*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --green: #2E7D32;
  --green-dark: #1B5E20;
  --green-light: #E8F5E9;
  --accent: #FF6F00;
  --correct: #2E7D32;
  --wrong: #C62828;
  --text: #212121;
  --text-sub: #757575;
  --bg: #F5F5F5;
  --white: #ffffff;
  --radius: 12px;
  --shadow: 0 2px 8px rgba(0,0,0,0.12);
}

html, body {
  height: 100%;
  font-family: "Hiragino Sans", "Hiragino Kaku Gothic ProN", "Noto Sans JP", sans-serif;
  background: var(--bg);
  color: var(--text);
  -webkit-text-size-adjust: 100%;
}

/* ===== 画面切り替え ===== */
.screen { display: none; min-height: 100svh; }
.screen.active { display: flex; flex-direction: column; }

/* ===== ホーム画面 ===== */
#screen-home {
  background: linear-gradient(160deg, var(--green-dark) 0%, var(--green) 100%);
  align-items: center;
  justify-content: center;
  padding: 2rem 1.5rem;
}

.home-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
  width: 100%;
  max-width: 400px;
}

.home-icon { font-size: 4rem; }

.home-title {
  color: var(--white);
  font-size: 1.8rem;
  font-weight: bold;
  letter-spacing: .05em;
}

.home-sub {
  color: rgba(255,255,255,0.8);
  font-size: .95rem;
}

.home-stats {
  background: rgba(255,255,255,0.15);
  border-radius: var(--radius);
  padding: .8rem 1.5rem;
  color: var(--white);
  font-size: .9rem;
  text-align: center;
  width: 100%;
  min-height: 2.5rem;
}

/* ===== ボタン ===== */
.btn-primary, .btn-secondary, .btn-back {
  border: none;
  cursor: pointer;
  font-family: inherit;
  font-weight: bold;
  transition: transform 0.1s, opacity 0.1s;
}
.btn-primary:active, .btn-secondary:active { transform: scale(0.97); opacity: .85; }

.btn-primary {
  width: 100%;
  padding: 1rem;
  border-radius: var(--radius);
  background: var(--white);
  color: var(--green-dark);
  font-size: 1.05rem;
}

.btn-secondary {
  width: 100%;
  padding: .85rem;
  border-radius: var(--radius);
  background: rgba(255,255,255,0.2);
  color: var(--white);
  font-size: .95rem;
}

.btn-back {
  background: none;
  color: var(--white);
  font-size: 1.4rem;
  padding: .3rem .6rem;
  border-radius: 8px;
}

/* ===== クイズ画面 ===== */
#screen-quiz { background: var(--green-dark); }

.quiz-header {
  display: flex;
  align-items: center;
  gap: .8rem;
  padding: .8rem 1rem;
  background: var(--green-dark);
}

.progress-wrap {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: .3rem;
}

.progress-bar {
  height: 6px;
  background: rgba(255,255,255,0.3);
  border-radius: 3px;
  overflow: hidden;
}

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

.progress-text {
  color: rgba(255,255,255,0.8);
  font-size: .75rem;
  text-align: right;
}

.quiz-body {
  flex: 1;
  background: var(--bg);
  border-radius: 20px 20px 0 0;
  padding: 1.5rem 1.2rem;
  overflow-y: auto;
}

.question-num {
  font-size: .8rem;
  color: var(--green);
  font-weight: bold;
  margin-bottom: .5rem;
  letter-spacing: .05em;
}

.question-text {
  font-size: 1.1rem;
  line-height: 1.7;
  color: var(--text);
  margin-bottom: 1.5rem;
  font-weight: 500;
}

.choices {
  display: flex;
  flex-direction: column;
  gap: .7rem;
}

.choice-btn {
  display: flex;
  align-items: center;
  gap: .8rem;
  width: 100%;
  padding: .9rem 1rem;
  border-radius: var(--radius);
  border: 2px solid #E0E0E0;
  background: var(--white);
  font-family: inherit;
  font-size: .95rem;
  color: var(--text);
  cursor: pointer;
  text-align: left;
  line-height: 1.5;
  transition: border-color 0.15s, background 0.15s;
}

.choice-btn:active { transform: scale(0.98); }

.choice-label {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--bg);
  font-size: .8rem;
  font-weight: bold;
  color: var(--text-sub);
  flex-shrink: 0;
}

.choice-btn.correct {
  border-color: var(--correct);
  background: #E8F5E9;
}
.choice-btn.correct .choice-label {
  background: var(--correct);
  color: var(--white);
}

.choice-btn.wrong {
  border-color: var(--wrong);
  background: #FFEBEE;
}
.choice-btn.wrong .choice-label {
  background: var(--wrong);
  color: var(--white);
}

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

/* ===== 解説画面 ===== */
#screen-explain { background: var(--bg); }

.explain-header {
  background: var(--green-dark);
  padding: 1.2rem 1.2rem .8rem;
}

.result-badge {
  display: inline-flex;
  align-items: center;
  gap: .5rem;
  font-size: 1.1rem;
  font-weight: bold;
  color: var(--white);
  padding: .4rem .9rem;
  border-radius: 20px;
}

.result-badge.correct-badge { background: rgba(255,255,255,0.2); }
.result-badge.wrong-badge { background: rgba(198,40,40,0.6); }

.explain-body {
  flex: 1;
  padding: 1.2rem;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.explain-question {
  font-size: .95rem;
  color: var(--text-sub);
  line-height: 1.6;
  padding: .8rem;
  background: var(--white);
  border-radius: var(--radius);
  border-left: 4px solid var(--green);
}

.explain-answer {
  font-size: 1rem;
  font-weight: bold;
  color: var(--green-dark);
  padding: .8rem 1rem;
  background: var(--green-light);
  border-radius: var(--radius);
}

.explain-text {
  font-size: .95rem;
  line-height: 1.8;
  color: var(--text);
  padding: 1rem;
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.explain-footer {
  padding: 1rem 1.2rem;
  background: var(--white);
  border-top: 1px solid #E0E0E0;
}

.explain-footer .btn-primary {
  background: var(--green);
  color: var(--white);
}

/* ===== 結果画面 ===== */
#screen-result {
  background: linear-gradient(160deg, var(--green-dark) 0%, var(--green) 100%);
  align-items: center;
  justify-content: center;
  padding: 2rem 1.5rem;
}

.result-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
  width: 100%;
  max-width: 400px;
}

.result-emoji { font-size: 4rem; }

.result-title {
  color: var(--white);
  font-size: 1.5rem;
  font-weight: bold;
}

.result-score {
  color: var(--white);
  font-size: 2.5rem;
  font-weight: bold;
}

.result-detail {
  color: rgba(255,255,255,0.8);
  font-size: .95rem;
  text-align: center;
  line-height: 1.6;
}

#screen-result .btn-primary {
  width: 100%;
  background: var(--white);
  color: var(--green-dark);
}

#screen-result .btn-secondary {
  width: 100%;
}