html, body, main, header, footer {
  padding: 0;
  margin: 0;
}

/* Material 3 紫色系主题 */
:root {
  --md-primary: #6750A4;
  --md-on-primary: #FFFFFF;
  --md-primary-container: #EADDFF;
  --md-on-primary-container: #21005D;
  --md-secondary-container: #E8DEF8;
  --md-on-secondary-container: #1D192B;
  --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;
  --md-elevation-1: 0 1px 3px rgba(0,0,0,0.12), 0 1px 2px rgba(0,0,0,0.08);
  --md-elevation-2: 0 3px 6px rgba(0,0,0,0.15), 0 2px 4px rgba(0,0,0,0.10);
}

body {
  font-family: "Roboto", "Noto Sans SC", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background-color: var(--md-surface);
  color: var(--md-on-surface);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

main {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 16px;
}

#app {
  width: 100%;
  max-width: 480px;
  background: var(--md-surface);
  border-radius: 16px;
  padding: 24px 20px;
}

#app h1 {
  font-size: 1.75rem;
  font-weight: 600;
  color: var(--md-on-surface);
  text-align: center;
  margin: 0 0 20px 0;
  letter-spacing: -0.02em;
}

/* Tab 切换栏 */
#tab-bar {
  display: flex;
  gap: 4px;
  background: var(--md-surface-variant);
  border-radius: var(--md-radius);
  padding: 4px;
  margin-bottom: 20px;
}

.tab-btn {
  flex: 1;
  padding: 10px 8px;
  border: none;
  border-radius: 10px;
  background: transparent;
  color: var(--md-on-surface-variant);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s ease;
  min-height: 44px;
  white-space: nowrap;
}

.tab-btn.active {
  background: var(--md-primary-container);
  color: var(--md-on-primary-container);
  font-weight: 600;
  box-shadow: var(--md-elevation-1);
}

.tab-btn:hover:not(.active) {
  background: rgba(103, 80, 164, 0.08);
}

/* 输入区 */
#number-input-wrapper {
  position: relative;
  display: flex;
  align-items: center;
  margin-bottom: 16px;
}

#number-input {
  width: 100%;
  padding: 14px 44px 14px 16px;
  border: 2px solid var(--md-outline);
  border-radius: var(--md-radius-sm);
  font-size: 1.1rem;
  background: var(--md-surface);
  color: var(--md-on-surface);
  outline: none;
  transition: border-color 0.2s ease;
  box-sizing: border-box;
}

#number-input:focus {
  border-color: var(--md-primary);
}

#number-input::placeholder {
  color: var(--md-on-surface-variant);
  opacity: 0.6;
}

.clear-btn {
  position: absolute;
  right: 8px;
  top: 50%;
  transform: translateY(-50%);
  width: 36px;
  height: 36px;
  min-width: 44px;
  min-height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: none;
  background: transparent;
  color: var(--md-on-surface-variant);
  font-size: 1rem;
  cursor: pointer;
  border-radius: 50%;
  transition: background 0.2s ease;
  padding: 0;
}

.clear-btn:hover {
  background: rgba(103, 80, 164, 0.08);
}

/* N 输入区 */
#n-input-area {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 16px;
}

#n-input-area label {
  font-size: 0.95rem;
  color: var(--md-on-surface-variant);
  font-weight: 500;
  white-space: nowrap;
}

#n-input {
  flex: 1;
  padding: 12px 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 ease;
  box-sizing: border-box;
}

#n-input:focus {
  border-color: var(--md-primary);
}

/* 精度选择区 */
#precision-area {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 16px;
}

#precision-area label {
  font-size: 0.95rem;
  color: var(--md-on-surface-variant);
  font-weight: 500;
  white-space: nowrap;
}

#precision-select {
  flex: 1;
  padding: 12px 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;
  cursor: pointer;
  transition: border-color 0.2s ease;
  box-sizing: border-box;
  min-height: 44px;
}

#precision-select:focus {
  border-color: var(--md-primary);
}

/* 计算按钮 */
#calculate-btn {
  width: 100%;
  padding: 14px;
  border: none;
  border-radius: 28px;
  background: var(--md-primary);
  color: var(--md-on-primary);
  font-size: 1.1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  min-height: 44px;
  box-shadow: var(--md-elevation-1);
}

#calculate-btn:hover {
  box-shadow: var(--md-elevation-2);
  filter: brightness(1.1);
}

#calculate-btn:active {
  filter: brightness(0.95);
  transform: scale(0.98);
}

/* 结果展示区 */
#result-area {
  margin-top: 24px;
  padding: 20px;
  background: var(--md-primary-container);
  border-radius: var(--md-radius);
  text-align: center;
  min-height: 60px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  word-break: break-all;
  overflow-wrap: break-word;
}

#result-expression {
  font-size: 0.95rem;
  color: var(--md-on-primary-container);
  opacity: 0.8;
  margin-bottom: 8px;
  word-break: break-all;
}

#result-value {
  font-size: 2rem;
  font-weight: 700;
  color: var(--md-on-primary-container);
  word-break: break-all;
  line-height: 1.3;
}

#result-area.error {
  background: var(--md-error-container);
}

#result-area.error #result-expression {
  color: var(--md-on-error-container);
  opacity: 1;
}

#result-area.error #result-value {
  display: none;
}

/* Fork 按钮 */
#__fork {
  text-align: center;
  margin: 24px 0;
}

#__fork button {
  padding: 12px 28px;
  border: 2px solid var(--md-primary);
  border-radius: 28px;
  background: transparent;
  color: var(--md-primary);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  min-height: 44px;
}

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

/* 扩展内容区 */
#features,
#scenarios,
#FAQ {
  width: 100%;
  max-width: 600px;
  margin: 0 auto 32px;
  padding: 0 16px;
  box-sizing: border-box;
}

#features h2,
#scenarios h2,
#FAQ h2 {
  font-size: 1.3rem;
  font-weight: 600;
  color: var(--md-on-surface);
  margin: 0 0 12px 0;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--md-primary-container);
}

#features p {
  font-size: 0.95rem;
  color: var(--md-on-surface-variant);
  line-height: 1.7;
  margin: 0;
}

#scenarios ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

#scenarios li {
  font-size: 0.95rem;
  color: var(--md-on-surface-variant);
  line-height: 1.6;
  padding: 6px 0;
  border-bottom: 1px solid var(--md-surface-variant);
}

#scenarios li:last-child {
  border-bottom: none;
}

#scenarios li strong {
  color: var(--md-on-surface);
}

#FAQ dl {
  margin: 0;
}

#FAQ dt {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--md-on-surface);
  margin-top: 12px;
}

#FAQ dd {
  font-size: 0.9rem;
  color: var(--md-on-surface-variant);
  line-height: 1.6;
  margin: 4px 0 8px 0;
  padding-left: 0;
}

/* Footer */
footer {
  text-align: center;
  padding: 16px;
}

footer .page-info {
  font-size: 0.8rem;
  color: var(--md-on-surface-variant);
}

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

footer .page-info a:hover {
  text-decoration: underline;
}

/* Small screen optimizations */
@media (max-width: 480px) {
  #app {
    padding: 16px 12px;
  }

  #app h1 {
    font-size: 1.5rem;
  }

  .tab-btn {
    font-size: 0.8rem;
    padding: 8px 4px;
  }

  #result-value {
    font-size: 1.6rem;
  }
}