/* Basic reset */
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
html { height: 100%; }
body {
  min-height: 100%;
  font-family: system-ui, -apple-system, 'Segoe UI', Roboto, Helvetica, Arial, 'Apple Color Emoji', 'Segoe UI Emoji';
  line-height: 1.5;
  color: #111;
  background: #f7f7fb;
}

/* Layout */
.app-header {
  padding: 1.25rem 1rem 0.5rem;
  text-align: center;
}
.app-header h1 {
  margin: 0.25rem 0;
  font-size: clamp(1.25rem, 2.5vw, 1.75rem);
}
.tagline { color: #444; margin-top: 0.25rem; }

.app-main { max-width: 1100px; margin: 0 auto; padding: 0 1rem 2rem; }

.controls {
  background: white;
  border: 1px solid #e6e6ef;
  border-radius: 12px;
  padding: 0.75rem;
  margin-bottom: 1rem;
  box-shadow: 0 1px 0 rgba(0,0,0,0.03);
}
.controls-row {
  display: flex; flex-wrap: wrap; gap: 0.5rem 0.75rem; align-items: center; justify-content: space-between;
}
.controls-row label { font-weight: 600; }
.controls-row select { padding: 0.4rem 0.5rem; border-radius: 8px; border: 1px solid #ccc; }

.mode-toggle {
  display: inline-flex; align-items: center; gap: 0.4rem;
  margin-left: auto;
}

.stats {
  display: flex; gap: 1.25rem; margin-top: 0.5rem; flex-wrap: wrap;
}

.btn {
  border: 1px solid #d0d0e0;
  background: #fff;
  padding: 0.45rem 0.75rem;
  border-radius: 10px;
  cursor: pointer;
  font-weight: 600;
}
.btn:hover { background: #f2f2fa; }
.btn.primary {
  background: #3a6df0; color: white; border-color: #2d5ee8;
}
.btn.primary:hover { background: #2d5ee8; }

/* Game board */
.board {
  display: grid;
  gap: 12px;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  align-items: stretch;
}
.card {
  position: relative;
  perspective: 1000px;
  min-height: 120px;
  border-radius: 12px;
}
.card-inner {
  position: absolute;
  inset: 0;
  transition: transform 0.5s;
  transform-style: preserve-3d;
  border-radius: 12px;
}
.card.flipped .card-inner { transform: rotateY(180deg); }
.card.matched { outline: 3px solid #2fbf71; }

.card-face {
  position: absolute; inset: 0;
  backface-visibility: hidden;
  background: white;
  border: 1px solid #e6e6ef;
  border-radius: 12px;
  padding: 0.75rem;
  display: flex; flex-direction: column;
}
.card-front { justify-content: center; align-items: center; }
.card-back { transform: rotateY(180deg); }

.face-label {
  font-size: 0.75rem; font-weight: 700; letter-spacing: 0.04em; color: #666;
  text-transform: uppercase;
}
.face-content {
  margin-top: 0.25rem;
  font-size: 0.95rem;
}
.term { font-weight: 700; }

/* Study mode */
.hidden { display: none !important; }

.study-card {
  background: white;
  border: 1px solid #e6e6ef;
  border-radius: 12px;
  padding: 1rem;
  margin-top: 0.5rem;
}
.flashcard {
  width: min(700px, 95%);
  height: 260px;
  margin: 0.5rem auto 0.75rem;
  perspective: 1000px;
  outline: none;
}
.flashcard-inner {
  position: relative; width: 100%; height: 100%;
  transform-style: preserve-3d;
  transition: transform 0.5s;
  border-radius: 12px;
}
.flashcard.flipped .flashcard-inner { transform: rotateY(180deg); }
.flashcard-face {
  position: absolute; inset: 0;
  backface-visibility: hidden;
  background: #fff;
  border: 1px solid #e6e6ef;
  border-radius: 12px;
  padding: 1rem;
  display: flex; flex-direction: column;
}
.flashcard-front { justify-content: center; }
.flashcard-back { transform: rotateY(180deg); overflow-y: auto; }
.study-controls {
  display: flex; gap: 0.5rem; justify-content: center; align-items: center; flex-wrap: wrap;
}
.toggle-def { display: inline-flex; align-items: center; gap: 0.4rem; }

/* Dialog */
.dialog {
  border: none;
  border-radius: 12px;
  padding: 1rem 1.25rem;
  max-width: 420px;
  width: calc(100% - 2rem);
}
.dialog::backdrop { background: rgba(0,0,0,0.35); }
.dialog menu { display: flex; gap: 0.5rem; justify-content: flex-end; margin-top: 0.75rem; }
.summary { margin: 0.5rem 0; }

/* Footer */
.app-footer { text-align: center; color: #666; font-size: 0.9rem; padding: 1rem 0 2rem; }
.app-footer a { color: inherit; }

/* Accessibility */
.card[tabindex], .flashcard[tabindex] { outline: 2px solid transparent; }
.card:focus-visible, .flashcard:focus-visible { outline: 3px solid #3a6df0; }