:root {
  color-scheme: light;
  --color-background: #f3f1eb;
  --color-card: #fffefa;
  --color-text: #17262d;
  --color-muted: #5d6b70;
  --color-border: #cdd4d2;
  --color-primary: #103f50;
  --color-primary-strong: #153e50;
  --color-primary-soft: #e3eef1;
  --color-focus: #b97800;
  --color-success: #246a4b;
  --color-success-soft: #e2f1e8;
  --color-review: #91501e;
  --color-review-soft: #faead9;
  --color-code: #132129;
  --shadow-card: 0 12px 30px rgb(35 54 61 / 9%);
  --radius-large: 18px;
  --radius-small: 10px;
}

* {
  box-sizing: border-box;
}

html {
  background: var(--color-background);
}

body {
  margin: 0;
  min-width: 0;
  background: var(--color-background);
  color: var(--color-text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans SC", sans-serif;
  font-size: 1rem;
  line-height: 1.6;
  overflow-wrap: anywhere;
}

button,
input,
select {
  max-width: 100%;
  color: inherit;
  font: inherit;
}

button {
  min-height: 44px;
  padding: 0.65rem 0.9rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-small);
  background: var(--color-card);
  cursor: pointer;
  font-weight: 700;
  line-height: 1.25;
  text-align: left;
  touch-action: manipulation;
}

button:hover {
  border-color: var(--color-primary);
  background: var(--color-primary-soft);
}

button:active {
  transform: translateY(1px);
}

button:disabled {
  cursor: not-allowed;
  opacity: 0.52;
  transform: none;
}

input,
select {
  width: 100%;
  min-width: 0;
  min-height: 44px;
  padding: 0.65rem 0.75rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-small);
  background: #ffffff;
  font-size: 16px;
}

input::placeholder {
  color: #657277;
}

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

[hidden] {
  display: none !important;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

#app-shell {
  width: min(100% - 24px, 760px);
  min-width: 0;
  margin: 0 auto;
  padding: 1.5rem 0 3rem;
}

#library-view,
#library-content,
#group-view,
#card-view,
.topic-shelf,
.card-front,
.card-answer {
  min-width: 0;
}

#library-view > header,
#group-view > header,
#card-view > header {
  margin-bottom: 1.1rem;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1,
h2,
h3 {
  color: var(--color-text);
  line-height: 1.2;
}

h1 {
  margin-bottom: 0.45rem;
  font-size: clamp(1.8rem, 8vw, 2.55rem);
  letter-spacing: -0.035em;
}

h2 {
  margin-bottom: 0.45rem;
  font-size: 1.3rem;
}

h3 {
  margin-bottom: 0.45rem;
  font-size: 1.05rem;
}

header p,
.topic-shelf > p {
  color: var(--color-muted);
}

.source-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.55rem;
  margin-bottom: 0.8rem;
}

.difficulty-badge {
  padding: 0.18rem 0.55rem;
  border-radius: 999px;
  background: var(--color-primary-soft);
  color: var(--color-primary);
  font-size: 0.85rem;
  font-weight: 800;
}

.source-link {
  color: var(--color-primary);
  font-weight: 800;
  text-underline-offset: 0.2em;
}

#filter-form {
  display: grid;
  min-width: 0;
  gap: 0.45rem;
  margin: 1.25rem 0;
  padding: 1rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-large);
  background: var(--color-card);
}

#filter-form label {
  margin-top: 0.35rem;
  font-size: 0.84rem;
  font-weight: 800;
  letter-spacing: 0.02em;
}

#filter-form label:first-child {
  margin-top: 0;
}

#filter-form button {
  margin-top: 0.45rem;
  text-align: center;
}

.topic-shelf,
#group-view,
#card-view {
  padding: 1.1rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-large);
  background: var(--color-card);
  box-shadow: var(--shadow-card);
}

.topic-shelf {
  border-top: 5px solid var(--color-primary);
}

.topic-reference {
  margin: 1rem 0;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-small);
  background: #f7f8f5;
}

.topic-reference summary {
  display: flex;
  min-height: 44px;
  padding: 0.65rem 0.8rem;
  align-items: center;
  cursor: pointer;
  font-weight: 750;
}

.topic-reference[open] summary {
  border-bottom: 1px solid var(--color-border);
}

pre {
  max-width: 100%;
  min-width: 0;
  margin: 0.8rem 0;
  padding: 0.9rem;
  overflow-x: auto;
  border-radius: var(--radius-small);
  background: var(--color-code);
  color: #edf4f4;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.82rem;
  line-height: 1.55;
  overscroll-behavior-inline: contain;
  white-space: pre;
}

