:root {
  color-scheme: light;
  --bg: #f7f9fc;
  --ink: #172033;
  --muted: #667085;
  --line: #d9e0ea;
  --panel: #ffffff;
  --soft: #eef3f8;
  --accent: #256f8f;
  --accent-strong: #144f66;
  --good: #16805c;
  --good-soft: #e5f6ef;
  --review: #c84f40;
  --review-soft: #fdecea;
  --memory: #7862b8;
  --memory-soft: #f0edfb;
  --shadow: 0 24px 60px rgba(23, 32, 51, 0.14);
}

* {
  box-sizing: border-box;
}

html {
  min-height: 100%;
}

body {
  min-height: 100vh;
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

button {
  font: inherit;
}

.app-shell {
  width: min(1120px, 100%);
  min-height: 100vh;
  margin: 0 auto;
  padding: 28px;
  display: grid;
  grid-template-rows: auto 1fr;
  gap: 28px;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding-bottom: 22px;
  border-bottom: 1px solid var(--line);
}

.brand {
  display: flex;
  align-items: center;
  gap: 14px;
  min-width: 0;
}

.brand-mark {
  width: 48px;
  height: 48px;
  display: grid;
  place-items: center;
  border-radius: 8px;
  background: var(--ink);
  color: #ffffff;
  font-weight: 800;
  letter-spacing: 0;
}

.brand h1 {
  margin: 0;
  font-size: 1.55rem;
  line-height: 1.1;
  letter-spacing: 0;
}

.brand p {
  margin: 4px 0 0;
  color: var(--muted);
  font-size: 0.94rem;
}

.top-actions {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 10px;
  flex-wrap: wrap;
}

.mode-switch {
  display: inline-grid;
  grid-template-columns: 1fr 1fr;
  gap: 4px;
  padding: 4px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--soft);
}

.mode-button,
.icon-button,
.primary-button,
.decision-button {
  border: 0;
  cursor: pointer;
  transition: transform 160ms ease, background 160ms ease, color 160ms ease, border-color 160ms ease, box-shadow 160ms ease;
}

.mode-button {
  min-width: 92px;
  min-height: 38px;
  padding: 0 14px;
  border-radius: 6px;
  background: transparent;
  color: var(--muted);
  font-weight: 700;
}

.mode-button.is-active {
  background: #ffffff;
  color: var(--ink);
  box-shadow: 0 2px 10px rgba(23, 32, 51, 0.08);
}

.icon-button {
  width: 48px;
  height: 48px;
  display: grid;
  place-items: center;
  border-radius: 8px;
  border: 1px solid var(--line);
  background: #ffffff;
  color: var(--ink);
  font-size: 1.3rem;
  font-weight: 800;
}

.icon-button:hover,
.mode-button:hover,
.decision-button:hover,
.primary-button:hover {
  transform: translateY(-1px);
}

.study-surface {
  display: grid;
  grid-template-rows: auto minmax(360px, 1fr) auto auto;
  align-items: center;
  gap: 22px;
}

.status-row {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
}

.stat-block {
  min-height: 70px;
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #ffffff;
  display: grid;
  align-content: center;
  gap: 2px;
}

.stat-block strong {
  font-size: 1.45rem;
  line-height: 1;
}

.stat-block span {
  color: var(--muted);
  font-size: 0.88rem;
  font-weight: 700;
}

.stat-block.good {
  background: var(--good-soft);
  border-color: #b7e7d3;
}

.stat-block.review {
  background: var(--review-soft);
  border-color: #f1c0ba;
}

.stat-block.memory {
  background: var(--memory-soft);
  border-color: #d8d0f0;
}

.deck-area {
  position: relative;
  min-height: 360px;
  display: grid;
  place-items: center;
  overflow: hidden;
}

.flashcard {
  width: min(620px, 100%);
  aspect-ratio: 5 / 3.15;
  perspective: 1400px;
  touch-action: pan-y;
  user-select: none;
  outline: none;
  will-change: transform;
  transition: transform 180ms ease;
}

.flashcard.is-dragging {
  transition: none;
}

.flashcard.is-exiting-right {
  transform: translateX(160%) rotate(16deg);
}

.flashcard.is-exiting-left {
  transform: translateX(-160%) rotate(-16deg);
}

.flashcard:focus-visible .card-face {
  box-shadow: 0 0 0 4px rgba(37, 111, 143, 0.22), var(--shadow);
}

.card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transition: transform 280ms ease;
}

.flashcard.is-flipped .card-inner {
  transform: rotateY(180deg);
}

.card-face {
  position: absolute;
  inset: 0;
  border-radius: 8px;
  border: 1px solid var(--line);
  background: var(--panel);
  box-shadow: var(--shadow);
  backface-visibility: hidden;
  display: grid;
  grid-template-rows: auto 1fr;
  padding: 28px;
}

