:root {
  --bg: #f9fafb;
  --fg: #111827;
  --muted: #6b7280;
  --card-bg: #ffffff;
  --border: #e5e7eb;
  --yes: #16a34a;
  --no: #dc2626;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f172a;
    --fg: #f1f5f9;
    --muted: #94a3b8;
    --card-bg: #1e293b;
    --border: #334155;
  }
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html, body {
  height: 100%;
  background: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI",
               "Hiragino Sans", "Noto Sans JP", "Yu Gothic", Roboto, sans-serif;
  -webkit-font-smoothing: antialiased;
  -webkit-tap-highlight-color: transparent;
  overscroll-behavior: none;
}

.screen {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  min-height: 100dvh;
  padding: 20px;
  padding-top: max(20px, env(safe-area-inset-top));
  padding-bottom: max(20px, env(safe-area-inset-bottom));
}

.hidden { display: none !important; }

header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 24px;
  min-height: 40px;
}

h1 { font-size: 1.5rem; font-weight: 600; }

/* --- Уроки --- */
.lessons-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.lesson-btn {
  display: block;
  width: 100%;
  padding: 20px;
  background: var(--card-bg);
  color: var(--fg);
  border: 1px solid var(--border);
  border-radius: 14px;
  font-size: 1.1rem;
  font-weight: 500;
  text-align: left;
  font-family: inherit;
  cursor: pointer;
  transition: transform 0.1s;
}
.lesson-btn:active { transform: scale(0.98); }

.lesson-count {
  display: block;
  margin-top: 4px;
  font-size: 0.85rem;
  font-weight: 400;
  color: var(--muted);
}

/* --- Сессия --- */
.progress {
  font-size: 0.95rem;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}

.btn-text {
  background: none;
  border: none;
  color: var(--fg);
  font-size: 1rem;
  font-family: inherit;
  cursor: pointer;
  padding: 8px;
  margin-left: -8px;
}

.card-area {
  flex: 1;
  display: flex;
  align-items: stretch;          /* растягиваем .card по высоте */
  justify-content: center;
  perspective: 1400px;
  padding: 12px 0;
  min-height: 0;                 /* иначе flex-контейнер не сжимается */
}

.card {
  width: 100%;
  max-width: 480px;
  min-height: 360px;             /* страховка, если родитель почему-то схлопнется */
  position: relative;
  cursor: pointer;
}

.card-inner {
  position: absolute;            /* ключевое: заполняет .card целиком */
  inset: 0;
  transition: transform 0.5s cubic-bezier(0.4, 0, 0.2, 1);
  transform-style: preserve-3d;
}
.card.flipped .card-inner { transform: rotateY(180deg); }

.card-face {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 28px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 20px;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  text-align: center;
  box-shadow: 0 4px 24px rgba(0, 0, 0, 0.05);
}
.card-back { transform: rotateY(180deg); }

.card-text {
  font-size: clamp(2rem, 11vw, 3.6rem);
  line-height: 1.25;
  font-weight: 500;
  word-break: break-word;
}

.card-back .card-text {
  font-size: clamp(1.8rem, 8vw, 2.4rem);
  font-weight: 500;
}

.card-reading {
  margin-top: 18px;
  font-size: clamp(1.15rem, 5vw, 1.4rem);
  color: var(--muted);
}

/* --- Кнопки --- */
.actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 8px;
}

.btn {
  padding: 18px;
  border: none;
  border-radius: 14px;
  font-size: 1.05rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  color: #fff;
  transition: transform 0.1s, opacity 0.15s;
}
.btn:active { transform: scale(0.97); opacity: 0.9; }

.btn-yes { background: var(--yes); }
.btn-no  { background: var(--no);  }

/* --- Завершение --- */
#done-screen {
  align-items: center;
  justify-content: center;
  text-align: center;
  gap: 14px;
}
#done-screen h2 { font-size: 1.6rem; font-weight: 600; }
#done-screen p { color: var(--muted); font-size: 1.05rem; }
#done-screen .btn { margin-top: 20px; padding: 16px 32px; }