --gap-xs:    8px;
  --shadow:    0 8px 24px rgba(0,0,0,0.06);
}

/* ── Dark theme: manual toggle ── */
:root[data-theme="dark"] {
  --clr-bg:                  var(--_dark-bg);
  --clr-card:                var(--_dark-card);
  --clr-text:                var(--_dark-text);
  --clr-muted:               var(--_dark-muted);
  --clr-primary:             var(--_dark-primary);
  --clr-primary-dark:        var(--_dark-primary-dark);
  --clr-accent:              var(--_dark-accent);
  --clr-danger:              var(--_dark-danger);
  --clr-border:              var(--_dark-border);
  --shadow:                  var(--_dark-shadow);
  --clr-hover-bg:            var(--_dark-hover-bg);
  --clr-active-bg:           var(--_dark-active-bg);
  --clr-correct-bg:          var(--_dark-correct-bg);
  --clr-correct-border:      var(--_dark-correct-border);
  --clr-incorrect-bg:        var(--_dark-incorrect-bg);
  --clr-incorrect-border:    var(--_dark-incorrect-border);
  --clr-btn-secondary:       var(--_dark-btn-secondary);
  --clr-btn-secondary-hover: var(--_dark-btn-secondary-hover);
}

/* ── Dark theme: OS/system preference (no manual toggle set) ── */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --clr-bg:                  var(--_dark-bg);
    --clr-card:                var(--_dark-card);
    --clr-text:                var(--_dark-text);
    --clr-muted:               var(--_dark-muted);
    --clr-primary:             var(--_dark-primary);
    --clr-primary-dark:        var(--_dark-primary-dark);
    --clr-accent:              var(--_dark-accent);
    --clr-danger:              var(--_dark-danger);
    --clr-border:              var(--_dark-border);
    --shadow:                  var(--_dark-shadow);
    --clr-hover-bg:            var(--_dark-hover-bg);
    --clr-active-bg:           var(--_dark-active-bg);
    --clr-correct-bg:          var(--_dark-correct-bg);
    --clr-correct-border:      var(--_dark-correct-border);
    --clr-incorrect-bg:        var(--_dark-incorrect-bg);
    --clr-incorrect-border:    var(--_dark-incorrect-border);
    --clr-btn-secondary:       var(--_dark-btn-secondary);
    --clr-btn-secondary-hover: var(--_dark-btn-secondary-hover);
  }
}

/* ===========================
   Base Reset
   =========================== */
*, *::before, *::after { box-sizing: border-box; }

/* Suppress the blue tap-flash rectangle on mobile */
* { -webkit-tap-highlight-color: transparent; }

html, body {
  margin: 0; padding: 0;
  background: var(--clr-bg);
  color: var(--clr-text);
  font-family: var(--font);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Smooth colour transitions when theme is toggled */
body, .app-header, .category-selection, .question,
.result, .history, .pool-count, .btn {
  transition: background-color 0.35s ease, color 0.35s ease, border-color 0.35s ease;
}

/* iOS Safari applies system button styling without this reset */
button {
  -webkit-appearance: none;
  appearance: none;
  font-family: inherit;
  font-size: inherit;
  cursor: pointer;
  border: none;
}

/* Hide JS-controlled buttons before the script runs to prevent a flash
   of all buttons at page load. JS sets inline style.display once ready. */
#submitBtn,
#retryBtn,
#retakeWrongBtn,
#changeCatBtn,
#resetHistoryBtn,
#refreshBtn {
  display: none;
}

/* ===========================
   Header
   =========================== */
.app-header {
  position: sticky;
  top: 0;
  z-index: 200;
  background: var(--clr-card);
  border-bottom: 1px solid var(--clr-border);
  padding: 16px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.03);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 20px;
}

.app-header h1 {
  margin: 0;
  font-size: 20px;
  font-weight: 700;
  flex-grow: 1;
  text-align: center;
  cursor: pointer;
  transition: color 0.2s ease;
}

