:root {
  --vocab-primary: #4f46e5;
  --vocab-primary-light: #818cf8;
  --vocab-success: #22c55e;
  --vocab-warning: #f59e0b;
  --vocab-danger: #ef4444;
  --vocab-bg: #f8fafc;
}

body {
  font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--vocab-bg);
}

/* ===== Hero ===== */
.vocab-hero {
  background: linear-gradient(135deg, var(--vocab-primary) 0%, #7c3aed 100%);
  color: #fff;
  padding: 4rem 1rem;
}
.vocab-hero h1 { color: #fff; }
.vocab-hero .lead { color: rgba(255,255,255,.9); }

/* ===== Grade Card ===== */
.grade-card {
  display: block;
  background: #fff;
  border-radius: 1rem;
  padding: 1.5rem 1rem;
  text-align: center;
  box-shadow: 0 2px 8px rgba(0,0,0,.06);
  transition: all .2s;
  border: 2px solid transparent;
}
.grade-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 24px rgba(79,70,229,.15);
  border-color: var(--vocab-primary);
}
.grade-icon {
  font-size: 2rem;
  font-weight: 800;
  color: var(--vocab-primary);
}
.grade-label {
  font-size: 1rem;
  font-weight: 600;
  margin-top: .5rem;
  color: #1e293b;
}
.grade-desc {
  font-size: .85rem;
  color: #64748b;
  margin-top: .25rem;
}

/* ===== Feature Card ===== */
.feature-card {
  background: #fff;
  border-radius: 1rem;
  box-shadow: 0 2px 8px rgba(0,0,0,.04);
  height: 100%;
}
.feature-icon {
  font-size: 2.5rem;
  color: var(--vocab-primary);
}

/* ===== Flashcard ===== */
.flashcard-container {
  perspective: 1200px;
  max-width: 480px;
  margin: 0 auto;
}
.flashcard {
  position: relative;
  width: 100%;
  min-height: 320px;
  cursor: pointer;
  transform-style: preserve-3d;
  transition: transform .5s;
}
.flashcard.flipped { transform: rotateY(180deg); }
.flashcard-face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  border-radius: 1.5rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 2rem;
  box-shadow: 0 8px 32px rgba(0,0,0,.1);
}
.flashcard-front {
  background: linear-gradient(135deg, #fff 0%, #eef2ff 100%);
}
.flashcard-back {
  background: linear-gradient(135deg, var(--vocab-primary) 0%, #7c3aed 100%);
  color: #fff;
  transform: rotateY(180deg);
}
.flashcard-word {
  font-size: 2.5rem;
  font-weight: 800;
  color: #1e293b;
}
.flashcard-meaning {
  font-size: 1.8rem;
  font-weight: 600;
  color: #fff;
}
.flashcard-example {
  font-size: .95rem;
  margin-top: 1rem;
  opacity: .85;
  text-align: center;
}
.flashcard-mastery {
  margin-top: 1rem;
}
.mastery-star {
  font-size: 1.2rem;
  margin: 0 2px;
}
.mastery-star.filled { color: #f59e0b; }
.mastery-star.empty { color: #cbd5e1; }

/* ===== Quiz ===== */
.quiz-option {
  display: block;
  width: 100%;
  padding: 1rem 1.5rem;
  margin-bottom: .75rem;
  background: #fff;
  border: 2px solid #e2e8f0;
  border-radius: .75rem;
  font-size: 1.1rem;
  cursor: pointer;
  transition: all .15s;
  text-align: left;
}
.quiz-option:hover {
  border-color: var(--vocab-primary);
  background: #eef2ff;
}
.quiz-option.correct {
  border-color: var(--vocab-success);
  background: #dcfce7;
  color: #166534;
}
.quiz-option.wrong {
  border-color: var(--vocab-danger);
  background: #fee2e2;
  color: #991b1b;
}
.quiz-option.disabled {
  pointer-events: none;
  opacity: .6;
}

.spelling-input {
  font-size: 1.5rem;
  padding: 1rem;
  border: 3px solid #e2e8f0;
  border-radius: .75rem;
  text-align: center;
  width: 100%;
  max-width: 400px;
  outline: none;
  transition: border-color .2s;
}
.spelling-input:focus { border-color: var(--vocab-primary); }
.spelling-input.correct { border-color: var(--vocab-success); background: #dcfce7; }
.spelling-input.wrong { border-color: var(--vocab-danger); background: #fee2e2; }

/* ===== Progress ===== */
.progress-ring {
  width: 160px;
  height: 160px;
}
.progress-ring circle {
  fill: none;
  stroke-width: 12;
  stroke-linecap: round;
  transform: rotate(-90deg);
  transform-origin: center;
}
.progress-ring .bg { stroke: #e2e8f0; }
.progress-ring .fg { stroke: var(--vocab-primary); transition: stroke-dashoffset .8s; }

.stat-card {
  background: #fff;
  border-radius: 1rem;
  padding: 1.5rem;
  text-align: center;
  box-shadow: 0 2px 8px rgba(0,0,0,.04);
}
.stat-value {
  font-size: 2rem;
  font-weight: 800;
  color: var(--vocab-primary);
}
.stat-label {
  font-size: .85rem;
  color: #64748b;
  margin-top: .25rem;
}

/* ===== Responsive ===== */
@media (max-width: 576px) {
  .flashcard-word { font-size: 1.8rem; }
  .flashcard-meaning { font-size: 1.3rem; }
  .flashcard { min-height: 260px; }
  .vocab-hero { padding: 2.5rem 1rem; }
}