/* ===========================
   Reset & Base
   =========================== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --blue-50:  #eff6ff;
  --blue-100: #dbeafe;
  --blue-200: #bfdbfe;
  --blue-400: #60a5fa;
  --blue-500: #3b82f6;
  --blue-600: #2563eb;
  --blue-700: #1d4ed8;
  --blue-800: #1e40af;
  --blue-900: #1e3a8a;

  --green-50:  #f0fdf4;
  --green-400: #4ade80;
  --green-500: #22c55e;
  --green-600: #16a34a;

  --red-50:  #fef2f2;
  --red-400: #f87171;
  --red-500: #ef4444;
  --red-600: #dc2626;

  --gray-50:  #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-500: #6b7280;
  --gray-700: #374151;
  --gray-900: #111827;

  --shadow-sm: 0 1px 2px rgba(0,0,0,.06);
  --shadow:    0 4px 16px rgba(37,99,235,.12);
  --shadow-lg: 0 8px 32px rgba(37,99,235,.18);

  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-xl: 24px;

  --transition: .2s cubic-bezier(.4,0,.2,1);
}

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: 'Hiragino Sans', 'Hiragino Kaku Gothic ProN', 'Noto Sans JP',
               'Meiryo', sans-serif;
  background: linear-gradient(135deg, #e0f0ff 0%, #f0f7ff 40%, #e8f0ff 100%);
  min-height: 100vh;
  color: var(--gray-900);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* ===========================
   App Shell
   =========================== */
#app {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.screen {
  display: none;
  flex: 1;
  flex-direction: column;
  animation: fadeIn .35s ease;
}

.screen.active {
  display: flex;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(16px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ===========================
   Header
   =========================== */
.app-header {
  background: linear-gradient(135deg, var(--blue-700) 0%, var(--blue-500) 100%);
  padding: 1.25rem 1.5rem 1rem;
  display: flex;
  align-items: center;
  gap: .75rem;
  box-shadow: 0 4px 20px rgba(37,99,235,.35);
}

.app-header .logo {
  font-size: 1.6rem;
  line-height: 1;
}

.app-header h1 {
  font-size: 1.05rem;
  font-weight: 700;
  color: #fff;
  letter-spacing: .02em;
  line-height: 1.25;
}

.app-header h1 small {
  display: block;
  font-size: .7rem;
  font-weight: 400;
  color: var(--blue-200);
  letter-spacing: .04em;
  margin-top: .1rem;
}

/* ===========================
   Top Screen
   =========================== */
.top-content {
  padding: 1.5rem 1.25rem 2rem;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  max-width: 540px;
  margin: 0 auto;
  width: 100%;
}

.welcome-banner {
  background: linear-gradient(135deg, var(--blue-600), var(--blue-400));
  border-radius: var(--radius-xl);
  padding: 1.5rem 1.5rem 1.25rem;
  color: #fff;
  text-align: center;
  box-shadow: var(--shadow-lg);
}

.welcome-banner .banner-icon {
  font-size: 3rem;
  display: block;
  margin-bottom: .5rem;
}

.welcome-banner h2 {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: .35rem;
}

.welcome-banner p {
  font-size: .85rem;
  opacity: .9;
  line-height: 1.5;
}

/* Overall progress */
.overall-progress {
  background: #fff;
  border-radius: var(--radius-lg);
  padding: 1rem 1.25rem;
  box-shadow: var(--shadow);
}

.overall-progress h3 {
  font-size: .85rem;
  font-weight: 600;
  color: var(--gray-700);
  margin-bottom: .6rem;
}

.overall-bar-wrap {
  background: var(--gray-200);
  border-radius: 99px;
  height: 10px;
  overflow: hidden;
  margin-bottom: .4rem;
}

.overall-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--blue-500), var(--blue-400));
  border-radius: 99px;
  transition: width .6s cubic-bezier(.4,0,.2,1);
}

.overall-label {
  font-size: .78rem;
  color: var(--gray-500);
  text-align: right;
}

/* Chapter cards */
.chapters-title {
  font-size: .9rem;
  font-weight: 700;
  color: var(--blue-800);
  letter-spacing: .04em;
  text-transform: uppercase;
}

.chapter-list {
  display: flex;
  flex-direction: column;
  gap: .9rem;
}

.chapter-card {
  background: #fff;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  overflow: hidden;
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition);
  border: 2px solid transparent;
  position: relative;
}

.chapter-card:hover,
.chapter-card:focus {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  border-color: var(--blue-300, #93c5fd);
  outline: none;
}

.chapter-card:active {
  transform: translateY(0) scale(.98);
}

.chapter-card-inner {
  padding: 1.1rem 1.25rem;
  display: flex;
  align-items: flex-start;
  gap: 1rem;
}

