html, body, main, header, footer {
  padding: 0px;
  margin: 0px;
}

* {
  box-sizing: border-box;
}

/* ====== CSS Variables ====== */
:root {
  --color-primary: #4f8cff;
  --color-primary-dark: #3a6fd8;
  --color-success: #34c759;
  --color-danger: #ff4757;
  --color-warning: #ffa502;
  --color-bg: #f5f7fb;
  --color-card: #ffffff;
  --color-text: #2c3e50;
  --color-text-light: #7f8c9b;
  --color-border: #e1e5ed;
  --color-tag-naming: #e8f0fe;
  --color-tag-assignment: #e6f7ee;
  --color-tag-unpacking: #fff3e0;
  --color-tag-naming-text: #3a6fd8;
  --color-tag-assignment-text: #1e8e4a;
  --color-tag-unpacking-text: #e67e22;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.08);
}

/* ====== Base ====== */
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

header {
  background: var(--color-card);
  border-bottom: 1px solid var(--color-border);
  height: 56px;
  display: flex;
  align-items: center;
  flex-shrink: 0;
}

.header-inner {
  max-width: 800px;
  width: 100%;
  margin: 0 auto;
  padding: 0 20px;
  display: flex;
  align-items: center;
}

.logo {
  font-size: 18px;
  font-weight: 700;
  color: var(--color-primary);
}

main {
  flex: 1;
  display: flex;
  justify-content: center;
  padding: 24px 16px 40px;
}

footer {
  background: var(--color-card);
  border-top: 1px solid var(--color-border);
  padding: 16px 20px;
  text-align: center;
  flex-shrink: 0;
}

.page-info {
  font-size: 13px;
  color: var(--color-text-light);
}

.page-info a {
  color: var(--color-primary);
  text-decoration: none;
}

/* ====== App Container ====== */
#app {
  max-width: 720px;
  width: 100%;
}

.view {
  display: none;
}

.view.active {
  display: block;
}

/* ====== Home View ====== */
.home-card {
  background: var(--color-card);
  border-radius: var(--radius);
  padding: 48px 36px;
  text-align: center;
  box-shadow: var(--shadow-lg);
}

#home-title {
  font-size: 28px;
  font-weight: 800;
  color: var(--color-text);
  margin: 0 0 12px;
}

.home-desc {
  font-size: 15px;
  color: var(--color-text-light);
  margin: 0 0 28px;
  line-height: 1.7;
}

.home-topics {
  display: flex;
  justify-content: center;
  gap: 12px;
  flex-wrap: wrap;
  margin-bottom: 28px;
}

.topic-badge {
  padding: 8px 16px;
  border-radius: 20px;
  font-size: 13px;
  font-weight: 600;
}

.topic-badge.naming {
  background: var(--color-tag-naming);
  color: var(--color-tag-naming-text);
}

.topic-badge.assignment {
  background: var(--color-tag-assignment);
  color: var(--color-tag-assignment-text);
}

.topic-badge.unpacking {
  background: var(--color-tag-unpacking);
  color: var(--color-tag-unpacking-text);
}

.home-meta {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin-bottom: 32px;
  font-size: 14px;
  color: var(--color-text-light);
}

/* ====== Buttons ====== */
.btn {
  padding: 12px 28px;
  border: none;
  border-radius: 24px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  outline: none;
  font-family: inherit;
  min-height: 44px;
}

.btn:active {
  transform: scale(0.97);
}

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

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

.btn-outline {
  background: transparent;
  color: var(--color-primary);
  border: 2px solid var(--color-primary);
}

.btn-outline:hover {
  background: var(--color-tag-naming);
}

.btn-outline:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.btn-outline:disabled:active {
  transform: none;
}

.btn-submit {
  background: var(--color-success);
  color: #fff;
}

.btn-submit:hover {
  background: #2db14e;
}

/* ====== Exam View ====== */
.exam-header {
  background: var(--color-card);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin-bottom: 16px;
  box-shadow: var(--shadow);
  text-align: center;
}

.exam-timer {
  font-size: 36px;
  font-weight: 800;
  color: var(--color-primary);
  letter-spacing: 2px;
  font-variant-numeric: tabular-nums;
  margin-bottom: 12px;
}

.exam-timer.warning {
  color: var(--color-danger);
  animation: pulse 1s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

