* { margin: 0; padding: 0; box-sizing: border-box; }
:root {
  --red: #e63946; --red-dark: #c1121f; --yellow: #ffd60a; --yellow-dark: #ffc300;
  --blue: #48cae4; --blue-dark: #0096c7; --green: #52b788; --green-dark: #2d6a4f;
  --orange: #ff9f1c; --purple: #9b5de5; --bg: #fff8e7; --card-bg: #ffffff;
  --text: #1d3557; --shadow: 0 4px 15px rgba(0,0,0,0.1); --shadow-hover: 0 8px 25px rgba(0,0,0,0.15);
  --radius: 20px;
}
body { font-family: 'Nunito', sans-serif; background: var(--bg); color: var(--text); min-height: 100vh; overflow-x: hidden; }
.screen { display: none; min-height: 100vh; padding: 20px; max-width: 900px; margin: 0 auto; }
.screen.active { display: block; animation: fadeIn 0.4s ease; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: translateY(0); } }
.hidden { display: none !important; }
.home-container { text-align: center; padding-top: 40px; }
.logo-emoji { font-size: 5rem; animation: bounce 2s infinite; }
@keyframes bounce { 0%,100% { transform: translateY(0); } 50% { transform: translateY(-15px); } }
.main-title { font-family: 'Fredoka', sans-serif; font-size: 3rem; color: var(--red); margin-top: 10px; text-shadow: 2px 2px 0 var(--yellow); }
.sub-title { font-family: 'Fredoka', sans-serif; font-size: 1.8rem; color: var(--blue-dark); margin-bottom: 10px; }
.home-desc { font-size: 1.1rem; color: var(--text); margin-bottom: 30px; line-height: 1.6; }
.menu-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; max-width: 600px; margin: 0 auto; }
.menu-card { background: var(--card-bg); border: none; border-radius: var(--radius); padding: 25px 15px; cursor: pointer; box-shadow: var(--shadow); transition: all 0.3s ease; display: flex; flex-direction: column; align-items: center; gap: 5px; font-family: 'Nunito', sans-serif; }
.menu-card:hover { transform: translateY(-5px) scale(1.03); box-shadow: var(--shadow-hover); }
.menu-card:active { transform: scale(0.98); }
.menu-card-quiz { border-bottom: 5px solid var(--red); }
.menu-card-match { border-bottom: 5px solid var(--purple); }
.menu-card-flash { border-bottom: 5px solid var(--blue); }
.menu-card-color { border-bottom: 5px solid var(--green); }
.menu-emoji { font-size: 2.5rem; }
.menu-label-vi { font-size: 1.1rem; font-weight: 700; color: var(--text); }
.menu-label-en { font-size: 0.85rem; color: #888; }
.back-btn { background: var(--text); color: #fff; border: none; padding: 10px 20px; border-radius: 50px; font-size: 1rem; cursor: pointer; font-family: 'Nunito', sans-serif; font-weight: 600; margin-bottom: 20px; transition: all 0.2s; }
.back-btn:hover { background: var(--red); transform: translateX(-3px); }
.section-header { text-align: center; margin-bottom: 30px; }
.section-emoji { font-size: 3rem; display: block; margin-bottom: 5px; }
.section-header h1 { font-family: 'Fredoka', sans-serif; font-size: 2rem; color: var(--text); }
.cards-container { display: grid; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); gap: 20px; }
.info-card { perspective: 1000px; height: 280px; cursor: pointer; position: relative; }
.info-card .card-front, .info-card .card-back { position: absolute; width: 100%; height: 100%; backface-visibility: hidden; border-radius: var(--radius); display: flex; flex-direction: column; align-items: center; justify-content: center; padding: 20px; text-align: center; transition: transform 0.6s; }
.info-card .card-front { background: var(--card-bg); box-shadow: var(--shadow); }
.info-card .card-back { background: linear-gradient(135deg, var(--red), var(--orange)); color: #fff; transform: rotateY(180deg); box-shadow: var(--shadow); justify-content: center; gap: 10px; }
.info-card.flipped .card-front { transform: rotateY(180deg); }
.info-card.flipped .card-back { transform: rotateY(0deg); }
.card-emoji { font-size: 3rem; margin-bottom: 10px; }
.card-front h3 { font-family: 'Fredoka', sans-serif; font-size: 1.2rem; color: var(--text); margin-bottom: 5px; }
.card-front h4 { font-size: 0.9rem; color: #888; font-weight: 600; }
.card-hint { font-size: 0.8rem; color: #ccc; margin-top: 15px; }
.card-back .vi-text, .card-back .en-text { font-size: 0.85rem; line-height: 1.5; }
.card-back .vi-text { border-bottom: 1px solid rgba(255,255,255,0.3); padding-bottom: 8px; }
.card-back strong { color: var(--yellow); }