.app-header h1:hover { color: var(--clr-primary); }

.app-header .header-right {
  position: absolute;
  right: 16px;
}

/* Stack title + toggle vertically on narrow screens */
@media (max-width: 600px) {
  .app-header {
    flex-direction: column;
    align-items: center;
    gap: 8px;
  }
  .app-header .header-right { position: static; }
  .app-header h1 { flex-grow: 0; }
}

/* ===========================
   Layout
   =========================== */
.container {
  max-width: 1100px;
  margin: 20px auto;
  padding: 0 16px;
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: var(--gap);
}

@media (max-width: 960px) {
  .container { grid-template-columns: 1fr; }
}

/* ===========================
   Category Panel
   =========================== */
.category-selection {
  background: var(--clr-card);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius);
  padding: 16px;
  box-shadow: var(--shadow);
}

.category-selection h2 {
  margin: 0 0 var(--gap-sm) 0;
  font-size: 18px;
}

/* Toggle switches row */
.category-toggles {
  display: flex;
  flex-wrap: wrap;
  gap: 16px 20px;
  margin-bottom: var(--gap-sm);
}

.toggle {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  cursor: pointer;
  user-select: none;
  font-weight: 600;
}

.toggle input { display: none; }

.toggle .switch {
  position: relative;
  width: 52px; height: 28px;
  background: #cfd6dd;
  border-radius: 999px;
  transition: background 0.3s ease;
  box-shadow: inset 0 1px 2px rgba(0,0,0,0.08);
  flex-shrink: 0;
}

.toggle .switch::after {
  content: "";
  position: absolute;
  top: 3px; left: 3px;
  width: 22px; height: 22px;
  background: #fff;
  border-radius: 50%;
  transition: transform 0.3s ease;
  box-shadow: 0 2px 8px rgba(0,0,0,0.15);
}

.toggle input:checked + .switch         { background: var(--clr-primary); }
.toggle input:checked + .switch::after  { transform: translateX(24px); }
.toggle .label-text                     { font-size: 14px; }

/* Chapter icon cards */
.chapter-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
  gap: var(--gap-sm);
  margin-bottom: var(--gap-sm);
}

@media (max-width: 600px) {
  .chapter-list { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

.chapter-item {
  background: var(--clr-card);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-sm);
  padding: 12px 10px;
  text-align: center;
  cursor: pointer;
  transition: transform 0.15s ease, border-color 0.2s ease, background 0.2s ease;
  box-shadow: 0 2px 8px rgba(0,0,0,0.03);
}

.chapter-item .icon  { display: block; font-size: 22px; margin-bottom: 6px; }
.chapter-item .label { font-size: 13px; font-weight: 600; }

.chapter-item:hover {
  transform: translateY(-1px);
  background: var(--clr-hover-bg);
}

.chapter-item.active {
  background: var(--clr-active-bg);
  border-color: var(--clr-primary);
}

/* Subcategory checklist */
.subcategory-list {
  display: grid;
  gap: 8px;
  margin-bottom: var(--gap-sm);
}

.subcategory-list label {
  display: flex;
  align-items: center;
  gap: 10px;
  background: var(--clr-card);
  border: 1px solid var(--clr-border);
  border-radius: 10px;
  padding: 10px 12px;
  font-size: 14px;
  cursor: pointer;
  transition: background 0.2s ease;
}

.subcategory-list label:hover { background: var(--clr-hover-bg); }
.subcategory-list input[type="checkbox"] { transform: scale(1.2); }

/* Pool count (sticky inside the left panel, below the sticky header) */
.pool-count {
  position: sticky;
  top: 62px;
  background: var(--clr-card);
  border: 1px solid var(--clr-border);
  border-radius: 10px;
  padding: 10px 12px;
  font-weight: 700;
  z-index: 50;
  margin-bottom: var(--gap-sm);
}

@media (max-width: 600px) { .pool-count { top: 58px; } }

/* Category control buttons */
.category-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