.exam-progress-bar {
  height: 6px;
  background: var(--color-border);
  border-radius: 3px;
  overflow: hidden;
  margin-bottom: 14px;
}

.exam-progress-fill {
  height: 100%;
  background: var(--color-primary);
  border-radius: 3px;
  transition: width 0.3s ease;
}

.exam-dots {
  display: flex;
  justify-content: center;
  gap: 8px;
  flex-wrap: wrap;
}

.exam-dot {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--color-border);
  border: none;
  cursor: pointer;
  font-size: 12px;
  font-weight: 600;
  color: var(--color-text-light);
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 28px;
  min-width: 28px;
}

.exam-dot.current {
  background: var(--color-primary);
  color: #fff;
  transform: scale(1.15);
}

.exam-dot.answered {
  background: var(--color-success);
  color: #fff;
}

.exam-dot.answered.current {
  background: var(--color-primary);
}

/* ====== Exam Body ====== */
.exam-body {
  background: var(--color-card);
  border-radius: var(--radius);
  padding: 28px 24px;
  margin-bottom: 16px;
  box-shadow: var(--shadow);
  min-height: 260px;
}

.exam-question-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
  gap: 12px;
  flex-wrap: wrap;
}

.exam-q-num {
  font-size: 14px;
  color: var(--color-text-light);
  font-weight: 600;
}

.exam-q-topic {
  font-size: 12px;
  padding: 4px 12px;
  border-radius: 12px;
  font-weight: 600;
  color: var(--color-text-light);
}

.exam-question-text {
  font-size: 17px;
  font-weight: 500;
  margin: 0 0 20px;
  line-height: 1.7;
}

.exam-options {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.option-btn {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 18px;
  border: 2px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-card);
  cursor: pointer;
  font-size: 15px;
  font-family: inherit;
  text-align: left;
  transition: all 0.15s ease;
  min-height: 44px;
}

.option-btn:hover {
  border-color: var(--color-primary);
  background: #f0f5ff;
}

.option-btn.selected {
  border-color: var(--color-primary);
  background: #e8f0ff;
  font-weight: 600;
}

.option-btn.correct {
  border-color: var(--color-success);
  background: #e6f7ee;
}

.option-btn.wrong {
  border-color: var(--color-danger);
  background: #ffebed;
}

.option-letter {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: var(--color-bg);
  font-weight: 700;
  font-size: 14px;
  flex-shrink: 0;
}

.option-btn.selected .option-letter {
  background: var(--color-primary);
  color: #fff;
}

.option-btn.correct .option-letter {
  background: var(--color-success);
  color: #fff;
}

.option-btn.wrong .option-letter {
  background: var(--color-danger);
  color: #fff;
}

.option-text {
  flex: 1;
}

.exam-explanation {
  margin-top: 20px;
  padding: 16px 18px;
  background: #fef9e7;
  border-left: 4px solid var(--color-warning);
  border-radius: 4px;
  font-size: 14px;
  line-height: 1.7;
  color: #7d6608;
}

/* ====== Exam Footer ====== */
.exam-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}

.exam-footer .btn {
  flex: 1;
  text-align: center;
  white-space: nowrap;
}

#btn-submit {
  flex: 1.2;
}

/* ====== Result View ====== */
.result-header {
  background: var(--color-card);
  border-radius: var(--radius);
  padding: 36px 24px;
  text-align: center;
  box-shadow: var(--shadow);
  margin-bottom: 16px;
}

.result-score-ring {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  width: 120px;
  height: 120px;
  border-radius: 50%;
  border: 6px solid var(--color-primary);
  margin: 0 auto 16px;
}

.result-score-ring.great {
  border-color: var(--color-success);
}

.result-score-ring.good {
  border-color: var(--color-primary);
}

.result-score-ring.fair {
  border-color: var(--color-warning);
}

.result-score-ring.poor {
  border-color: var(--color-danger);
}

.result-score-num {
  font-size: 40px;
  font-weight: 800;
  color: var(--color-text);
  line-height: 1;
}

.result-score-label {
  font-size: 13px;
  color: var(--color-text-light);
  margin-top: 2px;
}

#result-title {
  font-size: 22px;
  font-weight: 700;
  margin: 0;
}

/* ====== Recommendation ====== */
.result-recommendation {
  background: var(--color-card);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin-bottom: 16px;
  box-shadow: var(--shadow);
  border-left: 5px solid var(--color-primary);
}

