/* 基础重置 */
html, body, main, header, footer {
  padding: 0;
  margin: 0;
}

/* ===== Material 3 紫色系主题变量 ===== */
:root {
  --md-primary: #6750A4;
  --md-on-primary: #FFFFFF;
  --md-primary-container: #EADDFF;
  --md-on-primary-container: #21005D;
  --md-surface: #FFFBFE;
  --md-surface-variant: #E7E0EC;
  --md-on-surface: #1C1B1F;
  --md-on-surface-variant: #49454F;
  --md-outline: #79747E;
  --md-error: #B3261E;
  --md-error-container: #F9DEDC;
  --md-on-error-container: #410E0B;
  --md-radius: 12px;
  --md-radius-sm: 8px;
}

body {
  font-family: 'Roboto', 'Noto Sans SC', sans-serif;
  background: var(--md-surface);
  color: var(--md-on-surface);
  line-height: 1.6;
}

/* ===== Header ===== */
header {
  display: flex;
  justify-content: center;
  padding: 16px 16px 0;
}

/* ===== Main ===== */
main {
  max-width: 720px;
  margin: 0 auto;
  padding: 24px 16px 48px;
}

/* ===== App 区域 ===== */
#app {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

#app > section {
  background: var(--md-surface);
  border: 1px solid var(--md-outline);
  border-radius: var(--md-radius);
  padding: 24px;
}

#app > section h2 {
  margin: 0 0 16px;
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--md-on-primary-container);
  display: flex;
  align-items: center;
  gap: 8px;
}

#app > section h2::before {
  content: '';
  display: inline-block;
  width: 4px;
  height: 20px;
  background: var(--md-primary);
  border-radius: 2px;
}

/* ===== 输入行 ===== */
.input-row {
  display: flex;
  gap: 8px;
  align-items: center;
}

.input-row input {
  flex: 1;
  min-width: 0;
  height: 48px;
  padding: 0 16px;
  border: 2px solid var(--md-outline);
  border-radius: var(--md-radius-sm);
  font-size: 1rem;
  background: var(--md-surface);
  color: var(--md-on-surface);
  outline: none;
  transition: border-color 0.2s;
  box-sizing: border-box;
  touch-action: manipulation;
}

.input-row input:focus {
  border-color: var(--md-primary);
}

.input-row input.error {
  border-color: var(--md-error);
}

/* ===== 转换按钮 ===== */
.convert-btn {
  height: 48px;
  min-width: 44px;
  padding: 0 20px;
  border: none;
  border-radius: 100px;
  background: var(--md-primary);
  color: var(--md-on-primary);
  font-size: 0.95rem;
  font-weight: 500;
  cursor: pointer;
  white-space: nowrap;
  touch-action: manipulation;
  transition: background 0.2s, box-shadow 0.2s;
  user-select: none;
}

.convert-btn:hover {
  background: #5A3E9A;
  box-shadow: 0 2px 8px rgba(103, 80, 164, 0.4);
}

.convert-btn:active {
  background: #4E338D;
}

/* ===== 错误提示 ===== */
.error-msg {
  min-height: 20px;
  font-size: 0.85rem;
  color: var(--md-error);
  margin-top: 6px;
  padding-left: 4px;
  display: none;
}

.error-msg.visible {
  display: block;
}

/* ===== 结果区域 ===== */
.result-area {
  display: none;
  align-items: center;
  gap: 12px;
  margin-top: 16px;
  padding: 16px 20px;
  background: var(--md-primary-container);
  border-radius: var(--md-radius-sm);
  min-height: 52px;
  box-sizing: border-box;
}

.result-area.visible {
  display: flex;
}

.result-area .result-text {
  flex: 1;
  font-size: 1.15rem;
  font-weight: 500;
  color: var(--md-on-primary-container);
  word-break: break-all;
}

/* ===== 复制按钮 ===== */
.copy-btn {
  width: 44px;
  height: 44px;
  min-width: 44px;
  min-height: 44px;
  border: none;
  border-radius: 50%;
  background: var(--md-primary);
  color: var(--md-on-primary);
  font-size: 1.1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  touch-action: manipulation;
  transition: background 0.2s;
  user-select: none;
  flex-shrink: 0;
}

.copy-btn:hover {
  background: #5A3E9A;
}

.copy-btn:active {
  background: #4E338D;
}

.copy-btn.copied {
  background: #2E7D32;
}

/* ===== 约分过程 ===== */
.process-area {
  display: none;
  margin-top: 8px;
  padding: 12px 16px;
  font-size: 0.9rem;
  color: var(--md-on-surface-variant);
  background: var(--md-surface-variant);
  border-radius: var(--md-radius-sm);
  line-height: 1.8;
}

.process-area.visible {
  display: block;
}

.process-area .arrow {
  color: var(--md-primary);
  font-weight: 600;
  margin: 0 4px;
}

/* ===== 扩展区域 ===== */
#__fork {
  text-align: center;
  margin: 32px 0;
}

#__fork button {
  height: 44px;
  min-width: 44px;
  padding: 0 28px;
  border: 2px solid var(--md-primary);
  border-radius: 100px;
  background: transparent;
  color: var(--md-primary);
  font-size: 0.95rem;
  font-weight: 500;
  cursor: pointer;
  touch-action: manipulation;
  transition: background 0.2s, color 0.2s;
  user-select: none;
}

#__fork button:hover {
  background: var(--md-primary-container);
  color: var(--md-on-primary-container);
}

#features, #scenarios, #FAQ {
  margin: 24px 0;
  padding: 24px;
  background: var(--md-surface-variant);
  border-radius: var(--md-radius);
}

#features h2, #scenarios h2, #FAQ h2 {
  margin: 0 0 12px;
  font-size: 1.15rem;
  color: var(--md-on-primary-container);
}

#features p {
  margin: 0;
  font-size: 0.95rem;
  color: var(--md-on-surface-variant);
}

#scenarios ul {
  margin: 0;
  padding-left: 20px;
}

#scenarios li {
  margin-bottom: 8px;
  font-size: 0.95rem;
  color: var(--md-on-surface-variant);
}

#FAQ dl {
  margin: 0;
}

#FAQ dt {
  font-weight: 600;
  margin-top: 16px;
  margin-bottom: 4px;
  color: var(--md-on-surface);
  font-size: 0.95rem;
}

#FAQ dt:first-child {
  margin-top: 0;
}

#FAQ dd {
  margin: 0 0 0 0;
  font-size: 0.9rem;
  color: var(--md-on-surface-variant);
}

/* ===== Footer ===== */
footer {
  text-align: center;
  padding: 24px 16px;
  font-size: 0.85rem;
  color: var(--md-on-surface-variant);
}

footer a {
  color: var(--md-primary);
  text-decoration: none;
}

footer a:hover {
  text-decoration: underline;
}

/* ===== 响应式 ===== */
@media (max-width: 480px) {
  main {
    padding: 16px 12px 40px;
  }

  #app > section {
    padding: 16px;
  }

  .input-row {
    flex-wrap: wrap;
  }

  .input-row input {
    min-width: 100%;
  }

  .convert-btn {
    width: 100%;
  }

  .result-area {
    flex-wrap: wrap;
  }

  .result-area .result-text {
    min-width: 0;
  }

  #features, #scenarios, #FAQ {
    padding: 16px;
  }
}