:root {
  --trainer-bg: #f8f8f5;
  --trainer-panel: #ffffff;
  --trainer-border: #d8d2c4;
  --trainer-muted: #6a655c;
  --trainer-text: #1f1f1d;
  --trainer-blue: #2454b8;
  --trainer-blue-dark: #183f8f;
  --trainer-green: #147a3f;
  --trainer-red: #b3261e;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  max-width: 860px;
}

button {
  font: inherit;
}

.page-shell {
  margin: 0 auto;
}

.page-header {
  margin-bottom: 2.2rem;
  text-align: center;
}

.page-header h1 {
  margin-bottom: 0.2rem;
}

.explanation {
  margin-top: 1.5rem;
}

.explanation h2,
.trainer-section h2 {
  margin-top: 2rem;
}

.explanation p {
  line-height: 1.72;
}

.explanation pre {
  max-width: 100%;
  overflow-x: auto;
  border-radius: 6px;
}

.explanation code {
  white-space: pre;
}

.trainer-section {
  margin: 2.4rem 0;
  padding: 1.2rem 0;
  border-top: 1px solid var(--trainer-border);
  border-bottom: 1px solid var(--trainer-border);
}

.trainer-card {
  width: min(720px, 100%);
  margin: 1rem auto 0;
  padding: 1.35rem;
  background: var(--trainer-bg);
  border: 1px solid var(--trainer-border);
  border-radius: 8px;
  color: var(--trainer-text);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.06);
}

.header {
  margin-bottom: 1rem;
  text-align: center;
}

.header h2 {
  margin: 0;
  font-size: 1.45rem;
}

.header p {
  margin: 0.3rem 0 0;
  color: var(--trainer-muted);
  font-size: 0.95rem;
}

.date-display {
  margin: 1.1rem 0 1.3rem;
  text-align: center;
  font-family: "Latin Modern Mono", "SFMono-Regular", ui-monospace, Menlo, monospace;
  font-size: clamp(2.2rem, 7vw, 4rem);
  font-weight: 700;
  line-height: 1;
}

.answer-grid {
  display: grid;
  grid-template-columns: repeat(7, minmax(0, 1fr));
  gap: 0.45rem;
}

.answer-button,
.control-button {
  min-height: 2.7rem;
  padding: 0.35rem 0.55rem;
  border: 1px solid var(--trainer-border);
  border-radius: 6px;
  background: var(--trainer-panel);
  color: var(--trainer-text);
  font-weight: 700;
  cursor: pointer;
  transition:
    transform 120ms ease,
    border-color 120ms ease,
    background 120ms ease;
}

.answer-button:hover,
.control-button:hover {
  background: #f1efe8;
  border-color: #9f9786;
  transform: translateY(-1px);
}

.answer-button:active,
.control-button:active {
  transform: translateY(0);
}

.answer-button[disabled] {
  cursor: default;
  opacity: 0.55;
  transform: none;
}

.feedback {
  min-height: 2rem;
  margin: 1rem 0;
  text-align: center;
  color: var(--trainer-muted);
  font-weight: 700;
}

.feedback.correct {
  color: var(--trainer-green);
}

.feedback.wrong {
  color: var(--trainer-red);
}

.controls {
  display: grid;
  grid-template-columns: 1fr 1.35fr 1fr;
  gap: 0.55rem;
  margin-bottom: 0.9rem;
}

.control-button.primary {
  background: var(--trainer-blue);
  border-color: var(--trainer-blue);
  color: #ffffff;
}

.control-button.primary:hover {
  background: var(--trainer-blue-dark);
}

.solution {
  min-height: 11rem;
  max-height: 19rem;
  overflow: auto;
  margin: 0;
  padding: 1rem;
  background: #fffffb;
  border: 1px solid var(--trainer-border);
  border-radius: 6px;
  color: var(--trainer-text);
  font-size: 0.92rem;
  line-height: 1.55;
}

.solution-title {
  margin-bottom: 0.8rem;
  text-align: center;
  font-weight: 700;
}

.solution-section {
  padding: 0.75rem 0;
  border-top: 1px solid #e6e0d2;
}

.solution-section:first-of-type {
  border-top: 0;
  padding-top: 0;
}

.solution-section h2 {
  margin: 0 0 0.45rem;
  font-size: 0.85rem;
  text-transform: uppercase;
}

.solution-section p {
  margin: 0.35rem 0;
  color: var(--trainer-muted);
}

.target-date {
  color: var(--trainer-text) !important;
  font-family: "Latin Modern Mono", "SFMono-Regular", ui-monospace, Menlo, monospace;
  font-size: 1.3rem;
  font-weight: 700;
}

.formula,
.anchor-grid,
.month-grid {
  font-family: "Latin Modern Roman", "Times New Roman", Times, serif;
}

.formula {
  margin: 0.45rem 0;
  padding: 0.55rem 0.65rem;
  overflow-x: auto;
  background: #f5f2ea;
  border: 1px solid #e2dacb;
  border-radius: 6px;
}

.formula-stack {
  display: grid;
  gap: 0.45rem;
}

.formula-stack .formula {
  margin: 0;
}

.final-formula {
  border-color: #b7c6e8;
  background: #edf3ff;
  font-weight: 700;
}

.floor {
  font-weight: 700;
}

.anchor-grid {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.35rem 0.8rem;
  margin: 0.55rem 0;
  padding: 0.7rem;
  background: #f5f2ea;
  border-radius: 6px;
}

.anchor-grid span {
  color: var(--trainer-muted);
}

.month-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 0.45rem;
  margin: 0.6rem 0;
}

.month-grid span {
  padding: 0.45rem;
  border-radius: 6px;
  background: #f5f2ea;
  text-align: center;
}

.month-grid .current-month {
  background: #edf3ff;
  border: 1px solid #b7c6e8;
  font-weight: 700;
}

.stats {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 0.45rem;
  margin-top: 0.9rem;
  color: var(--trainer-muted);
  text-align: center;
  font-size: 0.9rem;
}

.stats span {
  padding: 0.55rem 0.45rem;
  background: #fffffb;
  border: 1px solid #e2dacb;
  border-radius: 6px;
}

.stats strong {
  color: var(--trainer-text);
}

@media (max-width: 640px) {
  .trainer-card {
    padding: 1rem;
  }

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

  .controls,
  .stats {
    grid-template-columns: 1fr;
  }

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