.speak-btn { background: rgba(255,255,255,0.25); color: #fff; border: 2px solid rgba(255,255,255,0.5); padding: 6px 16px; border-radius: 50px; font-size: 0.85rem; cursor: pointer; font-family: 'Nunito', sans-serif; font-weight: 700; transition: all 0.2s; margin-top: 8px; }
.speak-btn:hover { background: rgba(255,255,255,0.4); transform: scale(1.05); }
.speak-btn:active { transform: scale(0.95); }
.speak-btn-flash { background: var(--green); font-size: 0.9rem; padding: 12px 20px; }
.speak-btn-flash:hover { background: var(--green-dark); }
.quiz-start { text-align: center; padding: 50px 20px; }
.quiz-intro { font-family: 'Fredoka', sans-serif; font-size: 2rem; color: var(--text); margin-bottom: 5px; }
.quiz-intro-sub { font-size: 1.2rem; color: #888; margin-bottom: 30px; }
.big-btn { background: var(--red); color: #fff; border: none; padding: 15px 40px; border-radius: 50px; font-size: 1.2rem; font-weight: 700; cursor: pointer; font-family: 'Fredoka', sans-serif; box-shadow: 0 4px 15px rgba(230,57,70,0.4); transition: all 0.2s; margin: 10px; }
.big-btn:hover { transform: scale(1.05); background: var(--red-dark); }
.big-btn:active { transform: scale(0.95); }
.btn-secondary { background: var(--blue-dark); box-shadow: 0 4px 15px rgba(0,150,199,0.4); }
.btn-secondary:hover { background: var(--blue); }
.quiz-progress { display: flex; justify-content: space-between; align-items: center; margin-bottom: 10px; font-weight: 700; font-size: 1.1rem; }
.quiz-progress-bar { height: 10px; background: #e0e0e0; border-radius: 50px; overflow: hidden; margin-bottom: 25px; }
.quiz-bar-fill { height: 100%; background: linear-gradient(90deg, var(--green), var(--blue)); border-radius: 50px; width: 0%; transition: width 0.3s ease; }
.quiz-question-text { font-size: 1.3rem; font-weight: 700; margin-bottom: 20px; line-height: 1.5; text-align: center; }
.quiz-options { display: grid; gap: 12px; }
.quiz-option { background: var(--card-bg); border: 3px solid #e0e0e0; border-radius: 15px; padding: 15px 20px; font-size: 1.1rem; cursor: pointer; font-family: 'Nunito', sans-serif; font-weight: 600; transition: all 0.2s; text-align: left; }
.quiz-option:hover { border-color: var(--blue); transform: translateX(5px); }
.quiz-option.correct { background: var(--green); color: #fff; border-color: var(--green-dark); animation: pulse 0.5s; }
.quiz-option.wrong { background: var(--red); color: #fff; border-color: var(--red-dark); animation: shake 0.5s; }
.quiz-option.disabled { pointer-events: none; opacity: 0.6; }
@keyframes pulse { 0%,100% { transform: scale(1); } 50% { transform: scale(1.05); } }
@keyframes shake { 0%,100% { transform: translateX(0); } 25% { transform: translateX(-8px); } 75% { transform: translateX(8px); } }
.quiz-feedback { text-align: center; font-size: 1.2rem; font-weight: 700; margin-top: 15px; min-height: 30px; }
.quiz-feedback.correct { color: var(--green-dark); }
.quiz-feedback.wrong { color: var(--red); }
.quiz-result { text-align: center; padding: 40px 20px; }
.result-emoji { font-size: 5rem; animation: bounce 1s 3; }
.quiz-result h2 { font-family: 'Fredoka', sans-serif; font-size: 2rem; color: var(--text); margin: 10px 0; }
#result-score { font-size: 1.5rem; font-weight: 700; color: var(--red); margin-bottom: 10px; }
#result-message { font-size: 1.1rem; color: #666; margin-bottom: 25px; line-height: 1.5; }
.game-instruction { text-align: center; font-size: 1.1rem; font-weight: 600; margin-bottom: 20px; color: var(--text); }
.match-score-bar { display: flex; justify-content: space-between; font-weight: 700; font-size: 1.1rem; margin-bottom: 20px; }
.match-board { display: grid; grid-template-columns: 1fr 1fr; gap: 15px; max-width: 600px; margin: 0 auto; }
.match-column { display: grid; gap: 10px; }
.match-item { background: var(--card-bg); border: 3px solid #e0e0e0; border-radius: 15px; padding: 15px; text-align: center; font-size: 1rem; font-weight: 600; cursor: pointer; transition: all 0.2s; user-select: none; }
.match-item:hover { border-color: var(--purple); transform: scale(1.03); }
.match-item.selected { background: var(--purple); color: #fff; border-color: var(--purple); }
.match-item.matched { background: var(--green); color: #fff; border-color: var(--green-dark); pointer-events: none; animation: pulse 0.5s; }