/* ===========================
   Buttons
   =========================== */
.btn {
  display: inline-block;
  padding: 10px 18px;
  border: none;
  border-radius: 999px;
  font-size: 14px;
  font-weight: 700;
  cursor: pointer;
  text-decoration: none;
  transition: background-color 0.25s ease, transform 0.15s ease, box-shadow 0.2s ease;
  box-shadow: 0 4px 12px rgba(0,0,0,0.06);
}

.btn:active { transform: translateY(1px); }

.btn.primary         { background: var(--clr-primary);             color: #fff; }
.btn.primary:hover   { background: var(--clr-primary-dark); }

.btn.secondary       { background: var(--clr-btn-secondary);       color: var(--clr-text); }
.btn.secondary:hover { background: var(--clr-btn-secondary-hover); }

/* ===========================
   Progress Indicator
   =========================== */
.progress-indicator {
  font-size: 13px;
  font-weight: 600;
  color: var(--clr-muted);
  padding: 6px 10px;
  background: var(--clr-card);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-sm);
  margin-bottom: var(--gap-sm);
}

/* Hide the indicator element entirely when empty so it takes up no space */
.progress-indicator:empty { display: none; }

/* ===========================
   Quiz
   =========================== */
.quiz-grid {
  display: grid;
  gap: var(--gap-sm);
}

.question {
  background: var(--clr-card);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius);
  padding: 14px;
  box-shadow: var(--shadow);
}

.question > p {
  margin: 0 0 8px 0;
  font-weight: 700;
}

.question-image {
  display: block;
  max-width: 100%;
  height: auto;
  margin: 8px 0 12px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--clr-border);
}

.question label {
  display: flex;
  align-items: center;
  gap: 10px;
  border: 1px solid var(--clr-border);
  border-radius: 10px;
  padding: 8px 10px;
  margin: 6px 0;
  cursor: pointer;
  transition: background 0.2s ease, border-color 0.2s ease;
}

.question label:hover         { background: var(--clr-hover-bg); }
.question input[type="radio"] { transform: scale(1.1); }

/* Answer highlighting after submit or instant feedback.
   Uses contextual tokens so dark-mode colours are inherited automatically. */
.question label.correct {
  background:  var(--clr-correct-bg);
  border-color: var(--clr-correct-border);
  box-shadow:  inset 0 0 0 1px var(--clr-correct-border);
}

.question label.incorrect {
  background:  var(--clr-incorrect-bg);
  border-color: var(--clr-incorrect-border);
  box-shadow:  inset 0 0 0 1px var(--clr-incorrect-border);
}

/* Inline feedback message (instant feedback mode only) */
.question .feedback {
  margin-top: 6px;
  font-size: 13px;
  font-weight: 600;
  color: var(--clr-muted);
}

/* ===========================
   Controls Bar
   =========================== */

/* Desktop: simple flex row, sits in normal document flow */
.controls {
  margin-top: var(--gap-sm);
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

/* Mobile: fixed to the bottom so it stays reachable while
   scrolling through a long quiz. The glassy background is a
   progressive enhancement — browsers without backdrop-filter
   or color-mix fall back to the solid var(--clr-card).       */
@media (max-width: 600px) {
  /* Reserve space so the last question card isn't hidden under the bar */
  body { padding-bottom: 80px; }

  .controls {
    position: fixed;
    left: 0; right: 0; bottom: 0;
    z-index: 1000;
    padding: 12px 16px;
    gap: 10px;
    flex-wrap: wrap;
    border-top: 1px solid var(--clr-border);
    box-shadow: 0 -6px 16px rgba(0,0,0,0.28);
    /* Solid fallback */
    background: var(--clr-card);
    /* Glass upgrade where supported */
    background: color-mix(in oklab, var(--clr-card) 85%, transparent);
    -webkit-backdrop-filter: blur(10px);
    backdrop-filter: blur(10px);
  }

