* {
  box-sizing: border-box;
}

:root {
  font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color-scheme: light dark;

  --success-text: #145c2b;
  --success-strong: #17813b;
  --success-border: #36a35a;
  --success-background: #f1fbf3;
  --success-flash: #87d69d;
  --success-glow-ring: color-mix(in srgb, var(--success-border) 28%, transparent);
  --success-glow-shadow: color-mix(in srgb, var(--success-strong) 24%, transparent);

  --error-text: #8b241b;
  --error-strong: #c0392b;
  --error-border: #d75b50;
  --error-background: #fff4f3;
  --error-flash: #f09a92;

  --on-success: #fff;
}

body {
  margin: 0;
  min-height: 100vh;
  background: Canvas;
  color: CanvasText;
}

button,
input {
  font: inherit;
}

button,
.file-button {
  border: 1px solid color-mix(in srgb, CanvasText 18%, transparent);
  background: color-mix(in srgb, Canvas 92%, CanvasText 8%);
  color: inherit;
  border-radius: 10px;
  padding: 0.7rem 0.95rem;
  cursor: pointer;
}

button:disabled {
  opacity: 0.45;
  cursor: default;
}

.file-button {
  display: inline-flex;
  align-items: center;
}

.file-button input {
  display: none;
}

.app {
  width: min(760px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 2rem 0 3rem;
}

.topbar {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: flex-start;
  margin-bottom: 2rem;
}

h1 {
  margin: 0 0 0.3rem;
  font-size: clamp(1.6rem, 4vw, 2.3rem);
}

.muted {
  margin: 0;
  opacity: 0.65;
}

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  justify-content: flex-end;
}

.trainer-card {
  border: 1px solid color-mix(in srgb, CanvasText 14%, transparent);
  border-radius: 18px;
  padding: 1rem;
  padding-top: 2rem;
  min-height: 150px;
  display: grid;
  align-content: center;
  gap: 1rem;
}

.question {
  text-align: center;
  font-size:1.8rem;
  font-weight: 750;
  line-height: 1.1;
  overflow-wrap: anywhere;
}

.explanation {
  min-height: 1.2rem;
  margin-top: -0.65rem;
  text-align: center;
  font-size: 0.85rem;
  opacity: 0.65;
}

.answer {
  width: min(100%, 430px);
  margin: 0 auto;
  display: block;
  padding: 0.75rem 1rem;
  border-radius: 12px;
  border: 2px solid color-mix(in srgb, CanvasText 18%, transparent);
  background: Canvas;
  color: CanvasText;
  text-align: center;
  font-size: 1.2rem;
  outline: none;
}

.answer:focus {
  border-color: color-mix(in srgb, CanvasText 55%, transparent);
}

.answer.correct {
  border-color: var(--success-strong);
}

.answer.wrong {
  border-color: var(--error-strong);
}

.feedback {
  display: none;
  position: relative;
  margin-bottom: 1rem;
  padding: 1rem 1.25rem;
  border: 2px solid;
  border-radius: 14px;
  font-size: 1.1rem;
  font-weight: 700;
  line-height: 1.4;
  text-align: center;
  overflow-wrap: anywhere;
}

.feedback.correct,
.feedback.wrong {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.9rem;
}

.feedback-icon {
  display: grid;
  flex: 0 0 2rem;
  width: 2rem;
  height: 2rem;
  place-items: center;
  border: 2px solid currentColor;
  border-radius: 50%;
  font-size: 1.35rem;
  line-height: 1;
}

.feedback-content {
  display: grid;
  min-width: 0;
  gap: 0.15rem;
  text-align: left;
}

.feedback-pair {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.55rem;
}

.feedback-arrow {
  opacity: 0.55;
}

.feedback-submitted {
  font-size: 0.85rem;
  font-weight: 500;
  opacity: 0.75;
}

.feedback.correct {
  color: var(--success-text);
  border-color: var(--success-border);
  background: var(--success-background);
}

.feedback.wrong {
  color: var(--error-text);
  border-color: var(--error-border);
  background: var(--error-background);
}

