body {
  background: linear-gradient(135deg, #f5f7fa 0%, #e8ecf1 100%);
  min-height: 100vh;
  font-family: 'Segoe UI', system-ui, sans-serif;
}

/* ── Card Scene ── */
.card-scene {
  width: 100%;
  max-width: 560px;
  height: 300px;
  perspective: 1200px;
  cursor: pointer;
}

.card-hiragana-back {
  font-size: 2rem;
}

.card-romaji-back {
  font-size: 1.8rem;
  color: #4b5563;
  margin-top: 0.4rem;
}

@media (max-width: 576px) {
  .card-scene          { height: 340px; }
  .card-main-text      { font-size: 2rem; }
  .card-hiragana       { font-size: 2.2rem; }
  .card-hiragana-back  { font-size: 1.8rem; }
  .card-romaji-back    { font-size: 1.8rem; }
  .card-sub-text       { font-size: 1.4rem; }
}

.card-3d {
  width: 100%;
  height: 100%;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.55s cubic-bezier(0.4, 0.2, 0.2, 1);
}

.card-3d.flipped {
  transform: rotateY(180deg);
}

/* Page-turn slide animation between cards */
@keyframes slideInRight {
  from { opacity: 0; transform: translateX(60px) rotateY(-8deg); }
  to   { opacity: 1; transform: translateX(0) rotateY(0deg); }
}

@keyframes slideInLeft {
  from { opacity: 0; transform: translateX(-60px) rotateY(8deg); }
  to   { opacity: 1; transform: translateX(0) rotateY(0deg); }
}

.card-scene.animate-next .card-3d {
  animation: slideInRight 0.4s ease forwards;
}

.card-scene.animate-prev .card-3d {
  animation: slideInLeft 0.4s ease forwards;
}

/* ── Card Faces ── */
.card-face {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 8px 32px rgba(0,0,0,0.13), 0 2px 8px rgba(0,0,0,0.07);
}

.card-front {
  background: linear-gradient(145deg, #ffffff, #f0f4ff);
  border: 1px solid #dde3f0;
}

.card-back {
  background: linear-gradient(145deg, #eef6ff, #dbeafe);
  border: 1px solid #bfdbfe;
  transform: rotateY(180deg);
}

.card-inner-content {
  text-align: center;
  padding: 1.5rem 2rem;
  width: 100%;
}

/* ── Card Typography ── */
.card-label {
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: #6b7280;
  margin-bottom: 0.5rem;
}

.card-main-text {
  font-size: 2.8rem;
  font-weight: 700;
  color: #1e3a5f;
  line-height: 1.3;
  margin-bottom: 0.25rem;
}

.card-hiragana {
  font-size: 3rem;
  color: #1e3a5f;
  line-height: 1.3;
}

.card-sub-text {
  font-size: 1.5rem;
  color: #4b5563;
  margin-top: 0.4rem;
}

.card-hint {
  font-size: 0.75rem;
  color: #9ca3af;
  margin-top: 0.75rem;
}

.card-type-badge {
  display: inline-block;
  font-size: 0.65rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding: 0.2em 0.6em;
  border-radius: 999px;
  margin-bottom: 0.6rem;
}

.badge-phrase  { background: #fef3c7; color: #92400e; }
.badge-vocab   { background: #d1fae5; color: #065f46; }
.badge-new     { background: #fee2e2; color: #991b1b; margin-left: 0.3rem; }

/* ── Speak Button ── */
.btn-speak {
  border: none;
  background: #3b82f6;
  color: #fff;
  border-radius: 999px;
  padding: 0.35rem 1rem;
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  margin-top: 0.6rem;
  transition: background 0.2s;
}

.btn-speak:hover { background: #2563eb; }

/* ── Action Buttons ── */
#btnKnow, #btnDontKnow {
  min-width: 130px;
  border-radius: 999px;
  font-weight: 600;
  transition: transform 0.15s, box-shadow 0.15s;
}

#btnKnow:hover    { transform: translateY(-2px); box-shadow: 0 4px 16px rgba(34,197,94,0.35); }
#btnDontKnow:hover{ transform: translateY(-2px); box-shadow: 0 4px 16px rgba(239,68,68,0.35); }

/* ── Score Badges ── */
.badge { border-radius: 999px; }

/* ── Options Panel ── */
#optionsPanel .card-body { border-radius: 0.75rem; }