  .controls .btn {
    flex: 1 1 auto;
    text-align: center;
  }
}

/* ===========================
   Result
   =========================== */
.result {
  margin-top: var(--gap-sm);
  font-weight: 700;
  background: var(--clr-card);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius);
  padding: 12px;
  box-shadow: var(--shadow);
}

/* Hide the card shell when there is no result text yet */
.result:empty { display: none; }

/* ===========================
   History
   =========================== */
.history {
  margin-top: var(--gap);
  background: var(--clr-card);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius);
  padding: 16px;
  box-shadow: var(--shadow);
}

.history h2  { margin: 0 0 8px 0; font-size: 18px; }
.best-score  { font-weight: 700; margin-bottom: 8px; }

.history-list    { list-style: none; margin: 0; padding: 0; }
.history-list li {
  padding: 8px 0;
  border-bottom: 1px dashed var(--clr-border);
  font-size: 14px;
}
.history-list li:last-child { border-bottom: none; }

/* ===========================
   History — score trend arrows
   =========================== */
.trend-up   { color: var(--clr-accent); font-weight: 700; }
.trend-down { color: var(--clr-danger); font-weight: 700; }
.trend-flat { color: var(--clr-muted);  font-weight: 700; }

/* .quiz-header rules moved to end of file (two-row layout with mode label) */

/* ===========================
   Timer
   =========================== */
.timer {
  font-size: 14px;
  font-weight: 700;
  color: var(--clr-primary);
  padding: 6px 14px;
  background: var(--clr-card);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-sm);
  white-space: nowrap;
}

/* Don't occupy space when the timer isn't running */
.timer:empty { display: none; }

/* Escalating colour as time runs low */
.timer--warning {
  color: #c87d00;
  border-color: #f0c060;
  background: #fffbef;
}

.timer--critical {
  color: var(--clr-danger);
  border-color: var(--clr-incorrect-border);
  background: var(--clr-incorrect-bg);
  animation: timer-pulse 1s ease-in-out infinite;
}

@keyframes timer-pulse {
  0%, 100% { opacity: 1; }
  50%       { opacity: 0.55; }
}

/* Dark mode overrides for the hard-coded warning colours */
:root[data-theme="dark"] .timer--warning {
  color: #f0c060;
  border-color: #7a5c00;
  background: rgba(240, 192, 96, 0.1);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) .timer--warning {
    color: #f0c060;
    border-color: #7a5c00;
    background: rgba(240, 192, 96, 0.1);
  }
}

/* ===========================
   Chapter cards — question count badge
   =========================== */
.chapter-item .badge {
  display: block;
  font-size: 11px;
  font-weight: 700;
  color: var(--clr-muted);
  margin-top: 4px;
}

/* ===========================
   Unanswered question highlight
   =========================== */
.question.unanswered {
  border-color: var(--clr-danger);
  /* Layer the alert ring on top of the existing shadow */
  box-shadow: var(--shadow), 0 0 0 2px var(--clr-incorrect-border);
}

/* ===========================
   Result banner — pass / fail colour
   =========================== */
.result--pass {
  color: var(--clr-accent);
  background: var(--clr-correct-bg);
  border-color: var(--clr-correct-border);
}

.result--fail {
  color: var(--clr-danger);
  background: var(--clr-incorrect-bg);
  border-color: var(--clr-incorrect-border);
}

/* ===========================
   Per-chapter score breakdown
   =========================== */
.result-breakdown {
  margin-top: var(--gap-sm);
  background: var(--clr-card);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius);
  padding: 12px;
  box-shadow: var(--shadow);
}

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

.breakdown-heading {
  margin: 0 0 8px 0;
  font-size: 12px;
  font-weight: 700;
  color: var(--clr-muted);
  text-transform: uppercase;
  letter-spacing: 0.6px;
}

.breakdown-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 6px 10px;
  border-radius: 8px;
  margin-bottom: 4px;
  font-size: 14px;
}