.card-front {
  border-top: 8px solid var(--accent);
}

.card-back {
  border-top: 8px solid var(--good);
  transform: rotateY(180deg);
}

.face-label {
  justify-self: start;
  min-height: 34px;
  padding: 7px 12px;
  border-radius: 999px;
  background: var(--soft);
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 800;
}

.word-wrap {
  min-width: 0;
  display: grid;
  place-items: center;
  align-content: center;
  gap: 16px;
  text-align: center;
}

.card-word {
  max-width: 100%;
  margin: 0;
  font-size: 3.2rem;
  line-height: 1.08;
  font-weight: 850;
  letter-spacing: 0;
  overflow-wrap: anywhere;
}

.card-word.is-long {
  font-size: 2.45rem;
}

.card-word.is-very-long {
  font-size: 1.9rem;
  line-height: 1.16;
}

.card-type {
  margin: 0;
  color: var(--muted);
  font-size: 1.05rem;
  font-weight: 700;
  overflow-wrap: anywhere;
}

.swipe-label {
  position: absolute;
  top: 26px;
  z-index: 2;
  padding: 10px 14px;
  border-radius: 999px;
  font-weight: 850;
  opacity: 0;
  transform: translateY(8px);
  transition: opacity 140ms ease, transform 140ms ease;
}

.swipe-label-left {
  left: 20px;
  background: var(--review-soft);
  color: var(--review);
}

.swipe-label-right {
  right: 20px;
  background: var(--good-soft);
  color: var(--good);
}

.deck-area[data-swipe="left"] .swipe-label-left,
.deck-area[data-swipe="right"] .swipe-label-right {
  opacity: 1;
  transform: translateY(0);
}

.decision-bar {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 12px;
  align-items: center;
}

.decision-button {
  min-height: 54px;
  border-radius: 8px;
  padding: 0 18px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  border: 1px solid transparent;
  font-weight: 850;
}

.decision-button.missed {
  background: var(--review-soft);
  color: #a33c31;
  border-color: #f1c0ba;
}

.decision-button.known {
  background: var(--good-soft);
  color: #116849;
  border-color: #b7e7d3;
}

.decision-button.flip {
  min-width: 132px;
  background: var(--ink);
  color: #ffffff;
}

.decision-button:disabled,
.icon-button:disabled,
.mode-button:disabled {
  cursor: default;
  opacity: 0.55;
  transform: none;
}

.session-complete {
  width: min(520px, 100%);
  padding: 34px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #ffffff;
  box-shadow: var(--shadow);
  text-align: center;
}

.session-complete h2 {
  margin: 0 0 20px;
  font-size: 2rem;
  letter-spacing: 0;
}

.result-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 22px;
}

.result-grid div {
  min-height: 96px;
  display: grid;
  align-content: center;
  gap: 6px;
  border-radius: 8px;
  background: var(--soft);
}

.result-grid strong {
  font-size: 2rem;
  line-height: 1;
}

.result-grid span {
  color: var(--muted);
  font-weight: 800;
}

.primary-button {
  min-height: 48px;
  padding: 0 22px;
  border-radius: 8px;
  background: var(--accent);
  color: #ffffff;
  font-weight: 850;
}

.primary-button:hover {
  background: var(--accent-strong);
}

.error-message {
  margin: 0;
  padding: 12px 14px;
  border-radius: 8px;
  border: 1px solid #f1c0ba;
  background: var(--review-soft);
  color: #8b332a;
  font-weight: 700;
}

@media (max-width: 760px) {
  .app-shell {
    padding: 18px;
    gap: 20px;
  }

  .topbar {
    align-items: flex-start;
    flex-direction: column;
  }

  .top-actions,
  .mode-switch {
    width: 100%;
  }

  .mode-switch {
    flex: 1;
  }

  .mode-button {
    min-width: 0;
  }

  .status-row {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .study-surface {
    grid-template-rows: auto minmax(240px, auto) auto auto;
  }

  .deck-area {
    min-height: 240px;
  }

  .flashcard {
    aspect-ratio: 3 / 2;
  }

  .card-face {
    padding: 18px;
  }

  .card-word {
    font-size: 2.05rem;
  }

  .card-word.is-long {
    font-size: 1.65rem;
  }

  .card-word.is-very-long {
    font-size: 1.25rem;
  }

  .decision-bar {
    grid-template-columns: 1fr 1fr;
  }

  .decision-button.flip {
    grid-column: 1 / -1;
    grid-row: 1;
  }
}

@media (max-width: 420px) {
  .brand h1 {
    font-size: 1.3rem;
  }

  .brand-mark {
    width: 42px;
    height: 42px;
  }

  .stat-block {
    padding: 10px;
  }

  .decision-button {
    padding: 0 12px;
  }
}