*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family:
    -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: #f5f5f5;
  color: #222;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 2rem 1rem;
}

.container {
  width: 100%;
  max-width: 600px;
}

h1 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 0.25rem;
  text-align: center;
}

.subtitle {
  text-align: center;
  color: #666;
  font-size: 0.95rem;
  margin-bottom: 2rem;
}

.card {
  background: #fff;
  border-radius: 12px;
  padding: 1.75rem;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
  margin-bottom: 1.5rem;
}

.inputs-label {
  font-size: 0.85rem;
  font-weight: 600;
  color: #555;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.75rem;
}

.inputs-row {
  display: flex;
  gap: 0.75rem;
  margin-bottom: 1.25rem;
}

.num-wrap {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.35rem;
}

.num-wrap label {
  font-size: 0.75rem;
  color: #888;
  font-weight: 500;
}

.num-input {
  width: 100%;
  padding: 0.6rem 0.5rem;
  font-size: 1.4rem;
  font-weight: 700;
  text-align: center;
  border: 2px solid #e0e0e0;
  border-radius: 8px;
  background: #fafafa;
  transition: border-color 0.15s;
}

.num-input:focus {
  outline: none;
  border-color: #4a6cf7;
  background: #fff;
}
.num-input.invalid {
  border-color: #e05252;
}

.btn-solve {
  width: 100%;
  padding: 0.8rem;
  font-size: 1rem;
  font-weight: 600;
  background: #4a6cf7;
  color: #fff;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition:
    background 0.15s,
    transform 0.1s;
}

.btn-solve:hover {
  background: #3a5ce5;
}
.btn-solve:active {
  transform: scale(0.98);
}

/* Results */

.results-card {
  background: #fff;
  border-radius: 12px;
  padding: 1.75rem;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
}

.results-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: 1rem;
}

.results-title {
  font-size: 1rem;
  font-weight: 600;
}

.results-meta {
  font-size: 0.82rem;
  color: #888;
}

.no-solution {
  text-align: center;
  color: #888;
  font-size: 0.95rem;
  padding: 1rem 0;
}

/* Idea groups (identity level) */

details.idea {
  margin-bottom: 0.5rem;
  border: 1px solid #e8eaf6;
  border-radius: 8px;
  overflow: hidden;
}

details.idea > summary {
  cursor: pointer;
  list-style: none;
  padding: 0.65rem 0.9rem;
  background: #f0f2ff;
  display: flex;
  align-items: flex-start;
  gap: 0.5rem;
  user-select: none;
  font-size: 0.88rem;
}

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

details.idea > summary .arrow {
  font-size: 0.6rem;
  color: #4a6cf7;
  transition: transform 0.15s;
  flex-shrink: 0;
}

details.idea[open] > summary {
  background: #e8eaf6;
}
details.idea[open] > summary .arrow {
  transform: rotate(90deg);
}

.summary-body {
  display: flex;
  flex-direction: column;
  flex: 1;
  min-width: 0;
  gap: 0.15rem;
}

details.idea > summary code,
details.subgroup > summary code {
  font-family:
    "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  font-size: 0.875rem;
  color: #1a1a2e;
  font-weight: 600;
  word-break: break-word;
  min-width: 0;
}

details.idea > summary .idea-count {
  font-size: 0.75rem;
  color: #888;
}

.idea-body {
  padding: 0.5rem 0.75rem 0.75rem;
}

/* Symbolic subgroups */

details.subgroup {
  margin-top: 0.4rem;
  border: 1px solid #eef0fb;
  border-radius: 6px;
  overflow: hidden;
}

details.subgroup > summary {
  cursor: pointer;
  list-style: none;
  padding: 0.45rem 0.75rem;
  background: #f7f8ff;
  display: flex;
  align-items: flex-start;
  gap: 0.5rem;
  font-size: 0.84rem;
  user-select: none;
}

details.subgroup > summary::-webkit-details-marker {
  display: none;
}
details.subgroup[open] > summary {
  background: #eef0fb;
}
details.subgroup[open] > summary .arrow {
  transform: rotate(90deg);
}

.sg-list {
  padding: 0.4rem 0.5rem 0.5rem;
}

/* Expression list */

.expr-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.expr-list li {
  font-family:
    "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  font-size: 0.875rem;
  padding: 0.4rem 0.65rem;
  background: #f7f8ff;
  border-radius: 5px;
  border-left: 3px solid #4a6cf7;
  color: #1a1a2e;
}

.hidden {
  display: none;
}

footer {
  margin-top: 2rem;
  font-size: 0.8rem;
  color: #aaa;
  text-align: center;
}

footer a {
  color: #aaa;
}

.page-nav {
  display: flex;
  gap: 0.25rem;
  margin-bottom: 1.5rem;
}
.page-nav a {
  padding: 0.4rem 0.9rem;
  border-radius: 20px;
  font-size: 0.85rem;
  font-weight: 600;
  color: #888;
  text-decoration: none;
  background: #ebebeb;
  transition:
    background 0.15s,
    color 0.15s;
}
.page-nav a:hover {
  background: #ddd;
  color: #444;
}
.page-nav a.active {
  background: #4a6cf7;
  color: #fff;
}

@media (max-width: 400px) {
  .num-input {
    font-size: 1.1rem;
    padding: 0.5rem 0.25rem;
  }
}