.result-recommendation h3 {
  margin: 0 0 10px;
  font-size: 16px;
  color: var(--color-primary);
}

.result-recommendation p {
  margin: 0;
  font-size: 14px;
  line-height: 1.7;
}

.result-recommendation ul {
  margin: 8px 0 0;
  padding-left: 18px;
  font-size: 14px;
  line-height: 1.8;
}

/* ====== Topic Breakdown ====== */
.result-topics {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-bottom: 16px;
}

.result-topic-row {
  display: flex;
  align-items: center;
  gap: 12px;
  background: var(--color-card);
  border-radius: var(--radius-sm);
  padding: 14px 18px;
  box-shadow: var(--shadow);
}

.result-topic-label {
  font-size: 14px;
  font-weight: 600;
  min-width: 120px;
}

.result-topic-bar-wrap {
  flex: 1;
  height: 10px;
  background: var(--color-border);
  border-radius: 5px;
  overflow: hidden;
}

.result-topic-bar-fill {
  height: 100%;
  border-radius: 5px;
  transition: width 0.6s ease;
}

.result-topic-bar-fill.high {
  background: var(--color-success);
}

.result-topic-bar-fill.mid {
  background: var(--color-primary);
}

.result-topic-bar-fill.low {
  background: var(--color-danger);
}

.result-topic-pct {
  font-size: 14px;
  font-weight: 700;
  min-width: 44px;
  text-align: right;
}

/* ====== Question Review ====== */
.result-review {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 24px;
}

.review-item {
  background: var(--color-card);
  border-radius: var(--radius-sm);
  padding: 18px 20px;
  box-shadow: var(--shadow);
  border-left: 4px solid var(--color-border);
}

.review-item.correct-review {
  border-left-color: var(--color-success);
}

.review-item.wrong-review {
  border-left-color: var(--color-danger);
}

.review-item.unanswered-review {
  border-left-color: var(--color-warning);
}

.review-q-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
  flex-wrap: wrap;
  gap: 8px;
}

.review-q-num {
  font-size: 13px;
  font-weight: 600;
  color: var(--color-text-light);
}

.review-q-status {
  font-size: 12px;
  font-weight: 700;
  padding: 2px 10px;
  border-radius: 10px;
}

.review-q-status.correct-status {
  background: #e6f7ee;
  color: #1e8e4a;
}

.review-q-status.wrong-status {
  background: #ffebed;
  color: #d63031;
}

.review-q-status.unanswered-status {
  background: #fff3e0;
  color: #e67e22;
}

.review-q-text {
  font-size: 14px;
  font-weight: 500;
  margin: 0 0 10px;
  line-height: 1.6;
}

.review-q-answer {
  font-size: 13px;
  color: var(--color-text-light);
  margin-bottom: 6px;
}

.review-q-answer span {
  font-weight: 600;
}

.review-q-answer .correct-answer {
  color: var(--color-success);
}

.review-q-answer .wrong-answer {
  color: var(--color-danger);
}

.review-q-explanation {
  font-size: 13px;
  line-height: 1.7;
  color: #7d6608;
  background: #fef9e7;
  padding: 10px 14px;
  border-radius: 6px;
  margin-top: 8px;
}

/* ====== Result Actions ====== */
.result-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

.result-actions .btn {
  min-width: 140px;
}

/* ====== Modal Overlay ====== */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
}

.modal-box {
  background: var(--color-card);
  border-radius: var(--radius);
  padding: 32px 28px;
  max-width: 420px;
  width: 90%;
  text-align: center;
  box-shadow: var(--shadow-lg);
}

.modal-box h3 {
  margin: 0 0 12px;
  font-size: 18px;
}

.modal-box p {
  margin: 0 0 24px;
  font-size: 14px;
  color: var(--color-text-light);
  line-height: 1.6;
}

.modal-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
}

.modal-actions .btn {
  min-width: 100px;
}

/* ====== Responsive ====== */
@media (max-width:575.98px) {
  /* header */
  header {
    height: 44px;
  }

  .logo {
    font-size: 15px;
  }

  /* main */
  main {
    padding: 12px 8px 16px;
  }

  /* home */
  .home-card {
    padding: 28px 18px;
  }

  #home-title {
    font-size: x-large;
    margin-bottom: 8px;
  }

  .home-desc {
    font-size: 13px;
    margin-bottom: 18px;
  }

  .home-meta {
    flex-direction: column;
    gap: 6px;
    align-items: center;
    margin-bottom: 22px;
    font-size: 13px;
  }

