body { display: flex; flex-direction: column; min-height: 100dvh; }

.fc-wrap {
  max-width: 620px;
  margin: 0 auto;
  padding: 2.5rem 1.5rem 4rem;
  flex: 1;
  display: flex;
  flex-direction: column;
  width: 100%;
  box-sizing: border-box;
}

/* Top bar */
.fc-topbar {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
}

.fc-back-link {
  font-family: var(--mono);
  font-size: 0.64rem;
  letter-spacing: 0.04em;
  color: var(--hint);
  text-decoration: none;
  transition: color 0.18s;
  white-space: nowrap;
}
.fc-back-link:hover { color: var(--accent-teal); }

.fc-topic-label {
  font-family: var(--mono);
  font-size: 0.64rem;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--muted);
  flex: 1;
  text-align: center;
}

.fc-counter {
  font-family: var(--mono);
  font-size: 0.64rem;
  color: var(--hint);
  white-space: nowrap;
}

/* Filter toggle */
.fc-filter {
  display: flex;
  gap: 0.35rem;
  justify-content: center;
  margin-bottom: 1.25rem;
}

.fc-filter-btn {
  font-family: var(--mono);
  font-size: 0.62rem;
  letter-spacing: 0.05em;
  padding: 0.32rem 0.85rem;
  border-radius: 4px;
  border: 1px solid var(--border-strong);
  background: none;
  color: var(--muted);
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
}
.fc-filter-btn:hover { color: var(--text); border-color: var(--muted); }
.fc-filter-btn.active {
  background: var(--accent-teal);
  border-color: var(--accent-teal);
  color: #fff;
}
[data-theme="dark"] .fc-filter-btn.active { color: var(--bg); }

/* Progress bar */
.fc-progress {
  width: 100%;
  height: 2px;
  background: var(--border);
  border-radius: 1px;
  margin-bottom: 2rem;
  overflow: hidden;
}
.fc-progress-fill {
  height: 100%;
  background: var(--accent-teal);
  border-radius: 1px;
  transition: width 0.32s ease;
}

/* 3D card scene */
.fc-scene {
  perspective: 1200px;
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 300px;
}

.fc-card {
  width: 100%;
  height: clamp(300px, 44vh, 420px);
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.44s cubic-bezier(0.4, 0, 0.2, 1);
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  user-select: none;
}

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

.fc-face {
  position: absolute;
  inset: 0;
  border-radius: 14px;
  border: 1px solid var(--border-strong);
  background: var(--surface);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 3rem 2.75rem 2.25rem;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  overflow: hidden;
}

.fc-face-back { transform: rotateY(180deg); }

.fc-face-label {
  font-family: var(--mono);
  font-size: 0.55rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--hint);
  position: absolute;
  top: 1rem;
  left: 1.5rem;
}

.fc-card-counter {
  font-family: var(--mono);
  font-size: 0.55rem;
  letter-spacing: 0.06em;
  color: var(--hint);
  position: absolute;
  top: 1rem;
  right: 1.5rem;
}

.fc-concept {
  font-family: var(--sans);
  font-size: clamp(1.15rem, 3.5vw, 1.45rem);
  font-weight: 500;
  color: var(--text);
  text-align: center;
  line-height: 1.55;
  margin: 0;
}

.fc-formula {
  font-size: 1.05rem;
  color: var(--text);
  text-align: center;
  line-height: 1.7;
}

.fc-desc {
  font-family: var(--mono);
  font-size: 0.6rem;
  color: var(--hint);
  text-align: center;
  margin: 0.85rem 0 0;
  line-height: 1.7;
  letter-spacing: 0.01em;
}

/* Bottom controls */
.fc-bottom {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 1.5rem;
  gap: 1rem;
}

.fc-hint {
  font-family: var(--mono);
  font-size: 0.6rem;
  letter-spacing: 0.05em;
  color: var(--hint);
  margin: 0;
  flex: 1;
}

.fc-nav {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  flex-shrink: 0;
}

.fc-btn {
  width: 2.5rem;
  height: 2.5rem;
  background: none;
  border: 1px solid var(--border-strong);
  border-radius: 6px;
  color: var(--muted);
  font-size: 1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: border-color 0.15s, color 0.15s;
}
.fc-btn:hover:not(:disabled) { border-color: var(--accent-teal); color: var(--accent-teal); }
.fc-btn:disabled { opacity: 0.22; cursor: default; }
.fc-shuffle-btn.active { border-color: var(--accent-purple); color: var(--accent-purple); }
.fc-star-btn.active { border-color: var(--accent-amber); color: var(--accent-amber); }
.fc-filter-btn[data-mode="starred"].active { background: var(--accent-amber); border-color: var(--accent-amber); }

.fc-empty {
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--muted);
  text-align: center;
  padding: 2rem 0;
}

@media (max-width: 600px) {
  .fc-wrap {
    padding: 1.5rem 1.1rem 2.5rem;
  }
  .fc-scene {
    min-height: 260px;
  }
  .fc-card {
    height: clamp(260px, 50vh, 380px);
  }
  .fc-face {
    padding: 2.5rem 1.75rem 1.75rem;
    border-radius: 12px;
  }
  .fc-btn {
    width: 2.75rem;
    height: 2.75rem;
  }
  .fc-bottom {
    margin-top: 1.25rem;
  }
}