.feedback.correct.flash {
  animation: flash-correct 600ms;
}

.feedback.wrong.flash {
  animation: flash-wrong 600ms;
}

@keyframes flash-correct {
  from {
    background: var(--success-background);
    box-shadow: 0 0 0 0 transparent;
    transform: scale(1);
    animation-timing-function: ease-in;
  }
  5% {
    background: var(--success-flash);
    box-shadow:
      0 0 0 5px var(--success-glow-ring),
      0 8px 24px var(--success-glow-shadow);
    transform: scale(1.018);
    animation-timing-function: linear;
  }
  30% {
    background: var(--success-flash);
    box-shadow:
      0 0 0 5px var(--success-glow-ring),
      0 8px 24px var(--success-glow-shadow);
    transform: scale(1.018);
    animation-timing-function: ease-out;
  }
  to {
    background: var(--success-background);
    box-shadow: 0 0 0 0 transparent;
    transform: scale(1);
  }
}

.feedback.correct.flash .feedback-icon {
  animation: success-icon-pop 800ms;
}

@keyframes success-icon-pop {
  from {
    background: transparent;
    color: var(--success-text);
    transform: scale(0.8);
    animation-timing-function: ease-out;
  }
  5% {
    background: var(--success-strong);
    color: var(--on-success);
    transform: scale(1.25) rotate(-7deg);
    animation-timing-function: ease-in-out;
  }
  30% {
    background: var(--success-strong);
    color: var(--on-success);
    transform: scale(1.1) rotate(0);
    animation-timing-function: ease-out;
  }
  to {
    background: transparent;
    color: var(--success-text);
    transform: scale(1);
  }
}

@keyframes flash-wrong {
  from {
    background: var(--error-background);
    animation-timing-function: ease-in;
  }
  5% {
    background: var(--error-flash);
    animation-timing-function: linear;
  }
  30% {
    background: var(--error-flash);
    animation-timing-function: ease-out;
  }
  to { background: var(--error-background); }
}

.stats {
  margin-top: 1rem;
  display: flex;
  justify-content: center;
  gap: 1.2rem;
  flex-wrap: wrap;
  font-variant-numeric: tabular-nums;
}

.word-stats {
  position: fixed;
  right: 0.75rem;
  bottom: 0.75rem;
  z-index: 10;
  display: grid;
  gap: 0.2rem;
  max-width: calc(100vw - 1.5rem);
  padding: 0.45rem 0.6rem;
  border: 1px solid color-mix(in srgb, CanvasText 12%, transparent);
  border-radius: 8px;
  background: color-mix(in srgb, Canvas 94%, transparent);
  font-size: 0.72rem;
  font-variant-numeric: tabular-nums;
  opacity: 0.55;
  transition: opacity 150ms ease-out;
}

.word-stats:empty {
  display: none;
}

.word-stats:hover {
  opacity: 0.9;
}

.word-stats-row {
  display: flex;
  align-items: baseline;
  gap: 0.45rem;
  white-space: nowrap;
}

.word-stats-label {
  width: 3.3rem;
  opacity: 0.7;
}

.word-stats-row strong {
  max-width: 9rem;
  overflow: hidden;
  text-overflow: ellipsis;
}

.word-stats-correct {
  color: var(--success-strong);
}

.word-stats-wrong {
  color: var(--error-strong);
}

.word-stats-recent {
  min-width: 2.8rem;
  letter-spacing: 0.08em;
  opacity: 0.75;
}

.help {
  margin-top: 2rem;
  opacity: 0.8;
}

.help pre {
  overflow-x: auto;
  padding: 1rem;
  border-radius: 10px;
  background: color-mix(in srgb, Canvas 88%, CanvasText 12%);
}

.csv-download a {
  color: inherit;
  font-weight: 650;
}

@media (max-width: 700px) {
  .topbar {
    flex-direction: column;
  }

  .controls {
    justify-content: flex-start;
  }

  .word-stats {
    position: static;
    width: fit-content;
    margin: 0.75rem 0.75rem 0.75rem auto;
  }
}