  .home-topics {
    gap: 6px;
    margin-bottom: 20px;
  }

  .topic-badge {
    font-size: 12px;
    padding: 5px 10px;
  }

  /* buttons */
  .btn {
    padding: 10px 18px;
    font-size: 14px;
    min-height: 40px;
  }

  /* exam header */
  .exam-header {
    padding: 12px 12px;
    margin-bottom: 10px;
  }

  .exam-timer {
    font-size: 26px;
    margin-bottom: 8px;
  }

  .exam-progress-bar {
    height: 4px;
    margin-bottom: 10px;
  }

  .exam-dots {
    gap: 5px;
  }

  .exam-dot {
    width: 24px;
    height: 24px;
    font-size: 11px;
    min-height: 24px;
    min-width: 24px;
  }

  /* exam body */
  .exam-body {
    padding: 16px 12px;
    margin-bottom: 10px;
    min-height: auto;
  }

  .exam-question-header {
    margin-bottom: 10px;
  }

  .exam-q-num {
    font-size: 12px;
  }

  .exam-q-topic {
    font-size: 11px;
    padding: 2px 8px;
  }

  .exam-question-text {
    font-size: 14px;
    margin-bottom: 14px;
    line-height: 1.5;
  }

  .exam-options {
    gap: 7px;
  }

  .option-btn {
    padding: 10px 12px;
    font-size: 13px;
    min-height: 40px;
    gap: 8px;
  }

  .option-letter {
    width: 26px;
    height: 26px;
    font-size: 12px;
  }

  .exam-explanation {
    margin-top: 14px;
    padding: 12px 14px;
    font-size: 12px;
  }

  /* exam footer */
  .exam-footer {
    flex-direction: column;
    gap: 8px;
  }

  .exam-footer .btn {
    width: 100%;
  }

  /* result */
  .result-header {
    padding: 24px 16px;
    margin-bottom: 10px;
  }

  .result-score-ring {
    width: 90px;
    height: 90px;
    border-width: 5px;
    margin-bottom: 10px;
  }

  .result-score-num {
    font-size: 28px;
  }

  .result-score-label {
    font-size: 11px;
  }

  #result-title {
    font-size: 18px;
  }

  /* recommendation */
  .result-recommendation {
    padding: 14px 16px;
    margin-bottom: 10px;
    border-left-width: 4px;
  }

  .result-recommendation p {
    font-size: 13px;
  }

  .result-recommendation ul {
    font-size: 12px;
    line-height: 1.6;
    padding-left: 14px;
    margin-top: 4px;
  }

  /* topic breakdown */
  .result-topics {
    gap: 6px;
    margin-bottom: 10px;
  }

  .result-topic-row {
    padding: 10px 12px;
    flex-wrap: wrap;
  }

  .result-topic-label {
    font-size: 12px;
    min-width: auto;
    flex: 0 0 100%;
  }

  .result-topic-bar-wrap {
    height: 8px;
  }

  .result-topic-pct {
    font-size: 12px;
  }

  /* question review */
  .result-review {
    gap: 8px;
    margin-bottom: 16px;
  }

  .review-item {
    padding: 12px 14px;
    border-left-width: 3px;
  }

  .review-q-num {
    font-size: 11px;
  }

  .review-q-text {
    font-size: 13px;
    margin-bottom: 6px;
    line-height: 1.5;
  }

  .review-q-answer {
    font-size: 12px;
    margin-bottom: 4px;
  }

  .review-q-explanation {
    font-size: 12px;
    padding: 8px 10px;
    margin-top: 6px;
    line-height: 1.5;
  }

  .review-q-status {
    font-size: 11px;
  }

  /* result actions */
  .result-actions {
    gap: 8px;
  }

  .result-actions .btn {
    min-width: 110px;
  }

  /* footer */
  footer {
    padding: 10px 12px;
  }

  .page-info {
    font-size: 11px;
  }

  /* modal */
  .modal-box {
    padding: 24px 20px;
  }

  .modal-box h3 {
    font-size: 16px;
  }

  .modal-box p {
    font-size: 13px;
    margin-bottom: 18px;
  }

  .modal-actions .btn {
    min-width: 80px;
  }
}