.chapter-icon {
  font-size: 2rem;
  flex-shrink: 0;
  line-height: 1;
  margin-top: .1rem;
}

.chapter-info {
  flex: 1;
}

.chapter-title {
  font-size: .95rem;
  font-weight: 700;
  color: var(--blue-800);
  margin-bottom: .3rem;
}

.chapter-subtitle {
  font-size: .75rem;
  color: var(--gray-500);
  margin-bottom: .65rem;
}

.chapter-progress {
  display: flex;
  align-items: center;
  gap: .6rem;
}

.progress-bar-wrap {
  flex: 1;
  background: var(--gray-200);
  border-radius: 99px;
  height: 7px;
  overflow: hidden;
}

.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--blue-500), var(--blue-400));
  border-radius: 99px;
  transition: width .6s cubic-bezier(.4,0,.2,1);
}

.progress-label {
  font-size: .7rem;
  font-weight: 600;
  color: var(--blue-600);
  white-space: nowrap;
}

.chapter-badge {
  display: inline-flex;
  align-items: center;
  gap: .25rem;
  background: var(--blue-50);
  color: var(--blue-700);
  font-size: .7rem;
  font-weight: 600;
  padding: .2rem .55rem;
  border-radius: 99px;
  border: 1px solid var(--blue-200);
  margin-top: .5rem;
}

.chapter-badge.perfect {
  background: #f0fdf4;
  color: var(--green-600);
  border-color: #bbf7d0;
}

.chapter-arrow {
  font-size: 1.2rem;
  color: var(--blue-300, #93c5fd);
  align-self: center;
  flex-shrink: 0;
}

/* ===========================
   Quiz Screen
   =========================== */
.quiz-header {
  background: linear-gradient(135deg, var(--blue-700) 0%, var(--blue-500) 100%);
  padding: 1rem 1.25rem .85rem;
  display: flex;
  align-items: center;
  gap: .75rem;
  box-shadow: 0 4px 20px rgba(37,99,235,.3);
}

.btn-back {
  background: rgba(255,255,255,.18);
  border: none;
  color: #fff;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  font-size: 1.1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background var(--transition), transform var(--transition);
  flex-shrink: 0;
}

.btn-back:hover { background: rgba(255,255,255,.3); }
.btn-back:active { transform: scale(.9); }

.quiz-header-info {
  flex: 1;
}

.quiz-chapter-name {
  font-size: .72rem;
  color: var(--blue-200);
  font-weight: 500;
  letter-spacing: .04em;
}

.quiz-counter {
  font-size: .85rem;
  font-weight: 700;
  color: #fff;
}

/* Progress bar */
.quiz-progress-wrap {
  padding: .75rem 1.25rem .5rem;
  background: #fff;
}

.progress-track {
  background: var(--gray-200);
  border-radius: 99px;
  height: 10px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--blue-600), var(--blue-400));
  border-radius: 99px;
  transition: width .5s cubic-bezier(.4,0,.2,1);
}

/* Quiz body */
.quiz-body {
  flex: 1;
  overflow-y: auto;
  padding: 1rem 1.25rem 1.5rem;
  max-width: 540px;
  margin: 0 auto;
  width: 100%;
}

.question-card {
  background: #fff;
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow);
  padding: 1.4rem 1.25rem 1.5rem;
  margin-bottom: 1.25rem;
  transition: box-shadow var(--transition);
}

.question-section {
  display: inline-block;
  background: var(--blue-50);
  color: var(--blue-700);
  font-size: .7rem;
  font-weight: 700;
  padding: .2rem .6rem;
  border-radius: 99px;
  border: 1px solid var(--blue-200);
  margin-bottom: .8rem;
  letter-spacing: .03em;
}

.question-text {
  font-size: 1rem;
  font-weight: 600;
  line-height: 1.65;
  color: var(--gray-900);
}

/* Choices */
.choices-list {
  display: flex;
  flex-direction: column;
  gap: .65rem;
}

.choice-btn {
  width: 100%;
  background: #fff;
  border: 2px solid var(--gray-200);
  border-radius: var(--radius-md);
  padding: .85rem 1rem .85rem 1rem;
  display: flex;
  align-items: flex-start;
  gap: .8rem;
  cursor: pointer;
  text-align: left;
  font-size: .92rem;
  color: var(--gray-900);
  line-height: 1.5;
  transition: border-color var(--transition), background var(--transition),
              transform var(--transition), box-shadow var(--transition);
  position: relative;
  overflow: hidden;
  font-family: inherit;
}

.choice-btn:hover:not(:disabled) {
  border-color: var(--blue-400);
  background: var(--blue-50);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(37,99,235,.15);
}

