:root {
  color-scheme: light dark;
  --easy: #2fa84f;
  --medium: #d99a1b;
  --hard: #d9463f;
  --border: #d0d0d5;
  --bg: #fff;
  --fg: #1a1a1a;
  --muted: #6b6b6f;
  --row-hover: #f4f4f7;
}
@media (prefers-color-scheme: dark) {
  :root {
    --border: #3a3a40;
    --bg: #16161a;
    --fg: #e8e8ea;
    --muted: #9a9aa0;
    --row-hover: #202024;
  }
}

* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--fg);
}

header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  padding: 12px 20px;
}
.header-top { display: flex; align-items: center; justify-content: space-between; gap: 12px; }
h1 { font-size: 1.2rem; margin: 0; }
.header-actions { display: flex; gap: 8px; }
.header-actions button, .import-label {
  font-size: 0.85rem;
  padding: 6px 12px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: transparent;
  color: var(--fg);
  cursor: pointer;
}

.progress-row { display: flex; align-items: center; gap: 10px; margin-top: 10px; }
.progress-bar {
  flex: 1;
  height: 10px;
  background: var(--row-hover);
  border-radius: 6px;
  overflow: hidden;
}
.progress-fill { height: 100%; background: var(--easy); width: 0%; transition: width 0.2s; }
.progress-label { font-size: 0.85rem; color: var(--muted); white-space: nowrap; }

.controls { display: flex; align-items: center; gap: 12px; margin-top: 10px; flex-wrap: wrap; }
#search {
  flex: 1;
  min-width: 160px;
  padding: 6px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--bg);
  color: var(--fg);
}
.diff-filter { display: flex; gap: 6px; }
.diff-btn {
  font-size: 0.8rem;
  padding: 5px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: transparent;
  color: var(--fg);
  cursor: pointer;
}
.diff-btn.active { background: var(--fg); color: var(--bg); }
.filter-select {
  font-size: 0.8rem;
  padding: 5px 8px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--bg);
  color: var(--fg);
}
.hide-completed { font-size: 0.85rem; color: var(--muted); display: flex; align-items: center; gap: 4px; }

main { max-width: 900px; margin: 0 auto; padding: 16px 20px 60px; }

details > summary {
  cursor: pointer;
  list-style: none;
}
details > summary::-webkit-details-marker { display: none; }
details > summary::before { content: "▸"; margin-right: 6px; }
details[open] > summary::before { content: "▾"; }

details.topic {
  border: 1px solid var(--border);
  border-radius: 8px;
  margin-bottom: 10px;
}
details.topic > summary {
  padding: 10px 14px;
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 600;
}
.topic-progress {
  font-weight: 400;
  font-size: 0.8rem;
  color: var(--muted);
  margin-left: auto;
}

details.pattern { padding: 2px 14px 2px 30px; }
details.pattern > summary {
  padding: 6px 0;
  font-size: 0.85rem;
  color: var(--muted);
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 8px;
}
details.pattern[open] > summary { margin-bottom: 2px; }
.pattern-body { padding-left: 12px; }

.analytics {
  max-width: 900px;
  margin: 0 auto 14px;
  padding: 4px 20px;
}
.analytics > summary {
  font-weight: 600;
  padding: 8px 0;
}
.analytics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 12px;
  padding: 4px 0 12px;
}
.analytics-card {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px 12px;
}
.analytics-card-title { font-size: 0.8rem; font-weight: 600; margin-bottom: 8px; }
.analytics-row { display: flex; align-items: center; gap: 8px; margin: 6px 0; font-size: 0.78rem; }
.analytics-label { width: 70px; flex-shrink: 0; color: var(--muted); }
.analytics-count { width: 48px; flex-shrink: 0; text-align: right; color: var(--muted); }
.progress-bar.mini { height: 6px; }

.problem-row {
  display: flex;
  align-items: flex-start;
  gap: 8px;
  padding: 6px 0;
  border-top: 1px solid var(--row-hover);
}
.problem-row:hover { background: var(--row-hover); }
.problem-row.done .q-text { text-decoration: line-through; color: var(--muted); }
.problem-row.filtered-out { display: none; }
.pattern.filtered-out { display: none; }
details.topic.filtered-out { display: none; }

.problem-row input[type="checkbox"] { margin-top: 3px; }
.q-main { flex: 1; min-width: 0; }
.q-line { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.q-text { cursor: pointer; }
.q-text:hover { text-decoration: underline; }
a.q-text { color: var(--fg); }

.badge {
  font-size: 0.7rem;
  padding: 1px 7px;
  border-radius: 10px;
  color: #fff;
  white-space: nowrap;
}
.badge.Easy { background: var(--easy); }
.badge.Medium { background: var(--medium); }
.badge.Hard { background: var(--hard); }

.star-btn { background: none; border: none; cursor: pointer; font-size: 1rem; color: var(--muted); padding: 0; }
.star-btn.active { color: #e0a300; }
.notes-btn { background: none; border: none; cursor: pointer; font-size: 0.85rem; color: var(--muted); padding: 0; }

.detail-panel { font-size: 0.78rem; color: var(--muted); margin-top: 4px; display: none; }
.detail-panel.open { display: block; }
.detail-panel textarea {
  width: 100%;
  min-height: 40px;
  margin-top: 4px;
  font-family: inherit;
  font-size: 0.85rem;
  padding: 6px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--bg);
  color: var(--fg);
}

footer {
  text-align: center;
  font-size: 0.75rem;
  color: var(--muted);
  padding: 20px;
}