.topic-reference pre {
  margin: 0;
  border-radius: 0 0 var(--radius-small) var(--radius-small);
}

code {
  font-family: inherit;
}

.traversal-groups,
.group-card-list {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 0.7rem;
  margin: 1rem 0;
  padding: 0;
  list-style: none;
}

.traversal-groups button,
.group-card-list button {
  width: 100%;
  min-width: 0;
}

.traversal-groups button {
  display: grid;
  gap: 0.2rem;
  padding: 0.85rem 1rem;
  border-left: 4px solid var(--color-primary);
}

.traversal-groups button span:first-child {
  color: var(--color-primary-strong);
  font-size: 1.05rem;
}

.traversal-groups button span:last-child,
.card-entry button > span:nth-child(2) {
  color: var(--color-muted);
  font-size: 0.82rem;
  font-weight: 600;
}

.card-entry button {
  display: grid;
  gap: 0.35rem;
  padding: 0.9rem;
}

.card-entry button > span:first-child {
  font-size: 1rem;
}

.status-badge,
[data-status] {
  display: inline-flex;
  width: fit-content;
  min-height: 28px;
  margin: 0;
  padding: 0.2rem 0.55rem;
  align-items: center;
  border: 1px solid var(--color-border);
  border-radius: 999px;
  background: #f1f3f1;
  color: var(--color-muted);
  font-size: 0.78rem;
  font-weight: 800;
  line-height: 1.2;
}

[data-status="known"] {
  border-color: #9ec8b1;
  background: var(--color-success-soft);
  color: var(--color-success);
}

[data-status="review"] {
  border-color: #ddb58c;
  background: var(--color-review-soft);
  color: var(--color-review);
}

#group-view > header > button,
#card-view > header > button {
  margin-bottom: 1rem;
  border-color: transparent;
  background: var(--color-primary-soft);
  color: var(--color-primary-strong);
}

.card-front,
.card-answer {
  margin-top: 1rem;
  padding: 1rem;
  border: 1px solid var(--color-border);
  border-radius: 14px;
}

.card-front {
  background: #fbfaf5;
}

.card-front > button {
  width: 100%;
  margin-top: 0.75rem;
  background: var(--color-primary);
  color: #ffffff;
  text-align: center;
}

.card-front > button:hover {
  background: var(--color-primary-strong);
}

.card-front section {
  padding-top: 0.9rem;
  border-top: 1px solid var(--color-border);
}

.card-front ol,
.card-answer ul {
  padding-left: 1.3rem;
}

.card-front li,
.card-answer li {
  margin-bottom: 0.45rem;
}

.card-answer {
  border-color: #a9c8d2;
  background: #f5fafb;
}

.card-answer dl {
  display: grid;
  grid-template-columns: minmax(0, 7.5rem) minmax(0, 1fr);
  gap: 0.35rem 0.7rem;
  margin: 1rem 0;
}

.card-answer dt {
  color: var(--color-muted);
  font-weight: 800;
}

.card-answer dd {
  min-width: 0;
  margin: 0;
}

.card-actions {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 0.6rem;
  margin-top: 1rem;
}

.card-actions button {
  text-align: center;
}

.card-actions [data-action="mark-known"] {
  border-color: #83b89d;
  background: var(--color-success-soft);
  color: var(--color-success);
}

.card-actions [data-action="mark-review"] {
  border-color: #d6a878;
  background: var(--color-review-soft);
  color: var(--color-review);
}

#empty-state,
#status-notice {
  margin: 1rem 0 0;
  padding: 0.9rem 1rem;
  border-radius: var(--radius-small);
  font-weight: 700;
}

#empty-state {
  border: 1px dashed var(--color-border);
  background: var(--color-card);
  color: var(--color-muted);
}

#status-notice {
  border: 1px solid #a9c8d2;
  background: var(--color-primary-soft);
  color: var(--color-primary-strong);
}

@media (min-width: 700px) {
  #app-shell {
    width: min(100% - 40px, 760px);
    padding-top: 2.5rem;
  }

  #filter-form {
    grid-template-columns: minmax(8rem, 0.38fr) minmax(0, 1fr);
    gap: 0.55rem 1rem;
    align-items: center;
  }

  #filter-form label,
  #filter-form label:first-child,
  #filter-form button {
    margin-top: 0;
  }

  #filter-form button {
    grid-column: 2;
    justify-self: start;
  }

  .topic-shelf,
  #group-view,
  #card-view {
    padding: 1.5rem;
  }

  .traversal-groups {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .group-card-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .card-actions {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}