.choice-btn:active:not(:disabled) {
  transform: translateY(0) scale(.98);
}

.choice-label {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: var(--gray-100);
  color: var(--gray-700);
  font-size: .78rem;
  font-weight: 700;
  flex-shrink: 0;
  margin-top: .05rem;
  transition: background var(--transition), color var(--transition);
}

.choice-text {
  flex: 1;
}

/* Correct / Incorrect states */
.choice-btn.correct {
  border-color: var(--green-500);
  background: var(--green-50);
  animation: pulse-correct .4s ease;
}

.choice-btn.correct .choice-label {
  background: var(--green-500);
  color: #fff;
}

.choice-btn.incorrect {
  border-color: var(--red-500);
  background: var(--red-50);
  animation: shake .35s ease;
}

.choice-btn.incorrect .choice-label {
  background: var(--red-500);
  color: #fff;
}

.choice-btn:disabled {
  cursor: default;
  opacity: .85;
}

@keyframes pulse-correct {
  0%   { transform: scale(1); }
  40%  { transform: scale(1.03); }
  100% { transform: scale(1); }
}

@keyframes shake {
  0%,100% { transform: translateX(0); }
  20%     { transform: translateX(-6px); }
  40%     { transform: translateX(6px); }
  60%     { transform: translateX(-4px); }
  80%     { transform: translateX(4px); }
}

/* Ripple */
.ripple {
  position: absolute;
  border-radius: 50%;
  transform: scale(0);
  animation: ripple-anim .5s linear;
  pointer-events: none;
  background: rgba(37,99,235,.18);
}

@keyframes ripple-anim {
  to { transform: scale(4); opacity: 0; }
}

/* ===========================
   Feedback Panel
   =========================== */
.feedback-panel {
  background: #fff;
  border-radius: var(--radius-xl) var(--radius-xl) 0 0;
  padding: 1.25rem 1.25rem 1.5rem;
  box-shadow: 0 -4px 24px rgba(0,0,0,.08);
  transform: translateY(100%);
  transition: transform .35s cubic-bezier(.4,0,.2,1);
  position: sticky;
  bottom: 0;
}

.feedback-panel.show {
  transform: translateY(0);
}

.feedback-panel.correct-fb {
  border-top: 4px solid var(--green-500);
}

.feedback-panel.incorrect-fb {
  border-top: 4px solid var(--red-500);
}

.feedback-header {
  display: flex;
  align-items: center;
  gap: .6rem;
  margin-bottom: .5rem;
}

.feedback-icon {
  font-size: 1.6rem;
  line-height: 1;
}

.feedback-title {
  font-size: 1rem;
  font-weight: 700;
}

.correct-fb .feedback-title { color: var(--green-600); }
.incorrect-fb .feedback-title { color: var(--red-600); }

.feedback-correct-ans {
  font-size: .82rem;
  color: var(--gray-700);
  margin-bottom: .5rem;
  font-weight: 500;
}

.feedback-explanation {
  font-size: .85rem;
  color: var(--gray-700);
  line-height: 1.6;
  margin-bottom: 1rem;
}

.btn-next {
  width: 100%;
  background: linear-gradient(135deg, var(--blue-600), var(--blue-500));
  color: #fff;
  border: none;
  border-radius: var(--radius-md);
  padding: .9rem;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  letter-spacing: .03em;
  transition: transform var(--transition), box-shadow var(--transition),
              filter var(--transition);
  font-family: inherit;
}

.btn-next:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(37,99,235,.35);
  filter: brightness(1.05);
}

.btn-next:active {
  transform: translateY(0) scale(.97);
}

/* ===========================
   Result Screen
   =========================== */
#result-screen {
  background: linear-gradient(160deg, var(--blue-900) 0%, var(--blue-700) 60%, var(--blue-500) 100%);
}

.result-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 2rem 1.5rem;
  gap: 1.5rem;
  max-width: 480px;
  margin: 0 auto;
  width: 100%;
  text-align: center;
}

.result-trophy {
  font-size: 5rem;
  line-height: 1;
  filter: drop-shadow(0 0 20px rgba(255,215,0,.5));
  animation: trophy-bounce .6s cubic-bezier(.34,1.56,.64,1) .2s both;
}

@keyframes trophy-bounce {
  from { transform: scale(0) rotate(-15deg); opacity: 0; }
  to   { transform: scale(1) rotate(0deg); opacity: 1; }
}

.result-title {
  font-size: 1.8rem;
  font-weight: 800;
  color: #fff;
  letter-spacing: .02em;
  text-shadow: 0 2px 8px rgba(0,0,0,.3);
}

.result-chapter-name {
  font-size: .9rem;
  color: var(--blue-200);
  margin-top: -.5rem;
}

