/* ===========================================
   CSS for Python Concurrency Quiz
   =========================================== */

/* -------------------------------------------
   Minimal Reset
   
   Gets us to a consistent starting point
   across all browsers.
   ------------------------------------------- */

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

body {
  margin: 0;
}

button {
  font: inherit;
}

/* Focus states for accessibility */
button:focus-visible,
a:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* -------------------------------------------
   CSS Custom Properties (Variables)
   
   Light mode is the default.
   Dark mode overrides via media query below.
   ------------------------------------------- */

:root {
  /* Base colors */
  --color-bg: #ffffff;
  --color-bg-secondary: #f5f5f5;
  --color-text: #1a1a1a;
  --color-text-muted: #666666;

  /* Interactive elements */
  --color-primary: #0066cc;
  --color-primary-hover: #0052a3;

  /* Feedback colors */
  --color-correct: #2e7d32;

  /* Borders */
  --color-border: #dddddd;

  /* Spacing scale */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;

  /* Typography */
  --font-sans: system-ui, -apple-system, sans-serif;
  --font-mono: ui-monospace, "Cascadia Code", "Consolas", monospace;
  --font-size-base: 1.0625rem;
  --line-height: 1.5;
}

/* Dark mode overrides */
@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #1a1a1a;
    --color-bg-secondary: #2d2d2d;
    --color-text: #e0e0e0;
    --color-text-muted: #a0a0a0;

    --color-primary: #4da6ff;
    --color-primary-hover: #80bfff;

    --color-correct: #66bb6a;

    --color-border: #444444;
  }
}

/* -------------------------------------------
   Base Styles
   
   Apply variables to fundamental elements.
   ------------------------------------------- */

body {
  font-family: var(--font-sans);
  font-size: var(--font-size-base);
  line-height: var(--line-height);
  color: var(--color-text);
  background-color: var(--color-bg);
}

/* Ensure hidden attribute works even with display overrides */
[hidden] {
  display: none !important;
}

/* -------------------------------------------
   Splash Screen
   ------------------------------------------- */

#splash-screen {
  /* Center content vertically and horizontally */
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: var(--space-lg);
  text-align: center;
}

/* Splash screen fade-in animation */
@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

#splash-screen h1,
#splash-screen p,
#splash-screen button,
#splash-screen footer {
  opacity: 0;
  animation: fadeIn 1.25s ease forwards;
}

#splash-screen h1 {
  margin: 0 0 var(--space-md) 0;
  font-size: 2.125rem;
  animation-delay: 1s;
}

#splash-screen p:first-of-type {
  font-size: 1.5rem;
  animation-delay: 3s;
}

#splash-screen p:nth-of-type(2),
#splash-screen button,
#splash-screen footer {
  animation-delay: 5s;
}

#splash-screen p {
  margin: 0 0 var(--space-md) 0;
}

#splash-screen p.muted {
  color: var(--color-text-muted);
}

#splash-screen a {
  color: var(--color-primary);
}

#splash-screen a:hover {
  color: var(--color-primary-hover);
}

#start-quiz-button {
  margin-top: var(--space-md);
  padding: var(--space-sm) var(--space-lg);
  font-size: var(--font-size-base);
  color: #ffffff;
  background-color: var(--color-primary);
  border: none;
  border-radius: 4px;
  cursor: pointer;
}

#start-quiz-button:hover {
  background-color: var(--color-primary-hover);
}

#splash-screen footer {
  position: absolute;
  bottom: var(--space-lg);
  color: var(--color-text-muted);
  font-size: 0.9375rem;
}

#splash-screen footer a {
  color: var(--color-text-muted);
}

#splash-screen footer a:hover {
  color: var(--color-primary);
}

/* -------------------------------------------
   Navigation Bar
   ------------------------------------------- */

#nav-bar {
  display: flex;
  flex-wrap: nowrap;
  gap: 0.125rem;
  justify-content: center;
  max-width: 46rem;
  margin: 0 auto var(--space-md);
  padding: var(--space-lg) var(--space-lg) 0;
  overflow-x: auto;
}