.breakdown-row:last-child { margin-bottom: 0; }

.breakdown-pass { background: var(--clr-correct-bg);   color: var(--clr-accent); }
.breakdown-fail { background: var(--clr-incorrect-bg); color: var(--clr-danger); }

.breakdown-chapter { font-weight: 600; }
.breakdown-score   { font-weight: 700; }

/* ===========================
   Mode Tabs
   =========================== */
.mode-tabs {
  display: flex;
  gap: 4px;
  background: var(--clr-bg);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-sm);
  padding: 4px;
  margin-bottom: 14px;
}

.mode-tab {
  flex: 1;
  padding: 8px 4px;
  border: none;
  border-radius: 8px;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  background: transparent;
  color: var(--clr-muted);
  font-family: inherit;
  transition: background 0.2s ease, color 0.2s ease;
}

.mode-tab.active {
  background: var(--clr-card);
  color: var(--clr-primary);
  box-shadow: 0 1px 4px rgba(0,0,0,0.08);
}

.mode-tab:hover:not(.active) {
  background: var(--clr-hover-bg);
  color: var(--clr-text);
}

/* ===========================
   Mode hint text
   =========================== */
.mode-hint {
  font-size: 13px;
  color: var(--clr-muted);
  margin: 0 0 10px 0;
  line-height: 1.5;
}

/* ===========================
   Section Cards (Module Quiz)
   =========================== */
.section-cards {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.section-card {
  display: flex;
  align-items: center;
  gap: 12px;
  background: var(--clr-card);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-sm);
  padding: 12px;
  transition: background 0.2s ease, transform 0.15s ease, border-color 0.2s ease;
}

.section-card:hover {
  background: var(--clr-hover-bg);
  transform: translateY(-1px);
}

.section-info { flex: 1; min-width: 0; }

.section-name {
  font-weight: 600;
  font-size: 14px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.section-count {
  font-size: 12px;
  color: var(--clr-muted);
  margin-top: 2px;
}

.section-start-btn {
  flex-shrink: 0;
  padding: 8px 14px;
  font-size: 13px;
}

/* ===========================
   Final Exam panel
   =========================== */
.final-exam-stats {
  margin-top: 10px;
  background: var(--clr-bg);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-sm);
  overflow: hidden;
}

.final-stat-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 6px 10px;
  border-bottom: 1px solid var(--clr-border);
  gap: 8px;
}

.final-stat-row:last-child { border-bottom: none; }

.fsr-name {
  font-size: 12px;
  font-weight: 600;
  flex: 1;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.fsr-count {
  font-size: 11px;
  color: var(--clr-muted);
  flex-shrink: 0;
}

.btn.full-width {
  width: 100%;
  text-align: center;
  display: block;
  box-sizing: border-box;
  margin-top: 10px;
}

/* ===========================
   Shared toggles
   =========================== */
.shared-toggles {
  display: flex;
  flex-wrap: wrap;
  gap: 12px 16px;
  margin-top: 14px;
  padding-top: 14px;
  border-top: 1px solid var(--clr-border);
}

/* ===========================
   Quiz mode label
   =========================== */
.quiz-mode-label {
  font-size: 11px;
  font-weight: 700;
  color: var(--clr-primary);
  text-transform: uppercase;
  letter-spacing: 0.6px;
  margin-bottom: 6px;
}

.quiz-mode-label:empty { display: none; }

/* Quiz header: two-row layout (label above, progress+timer below) */
.quiz-header {
  display: none;
  flex-direction: column;
  gap: 0;
  margin-bottom: var(--gap-sm);
}

.quiz-header-row {
  display: flex;
  align-items: stretch;
  gap: var(--gap-sm);
}

/* Inside the row the indicator fills remaining space */
.quiz-header-row .progress-indicator {
  flex: 1;
  margin-bottom: 0;
}

/* ===========================
   Footer
   =========================== */
.app-footer {
  text-align: center;
  padding: 16px;
  font-size: 11px;
  color: var(--clr-muted);
  opacity: 0.6;
  letter-spacing: 0.3px;
}