.result-score-card {
  background: rgba(255,255,255,.12);
  backdrop-filter: blur(8px);
  border: 1px solid rgba(255,255,255,.2);
  border-radius: var(--radius-xl);
  padding: 1.5rem 2rem;
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: .5rem;
}

.result-score {
  font-size: 3.5rem;
  font-weight: 800;
  color: #fff;
  line-height: 1;
}

.result-score span {
  font-size: 1.2rem;
  font-weight: 400;
  opacity: .8;
}

.result-correct-count {
  font-size: .95rem;
  color: var(--blue-100);
}

.result-accuracy-bar-wrap {
  width: 100%;
  background: rgba(255,255,255,.2);
  border-radius: 99px;
  height: 12px;
  overflow: hidden;
  margin-top: .5rem;
}

.result-accuracy-bar {
  height: 100%;
  border-radius: 99px;
  background: linear-gradient(90deg, #4ade80, #22c55e);
  transition: width 1s cubic-bezier(.4,0,.2,1) .5s;
}

.result-msg {
  font-size: 1rem;
  color: #fff;
  font-weight: 600;
  line-height: 1.5;
}

.result-actions {
  display: flex;
  flex-direction: column;
  gap: .75rem;
  width: 100%;
}

.btn-retry {
  background: #fff;
  color: var(--blue-700);
  border: none;
  border-radius: var(--radius-md);
  padding: .95rem;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  font-family: inherit;
  transition: transform var(--transition), box-shadow var(--transition);
  letter-spacing: .02em;
}

.btn-retry:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(0,0,0,.2);
}

.btn-retry:active { transform: translateY(0) scale(.97); }

.btn-top {
  background: transparent;
  color: rgba(255,255,255,.85);
  border: 2px solid rgba(255,255,255,.4);
  border-radius: var(--radius-md);
  padding: .85rem;
  font-size: .95rem;
  font-weight: 600;
  cursor: pointer;
  font-family: inherit;
  transition: background var(--transition), border-color var(--transition),
              transform var(--transition);
}

.btn-top:hover {
  background: rgba(255,255,255,.1);
  border-color: rgba(255,255,255,.7);
  transform: translateY(-2px);
}

.btn-top:active { transform: translateY(0) scale(.97); }

/* Stars animation on result */
.stars-container {
  position: fixed;
  inset: 0;
  pointer-events: none;
  overflow: hidden;
  z-index: 100;
}

.star-particle {
  position: absolute;
  font-size: 1.2rem;
  animation: star-fall 1.5s ease-out forwards;
  opacity: 0;
}

@keyframes star-fall {
  0%   { opacity: 1; transform: translateY(-20px) scale(0) rotate(0deg); }
  60%  { opacity: 1; }
  100% { opacity: 0; transform: translateY(80vh) scale(1.5) rotate(360deg); }
}

/* ===========================
   Celebration Overlay
   =========================== */
.celebration-overlay {
  position: fixed;
  inset: 0;
  background: linear-gradient(135deg, rgba(37,99,235,.92), rgba(29,78,216,.95));
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: 200;
  opacity: 0;
  pointer-events: none;
  transition: opacity .3s ease;
}

.celebration-overlay.show {
  opacity: 1;
  pointer-events: all;
}

.celebration-content {
  text-align: center;
  animation: cel-pop .5s cubic-bezier(.34,1.56,.64,1) both;
}

@keyframes cel-pop {
  from { transform: scale(.5); opacity: 0; }
  to   { transform: scale(1); opacity: 1; }
}

.celebration-content .cel-icon {
  font-size: 5rem;
  display: block;
  margin-bottom: 1rem;
}

.celebration-content h2 {
  font-size: 1.8rem;
  font-weight: 800;
  color: #fff;
  margin-bottom: .5rem;
}

.celebration-content p {
  font-size: 1rem;
  color: var(--blue-200);
}

/* ===========================
   Utility / Responsive
   =========================== */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0,0,0,0);
  white-space: nowrap;
}

@media (min-width: 600px) {
  .top-content,
  .quiz-body {
    padding-left: 2rem;
    padding-right: 2rem;
  }

  .quiz-progress-wrap {
    padding-left: 2rem;
    padding-right: 2rem;
  }

  .question-text { font-size: 1.05rem; }
  .choice-btn    { font-size: .95rem; }
}

@media (min-width: 768px) {
  body {
    display: flex;
    align-items: center;
    justify-content: center;
  }

  #app {
    max-width: 540px;
    min-height: 100vh;
    box-shadow: 0 0 60px rgba(37,99,235,.25);
    border-radius: 0;
  }
}

/* scrollbar styling */
.quiz-body::-webkit-scrollbar { width: 4px; }
.quiz-body::-webkit-scrollbar-track { background: transparent; }
.quiz-body::-webkit-scrollbar-thumb { background: var(--gray-300); border-radius: 99px; }