:root {
  --bg: #efefef;
  --text: #101010;
  --line: #7f7f7f;
  --line-soft: #a7a7a7;
  --ok: #1f9d55;
  --bad: #d64545;
  --primary: #1f1f1f;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Noto Sans SC", sans-serif;
  background: var(--bg);
  color: var(--text);
  padding: 42px 16px 64px;
}

.app {
  width: min(980px, 100%);
  margin: 0 auto;
  display: grid;
  gap: 18px;
}

.hero {
  position: relative;
  isolation: isolate;
  text-align: center;
}

.hero::before {
  content: "";
  position: absolute;
  left: 50%;
  top: -8px;
  transform: translateX(-50%);
  width: 100vw;
  height: 122px;
  background: rgba(255, 255, 255, 0.95);
  filter: blur(30px);
  z-index: -1;
  pointer-events: none;
}

.hero h1 {
  margin: 0;
  font-family: system-ui, sans-serif;
  font-size: clamp(2.8rem, 5vw, 4rem);
  line-height: 1;
  color: #111111;
}

.hero p {
  margin: 10px 0 0;
  font-size: clamp(1.3rem, 2.1vw, 1.9rem);
  font-weight: 600;
}

.panel {
  background: transparent;
  border: 0;
  padding: 0;
}

.text-panel {
  display: block;
}

.text-stream {
  max-height: 440px;
  overflow-y: auto;
  display: grid;
  gap: 10px;
  padding-right: 4px;
  scrollbar-width: none;
  -ms-overflow-style: none;
}

.text-stream::-webkit-scrollbar {
  display: none;
}

.history-feed {
  display: grid;
  gap: 10px;
}

.history-hint {
  margin: -2px 0 -2px;
  text-align: center;
  font-size: 2rem;
  font-weight: 700;
}

.history-item {
  border: 2px solid var(--line);
  border-radius: 28px;
  background: rgba(255, 255, 255, 0.4);
  padding: 14px 22px 18px;
  opacity: 0;
  transform: translateY(24px);
}

.history-item.show {
  animation: history-rise 0.62s ease forwards;
}

.history-item .source-order,
.history-item .source-text,
.history-item .pair-unit {
  opacity: 0.38;
}

.history-item .target-text {
  border: 0;
  border-radius: 0;
  padding: 0;
  min-height: auto;
}

.target-text {
  border: 2px solid var(--line);
  border-radius: 28px;
  background: transparent;
  padding: 14px 22px 18px;
  min-height: 140px;
}

.target-text.enter {
  animation: target-fade 0.5s ease;
}

.source-order {
  margin: 0;
  font-size: 1.9rem;
  font-weight: 700;
  line-height: 1.2;
}

.source-text {
  margin: 2px 0 8px;
  font-size: 1.95rem;
  line-height: 1.28;
}

.pair-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 10px;
}

.pair-unit {
  min-width: 96px;
  border: 2px solid var(--line-soft);
  border-radius: 10px;
  background: transparent;
  padding: 4px 10px 5px;
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  line-height: 1;
}

.hanzi-char {
  font-size: clamp(2.25rem, 3.2vw, 2.7rem);
  font-weight: 700;
}

.pinyin-char {
  margin-top: 3px;
  font-size: 1.45rem;
  letter-spacing: 0.5px;
  text-transform: lowercase;
  color: #8a8a8a;
}

.pinyin-letter {
  display: inline-block;
}

.pinyin-letter.correct {
  color: var(--ok);
}

.pinyin-letter.wrong {
  color: var(--bad);
  text-decoration: underline;
  text-underline-offset: 4px;
}

.pinyin-letter.current {
  background: rgba(0, 0, 0, 0.1);
  border-radius: 2px;
}

.pair-unit.current {
  border-color: var(--primary);
}

.pair-unit.wrong {
  border-color: var(--bad);
}

.input-panel {
  border: 2px solid var(--line);
  border-radius: 28px;
  padding: 16px 24px;
  display: grid;
  gap: 8px;
}

.input-panel label {
  font-size: 2rem;
  font-weight: 700;
}

textarea {
  width: 100%;
  resize: vertical;
  border: 0;
  background: transparent;
  border-radius: 12px;
  padding: 0;
  font: inherit;
  font-size: 1.8rem;
  line-height: 1.4;
  min-height: 88px;
}

textarea:focus {
  outline: none;
}

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

.stat-card {
  border: 1px solid rgba(0, 0, 0, 0.25);
  border-radius: 12px;
  padding: 10px;
  text-align: center;
  background: rgba(255, 255, 255, 0.4);
}

.stat-card span {
  display: block;
  font-size: 0.95rem;
  opacity: 0.7;
}

.stat-card strong {
  display: block;
  margin-top: 3px;
  font-size: 1.45rem;
}

.actions {
  display: flex;
  justify-content: center;
}

button {
  border: 1px solid #202020;
  background: transparent;
  color: #202020;
  padding: 10px 16px;
  border-radius: 999px;
  font: inherit;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
}

@keyframes history-rise {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes target-fade {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (max-width: 900px) {
  .hero p {
    font-size: 1.2rem;
  }

  .source-order,
  .source-text,
  .pinyin-char,
  .input-panel label,
  textarea,
  .history-hint {
    font-size: 1.35rem;
  }

  .hanzi-char {
    font-size: 1.8rem;
  }

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

  .text-stream {
    max-height: 360px;
  }
}

@media (max-width: 560px) {
  body {
    padding: 20px 12px 36px;
  }

  .app {
    gap: 12px;
  }

  .target-text,
  .input-panel,
  .history-item {
    border-radius: 18px;
    padding: 12px;
  }

  .pair-unit {
    min-width: 74px;
    padding: 4px 6px;
  }

  .stats {
    grid-template-columns: 1fr;
  }
}