:root {
  color-scheme: light;
  --bg: #f4f7fb;
  --card: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --primary: #2563eb;
  --primary-soft: #dbeafe;
  --danger: #dc2626;
  --danger-soft: #fee2e2;
  --border: #e5e7eb;
}

* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: "PingFang SC", "Microsoft YaHei", Arial, sans-serif;
  background: linear-gradient(180deg, #f8fbff 0%, var(--bg) 100%);
  color: var(--text);
}

.tracker-shell {
  max-width: 1280px;
  margin: 0 auto;
  padding: 24px 16px 48px;
}

.tracker-header,
.input-panel,
.stats-panel,
.history-panel {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  box-shadow: 0 8px 24px rgba(15, 23, 42, 0.06);
  padding: 20px;
  margin-bottom: 18px;
}

.tracker-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 16px;
}

.tracker-header h1,
.stats-head h2,
.history-head h2 {
  margin: 0 0 6px;
  font-size: 1.3rem;
}

.tracker-header p,
.stats-head p,
.history-head p {
  margin: 0;
  color: var(--muted);
  line-height: 1.5;
}

.btn {
  border: 0;
  border-radius: 999px;
  padding: 10px 16px;
  font-size: 0.95rem;
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn-primary {
  background: var(--primary);
  color: white;
}

.btn-secondary {
  background: var(--primary-soft);
  color: var(--primary);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.input-panel label {
  display: block;
  font-weight: 600;
  margin-bottom: 8px;
}

textarea {
  width: 100%;
  min-height: 110px;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px 14px;
  resize: vertical;
  font-size: 1rem;
  line-height: 1.6;
}

.input-actions {
  display: flex;
  gap: 10px;
  margin-top: 12px;
}

.stats-list {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.stat-chip {
  padding: 10px 12px;
  border-radius: 999px;
  font-weight: 600;
  color: #111827;
  border: 1px solid transparent;
}

.history-grid {
  display: flex;
  flex-wrap: nowrap;
  gap: 16px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  padding-bottom: 12px;
  margin-top: 12px;
}

.history-column {
  max-width: 280px;
  background: #fbfdff;
  padding: 14px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.history-column-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-weight: 600;
  color: var(--muted);
}

.word-chip-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.word-chip {
  display: block;
  width: 100%;
  border: 1px solid transparent;
  font-size: 0.95rem;
  color: #111827;
  margin-bottom: 10px;
}

.word-chip:last-child {
  margin-bottom: 0;
}

.word-chip.highlight {
  box-shadow: inset 0 0 0 1px rgba(239, 68, 68, 0.18);
}

.history-column-footer {
  margin-top: auto;
  display: flex;
  justify-content: flex-end;
}

.delete-column-btn {
  background: var(--danger-soft);
  color: var(--danger);
  border: 0;
  padding: 8px 10px;
  border-radius: 999px;
  cursor: pointer;
  font-size: 0.9rem;
}

.empty-state {
  color: var(--muted);
  padding: 24px 0;
}

@media (max-width: 768px) {
  .tracker-shell { padding: 16px 12px 32px; }
  .tracker-header { flex-direction: column; }
  .history-grid { display: block; }
}