.sm-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: .75rem;
  max-width: 520px;
  margin: 0 auto;
}
@media (max-width: 520px) {
  .sm-grid { grid-template-columns: repeat(3, 1fr); max-width: 360px; }
}
.sm-card {
  aspect-ratio: 3 / 4;
  perspective: 800px;
  cursor: pointer;
}
.sm-card__inner {
  position: relative;
  width: 100%;
  height: 100%;
  transition: transform .45s ease;
  transform-style: preserve-3d;
}
.sm-card.is-flip .sm-card__inner,
.sm-card.is-done .sm-card__inner { transform: rotateY(180deg); }
.sm-card__face {
  position: absolute;
  inset: 0;
  border-radius: 12px;
  display: grid;
  place-items: center;
  backface-visibility: hidden;
  box-shadow: 0 5px 0 rgba(0,0,0,.35);
  font-family: 'Caveat', cursive;
}
.sm-card__back {
  background: linear-gradient(180deg, var(--slate-600), var(--slate-800));
  border: 2px solid rgba(255,255,255,.12);
  color: var(--chalk-dim);
  font-size: 2.2rem;
}
.sm-card__front {
  background: linear-gradient(180deg, #f7f3e8, #e7e0c7);
  color: var(--slate-900);
  transform: rotateY(180deg);
  text-align: center;
  padding: .5rem;
  font-size: clamp(1.5rem, 4vw, 2rem);
  font-weight: 700;
}
.sm-card__front--pic { font-size: clamp(2.6rem, 8vw, 3.6rem); }
.sm-card.is-done .sm-card__face { opacity: .35; }
.sm-controls {
  display: flex;
  justify-content: center;
  margin-top: 1.25rem;
}