:root {
  --background: #f5f5f5;
  --surface: #ffffff;
  --text: #171717;
  --muted: #737373;
  --border: #dedede;
  --red: #bd3434;
  --green: #16784b;
  --green-soft: #e7f5ed;
  --button-text: #ffffff;
  --summary-hover: #fafafa;
  --status: #777777;
  --focus: #6aa9ff;
}

:root[data-theme="dark"] {
  --background: #121212;
  --surface: #1d1d1d;
  --text: #f2f2f2;
  --muted: #aaaaaa;
  --border: #393939;
  --red: #ff8b8b;
  --green: #74c69d;
  --green-soft: #20372b;
  --button-text: #121212;
  --summary-hover: #272727;
  --status: #aaaaaa;
  --focus: #8bb9ff;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --background: #121212;
    --surface: #1d1d1d;
    --text: #f2f2f2;
    --muted: #aaaaaa;
    --border: #393939;
  }
}

* {
  box-sizing: border-box;
}

html {
  min-width: 320px;
  scrollbar-gutter: stable;
}

body {
  min-height: 100svh;
  margin: 0;
  padding: clamp(24px, 6vw, 56px) clamp(16px, 5vw, 32px);
  color: var(--text);
  background: var(--background);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

main {
  width: min(100%, 520px);
  margin: 0 auto;
}

.page-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.theme-toggle {
  display: inline-flex;
  min-height: 36px;
  align-items: center;
  gap: 6px;
  padding: 0 10px;
  border: 1px solid var(--border);
  border-radius: 999px;
  color: var(--muted);
  background: var(--surface);
  font: inherit;
  font-size: 0.76rem;
  font-weight: 700;
  cursor: pointer;
}

.theme-toggle:hover {
  border-color: var(--text);
  color: var(--text);
}

.theme-toggle-icon {
  font-size: 1rem;
  line-height: 1;
}

.back-link {
  color: var(--text);
  font-size: 0.85rem;
  font-weight: 700;
  text-decoration: none;
}

.back-link:hover {
  text-decoration: underline;
}

h1 {
  margin: 42px 0 8px;
  font-size: 1.5rem;
  font-weight: 700;
}

.intro {
  margin: 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.topic-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 24px;
}

.completed-filter {
  display: inline-flex;
  flex: none;
  align-items: center;
  gap: 8px;
  color: var(--muted);
  cursor: pointer;
  font-size: 0.82rem;
  font-weight: 650;
}

.completed-filter input {
  width: 17px;
  height: 17px;
  margin: 0;
  accent-color: var(--green);
}

.topic-list {
  display: grid;
  gap: 28px;
}

.all-link {
  display: block;
  padding: 16px 18px;
  border: 1px solid var(--text);
  border-radius: 12px;
  color: var(--text);
  background: var(--surface);
  font-weight: 700;
  text-decoration: none;
}

.all-link:hover {
  color: var(--button-text);
  background: var(--text);
}

.level-section {
  overflow: hidden;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--surface);
}

.level-summary {
  display: flex;
  min-height: 58px;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 0 17px;
  cursor: pointer;
  list-style: none;
}

.level-summary::-webkit-details-marker {
  display: none;
}

.level-summary:hover {
  background: var(--summary-hover);
}

.level-title {
  font-size: 1rem;
  font-weight: 750;
}

.level-summary-meta {
  display: flex;
  align-items: center;
  gap: 13px;
}

.level-count {
  color: var(--muted);
  font-size: 0.78rem;
}

.level-indicator {
  display: grid;
  width: 24px;
  height: 24px;
  place-items: center;
  border: 1px solid var(--border);
  border-radius: 50%;
  color: var(--muted);
  font-size: 1rem;
  line-height: 1;
  transition: transform 160ms ease;
}

.level-section[open] .level-indicator {
  transform: rotate(45deg);
}

.topic-section-list {
  display: grid;
  gap: 10px;
  padding: 0 10px 10px;
}

.topic-link {
  display: block;
  padding: 18px;
  border: 1px solid var(--border);
  border-radius: 12px;
  color: var(--text);
  background: var(--surface);
  text-decoration: none;
}

.level-section[open] .level-summary {
  border-bottom: 1px solid var(--border);
}

.level-section[open] .topic-section-list {
  padding-top: 10px;
}

.topic-link:hover {
  border-color: var(--text);
}

.topic-link.favorite {
  border-color: var(--green);
}

.favorite-mark {
  display: inline-flex;
  margin-top: 10px;
  color: var(--green);
  font-size: 0.74rem;
  font-weight: 750;
}

.topic-title {
  display: block;
  margin-bottom: 5px;
  font-weight: 700;
}

.topic-description {
  display: block;
  color: var(--muted);
  font-size: 0.85rem;
  line-height: 1.4;
}

.topic-status {
  display: block;
  margin-top: 0.35rem;
  color: var(--status);
  font-size: 0.82rem;
}

.topic-progress {
  display: inline-flex;
  margin-top: 10px;
  padding: 4px 8px;
  border-radius: 999px;
  color: var(--muted);
  background: var(--background);
  font-size: 0.76rem;
  font-weight: 750;
}

.topic-progress.perfect {
  color: var(--green);
  background: var(--green-soft);
}

.topic-progress.completed {
  color: var(--text);
}

.empty,
.loading,
.error {
  margin: 0;
  color: var(--muted);
  font-size: 0.85rem;
}

.level-section > .empty {
  padding: 14px 17px;
}

.error {
  color: var(--red);
}

a:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 3px;
}

summary:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: -3px;
}

@media (max-width: 430px) {
  .topic-toolbar {
    align-items: flex-start;
    flex-direction: column;
    gap: 12px;
  }
}

[hidden] {
  display: none !important;
}