#nav-bar button {
  width: 1.75rem;
  height: 1.75rem;
  min-width: 1.75rem;
  padding: 0;
  border: 2px solid var(--color-border);
  border-radius: 4px;
  background-color: var(--color-bg);
  color: var(--color-text);
  cursor: pointer;
  font-size: 0.75rem;
  transition:
    background-color 0.1s,
    border-color 0.1s,
    color 0.1s;
}

/* Disabled: future questions user hasn't reached yet */
#nav-bar button:disabled {
  opacity: 0.3;
  background-color: var(--color-bg-secondary);
  cursor: not-allowed;
}

/* Currently viewing this question - bold border */
#nav-bar button.viewing {
  border-width: 3px;
  border-color: var(--color-text);
}

/* Previously answered correctly */
#nav-bar button.correct {
  border-color: var(--color-correct);
  background-color: var(--color-correct);
  color: #ffffff;
}

/* Viewing + correct: keep green, add bold border */
#nav-bar button.viewing.correct {
  border-color: var(--color-text);
}

/* Mobile: allow nav buttons to wrap instead of scroll */
@media (max-width: 480px) {
  #nav-bar {
    flex-wrap: wrap;
    overflow-x: visible;
  }
}

/* -------------------------------------------
   Main Content Layout
   ------------------------------------------- */

#main-content {
  position: relative;
  max-width: 44rem;
  margin: 0 auto;
  padding: 0.75rem var(--space-lg) var(--space-lg);
}

/* Preface text (question prompt) */
#preface-text {
  margin-bottom: var(--space-md);
}

#preface-text p {
  margin: 0;
}

/* -------------------------------------------
   Code Display
   ------------------------------------------- */

#code-row {
  position: relative;
}

#code-row > pre {
  /* Fixed height so answers stay in same position */
  /* height = (lines × font-size × line-height) + (padding × 2) + buffer */
  height: calc(var(--max-snippet-lines) * 0.9375rem * 1.6 + 2rem + 0.25rem);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  overflow-y: auto;
  background: #fff;
}

@media (prefers-color-scheme: dark) {
  #code-row > pre {
    background: #0d1117;
  }
}

#code-display {
  display: block;
  width: 100%;
  padding: var(--space-md);
  font-family: var(--font-mono);
  font-size: 0.9375rem;
  line-height: 1.6;
  overflow-x: auto;
}

pre {
  margin: 0;
}

/* -------------------------------------------
   Answer Buttons
   ------------------------------------------- */

/* Container for answer buttons and next button */
#answers-row {
  display: flex;
  flex-direction: row;
  gap: var(--space-sm);
  margin: var(--space-lg) 0;
}

/* Base answer button styles */
#answer-0,
#answer-1,
#answer-2 {
  flex: 1;
  /* Allow flex items to shrink below content size */
  min-width: 0;
  /* Fixed height based on max answer lines */
  height: calc(var(--max-answer-lines) * 0.9375rem * 1.6 + var(--space-sm) * 2);
  padding: var(--space-sm) var(--space-md);
  border: 2px solid var(--color-border);
  border-radius: 4px;
  background-color: var(--color-bg);
  color: var(--color-text);
  text-align: left;
  cursor: pointer;
  transition:
    background-color 0.1s,
    border-color 0.1s,
    color 0.1s;
  /* Top-align content */
  display: flex;
  align-items: flex-start;
}

/* Wrapper for answer text - enables horizontal scroll at button bottom */
.answer-content {
  width: 100%;
  height: 100%;
  overflow-x: auto;
}

#answer-0:hover:not(:disabled),
#answer-1:hover:not(:disabled),
#answer-2:hover:not(:disabled) {
  border-color: var(--color-primary);
}

#answer-0:disabled,
#answer-1:disabled,
#answer-2:disabled {
  cursor: default;
}

/* Answer button text (preserve whitespace for output formatting) */
#answer-0 pre,
#answer-1 pre,
#answer-2 pre {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 0.9375rem;
  white-space: pre;
}

/* Selected answer (the one user clicked) - bold border */
#answer-0.selected,
#answer-1.selected,
#answer-2.selected {
  border-width: 3px;
  border-color: var(--color-text);
}