.match-item.wrong { background: var(--red); color: #fff; border-color: var(--red-dark); animation: shake 0.5s; }
.match-result { text-align: center; padding: 40px 20px; }
.flashcard-counter { text-align: center; font-weight: 700; font-size: 1.2rem; margin-bottom: 20px; color: var(--text); }
.flashcard-wrapper { perspective: 1000px; max-width: 400px; margin: 0 auto 30px; }
.flashcard { width: 100%; height: 300px; cursor: pointer; }
.flashcard-inner { position: relative; width: 100%; height: 100%; transition: transform 0.6s; transform-style: preserve-3d; }
.flashcard.flipped .flashcard-inner { transform: rotateY(180deg); }
.flashcard-front, .flashcard-back { position: absolute; width: 100%; height: 100%; backface-visibility: hidden; border-radius: var(--radius); display: flex; flex-direction: column; align-items: center; justify-content: center; padding: 30px; text-align: center; box-shadow: var(--shadow); }
.flashcard-front { background: linear-gradient(135deg, var(--blue), var(--blue-dark)); color: #fff; }
.flashcard-back { background: linear-gradient(135deg, var(--yellow), var(--orange)); color: var(--text); transform: rotateY(180deg); }
.flashcard-emoji { font-size: 4rem; margin-bottom: 15px; }
.flashcard-word-vi { font-family: 'Fredoka', sans-serif; font-size: 1.8rem; }
.flashcard-word-en { font-family: 'Fredoka', sans-serif; font-size: 1.5rem; margin-bottom: 10px; }
.flashcard-desc { font-size: 0.9rem; line-height: 1.5; }
.flashcard-nav { display: flex; justify-content: center; gap: 20px; }
.nav-btn { background: var(--text); color: #fff; border: none; padding: 12px 30px; border-radius: 50px; font-size: 1rem; font-weight: 600; cursor: pointer; font-family: 'Nunito', sans-serif; transition: all 0.2s; }
.nav-btn:hover { background: var(--blue-dark); transform: scale(1.05); }
.nav-btn:active { transform: scale(0.95); }
.coloring-layout { display: flex; gap: 20px; align-items: flex-start; justify-content: center; flex-wrap: wrap; }
.color-palette { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; padding: 15px; background: var(--card-bg); border-radius: var(--radius); box-shadow: var(--shadow); position: sticky; top: 20px; }
.color-swatch { width: 45px; height: 45px; border-radius: 50%; border: 3px solid #ddd; cursor: pointer; transition: all 0.2s; }
.color-swatch:hover { transform: scale(1.15); border-color: #aaa; }
.color-swatch.active-color { border: 4px solid var(--text); transform: scale(1.15); box-shadow: 0 0 10px rgba(0,0,0,0.2); }
.coloring-canvas-area { flex: 1; max-width: 500px; background: var(--card-bg); border-radius: var(--radius); box-shadow: var(--shadow); padding: 15px; }
#coloring-svg { width: 100%; height: auto; border-radius: 10px; }
.coloring-actions { display: flex; justify-content: center; gap: 15px; margin-top: 20px; }
.confetti { position: fixed; width: 10px; height: 10px; pointer-events: none; z-index: 9999; animation: confettiFall 3s linear forwards; }
@keyframes confettiFall { 0% { transform: translateY(-100vh) rotate(0deg); opacity: 1; } 100% { transform: translateY(100vh) rotate(720deg); opacity: 0; } }
.star-pop { position: fixed; font-size: 2rem; pointer-events: none; z-index: 9999; animation: starPop 1s ease forwards; }
@keyframes starPop { 0% { transform: scale(0) translateY(0); opacity: 1; } 50% { transform: scale(1.5) translateY(-30px); opacity: 1; } 100% { transform: scale(1) translateY(-60px); opacity: 0; } }
@media (max-width: 700px) {
  .menu-grid { grid-template-columns: repeat(2, 1fr); }
  .main-title { font-size: 2.2rem; }
  .sub-title { font-size: 1.4rem; }
  .quiz-question-text { font-size: 1.1rem; }
  .cards-container { grid-template-columns: 1fr; }
  .coloring-layout { flex-direction: column; align-items: center; }
  .color-palette { position: static; grid-template-columns: repeat(8, 1fr); }
  .color-swatch { width: 35px; height: 35px; }
}
@media (max-width: 450px) {
  .menu-grid { grid-template-columns: 1fr; }
  .home-container { padding-top: 20px; }
  .logo-emoji { font-size: 4rem; }
  .main-title { font-size: 1.8rem; }
  .section-header h1 { font-size: 1.5rem; }
  .match-board { grid-template-columns: 1fr; gap: 10px; }
  .match-column { gap: 8px; }
  .match-item { padding: 12px; font-size: 0.9rem; }
}