:root {
  --bg: #ffffff;
  --bg-card: #f5f5f5;
  --bg-input: #fafafa;
  --border: #e0e0e0;
  --text: #1a1a1a;
  --text-secondary: #666666;
  --text-muted: #999999;
  --accent: #000000;
  --accent-text: #ffffff;
  --tone-track: #d0d0d0;
  --tone-dot: #b0b0b0;
  --tone-dot-active: #333333;
  --tone-label: #999999;
  --tone-label-active: #1a1a1a;
  --result-border: #e0e0e0;
  --copy-border: #cccccc;
  --success: #22c55e;
}
[data-theme="dark"] {
  --bg: #0a0a0a;
  --bg-card: #141414;
  --bg-input: #0f0f0f;
  --border: #2a2a2a;
  --text: #e5e5e5;
  --text-secondary: #a0a0a0;
  --text-muted: #525252;
  --accent: #ffffff;
  --accent-text: #000000;
  --tone-track: #3a3a3a;
  --tone-dot: #555555;
  --tone-dot-active: #e5e5e5;
  --tone-label: #525252;
  --tone-label-active: #e5e5e5;
  --result-border: #2a2a2a;
  --copy-border: #333333;
  --success: #4ade80;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  padding: 24px 16px;
  max-width: 680px;
  margin: 0 auto;
  transition: background 0.2s, color 0.2s;
}
.top-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 24px;
}
.lang-bar {
  display: flex;
  gap: 6px;
}
.lang-bar button, .theme-btn {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-secondary);
  padding: 4px 12px;
  font-size: 12px;
  cursor: pointer;
  transition: all 0.15s;
}
.lang-bar button.active {
  background: var(--accent);
  color: var(--accent-text);
  border-color: var(--accent);
}
.theme-btn {
  width: 32px;
  height: 32px;
  padding: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}
.mode-bar {
  display: flex;
  gap: 8px;
  margin-bottom: 28px;
}
.mode-tab {
  flex: 1;
  text-align: center;
  padding: 14px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 15px;
  font-weight: 500;
  transition: all 0.15s;
}
.mode-tab.active {
  background: var(--accent);
  color: var(--accent-text);
  border-color: var(--accent);
}
.section { display: none; }
.section.active { display: block; }
.label {
  font-size: 11px;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 8px;
  font-weight: 600;
}
.sublabel {
  font-size: 11px;
  color: var(--text-muted);
  margin-bottom: 6px;
}

/* Tone Slider */
.tone-wrap { margin-bottom: 24px; }
.tone-slider {
  position: relative;
  padding: 22px 0 4px;
  user-select: none;
  margin: 0 4px;
}
.tone-track {
  position: absolute;
  top: 29px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--tone-track);
}
.tone-dots {
  display: flex;
  justify-content: space-between;
  position: relative;
  padding: 0;
}
.tone-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  cursor: pointer;
  position: relative;
  flex: 1;
}
.tone-item:first-child { align-items: flex-start; }
.tone-item:last-child { align-items: flex-end; }
.tone-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--tone-dot);
  transition: all 0.2s ease;
  position: relative;
  z-index: 1;
}
.tone-item.active .tone-dot {
  background: var(--tone-dot-active);
  transform: scale(1.35);
}
.tone-label {
  position: absolute;
  top: -20px;
  font-size: 11px;
  color: var(--tone-label);
  white-space: nowrap;
  transition: color 0.2s ease;
  font-weight: 500;
}
.tone-item:first-child .tone-label { left: 0; transform: none; }
.tone-item:last-child .tone-label { right: 0; transform: none; }
.tone-item:not(:first-child):not(:last-child) .tone-label {
  left: 50%;
  transform: translateX(-50%);
}
.tone-item.active .tone-label {
  color: var(--tone-label-active);
  font-weight: 600;
}

textarea {
  width: 100%;
  background: var(--bg-input);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 12px;
  font-size: 14px;
  font-family: inherit;
  resize: vertical;
  outline: none;
  line-height: 1.5;
  transition: border-color 0.15s;
}
textarea:focus { border-color: var(--text-muted); }
textarea::placeholder { color: var(--text-muted); }
.box-small { min-height: 80px; margin-bottom: 4px; }
.box-large { min-height: 160px; margin-bottom: 4px; }
.btn {
  width: 100%;
  padding: 14px;
  background: var(--accent);
  color: var(--accent-text);
  border: none;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: opacity 0.15s;
}
.btn:hover { opacity: 0.85; }
.btn:active { transform: scale(0.998); }
.btn-secondary {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border);
  padding: 4px 10px;
  font-size: 11px;
  cursor: pointer;
  transition: all 0.15s;
}
.btn-secondary:hover {
  border-color: var(--text-muted);
  color: var(--text);
}
.input-actions {
  display: flex;
  justify-content: flex-end;
  gap: 6px;
  margin-bottom: 12px;
}
.loading {
  display: none;
  text-align: center;
  padding: 32px 16px;
}
.loading.show { display: block; }
.spinner-wrap {
  display: none;
  justify-content: center;
  align-items: center;
  padding: 16px;
}
.spinner-wrap.show { display: flex; }
.spinner-wrap img {
  width: 64px;
  height: 64px;
}
.loading-text {
  color: var(--text-muted);
  font-size: 13px;
  margin-top: 8px;
}
.result-box {
  display: none;
  margin-top: 24px;
  background: var(--bg-card);
  border: 1px solid var(--result-border);
  padding: 16px;
}
.result-box.show { display: block; }
.result-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--result-border);
}
.result-title {
  font-size: 11px;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-weight: 600;
}
.copy-btn {
  background: transparent;
  border: 1px solid var(--copy-border);
  color: var(--text-secondary);
  padding: 4px 10px;
  font-size: 12px;
  cursor: pointer;
  transition: all 0.15s;
}
.copy-btn:hover { border-color: var(--text-muted); color: var(--text); }
.result-body {
  white-space: pre-wrap;
  font-size: 14px;
  line-height: 1.7;
  color: var(--text);
}
.result-body strong { color: var(--text); font-weight: 700; }
.result-body ul { margin: 8px 0; padding-left: 20px; }
.result-body li { margin: 4px 0; }
.grammar-section { margin-bottom: 16px; }
.grammar-section:last-child { margin-bottom: 0; }
.grammar-section-title {
  font-size: 11px;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-weight: 600;
  margin-bottom: 6px;
}
.grammar-corrected {
  font-size: 14px;
  line-height: 1.7;
  color: var(--text);
  padding: 8px 0;
}
.grammar-issues {
  font-size: 14px;
  line-height: 1.7;
  color: var(--text-secondary);
}
.no-issues {
  color: var(--success);
  font-weight: 600;
}
.footer-section {
  margin-top: 40px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}
.accordion-item { margin-bottom: 12px; }
.accordion-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
  padding: 8px 0;
}
.accordion-header:hover .sublabel { color: var(--text); }
.accordion-toggle {
  font-size: 11px;
  color: var(--text-muted);
  background: none;
  border: 1px solid var(--border);
  padding: 2px 8px;
  cursor: pointer;
  transition: all 0.15s;
  user-select: none;
  display: inline-block;
}
.accordion-toggle:hover {
  border-color: var(--text-muted);
  color: var(--text);
}
.accordion-content {
  display: none;
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.6;
  padding-bottom: 8px;
}
.accordion-content.show { display: block; }
.footer-text a {
  color: var(--text-secondary);
  text-decoration: underline;
}
.footer-text a:hover { color: var(--text); }