/* Correct answer - green */
#answer-0.correct,
#answer-1.correct,
#answer-2.correct {
  border-color: var(--color-correct);
  background-color: var(--color-correct);
  color: #ffffff;
}

/* Selected + correct: green background, bold border */
#answer-0.selected.correct,
#answer-1.selected.correct,
#answer-2.selected.correct {
  border-color: var(--color-text);
}

/* -------------------------------------------
   Explanation Section
   ------------------------------------------- */

#explanation-section {
  margin: var(--space-lg) 0;
}

#explanation-text {
  line-height: var(--line-height);
}

#explanation-text p {
  margin: 0 0 var(--space-sm) 0;
}

#explanation-text p:last-child {
  margin-bottom: 0;
}

#explanation-text code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background-color: var(--color-bg);
  padding: 0.1em 0.3em;
  border-radius: 3px;
}

/* -------------------------------------------
   Action Buttons (Next, Finish, Restart)
   ------------------------------------------- */

/* Nav buttons container - below explanation on mobile, beside code on desktop */
#nav-buttons {
  display: flex;
  gap: var(--space-sm);
  margin-top: var(--space-md);
}

#next-button,
#finish-button {
  flex: 1;
  height: 2.5rem;
  padding: 0;
  font-size: 1.5rem;
  color: var(--color-text-muted);
  background-color: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  cursor: pointer;
}

#next-button:hover,
#finish-button:hover {
  color: var(--color-text);
  border-color: var(--color-text);
}

/* Desktop: position nav buttons beside code block */
@media (min-width: 481px) {
  #nav-buttons {
    position: absolute;
    /* top = padding + preface line height + preface margin */
    top: calc(
      0.75rem + var(--font-size-base) * var(--line-height) + var(--space-md)
    );
    right: calc(-1 * (var(--space-md) + 2.5rem));
    flex-direction: column;
    width: 2.5rem;
    height: calc(var(--max-snippet-lines) * 0.9375rem * 1.6 + 2rem + 0.25rem);
    margin-top: 0;
  }

  #next-button,
  #finish-button {
    flex: 1;
    width: 2.5rem;
  }
}

#restart-button {
  margin-top: var(--space-md);
  padding: var(--space-sm) var(--space-lg);
  font-size: var(--font-size-base);
  color: #ffffff;
  background-color: var(--color-primary);
  border: none;
  border-radius: 4px;
  cursor: pointer;
}

#restart-button:hover {
  background-color: var(--color-primary-hover);
}

/* -------------------------------------------
   Final Score Section
   ------------------------------------------- */

#final-score-section {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: var(--space-lg);
  text-align: center;
}

#final-score-section p {
  margin: 0 0 var(--space-md) 0;
  font-size: 4rem;
  font-weight: bold;
}

#final-score-section a {
  color: var(--color-primary);
}

#final-score-section a:hover {
  color: var(--color-primary-hover);
}

#final-score-section p.anki-plug {
  margin-top: var(--space-lg);
  font-size: 1rem;
  color: var(--color-text-muted);
}

/* -------------------------------------------
   Continue Dialog
   ------------------------------------------- */

#continue-dialog {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: var(--space-lg);
}

#continue-dialog > div {
  max-width: 24rem;
  padding: var(--space-lg);
  background-color: var(--color-bg-secondary);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  text-align: center;
}

#continue-dialog h3 {
  margin: 0 0 var(--space-md) 0;
}

#continue-dialog p {
  margin: 0 0 var(--space-sm) 0;
}

#continue-dialog button {
  margin: var(--space-md) var(--space-xs) 0;
  padding: var(--space-sm) var(--space-md);
  font-size: var(--font-size-base);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  cursor: pointer;
}

#continue-from-saved-button {
  color: #ffffff;
  background-color: var(--color-primary);
  border-color: var(--color-primary);
}

#continue-from-saved-button:hover {
  background-color: var(--color-primary-hover);
  border-color: var(--color-primary-hover);
}

#restart-from-saved-button {
  color: var(--color-text);
  background-color: var(--color-bg);
}

#restart-from-saved-button:hover {
  background-color: var(--color-bg-secondary);
}