:root {
  --bg: #f6f8fc;
  --panel: #ffffff;
  --line: #d7deea;
  --text: #10223a;
  --accent: #2563eb;
  --accent-soft: #e9f0ff;
  --ok-soft: #e7fbef;
  --warn-soft: #fff7dd;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", Tahoma, sans-serif;
  background: radial-gradient(circle at 10% 0%, #eef3ff 0%, var(--bg) 45%);
  color: var(--text);
}

.app {
  max-width: 1200px;
  margin: 0 auto;
  padding: 18px;
}

.panel {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 16px;
  margin-bottom: 14px;
  box-shadow: 0 8px 24px rgba(16, 34, 58, 0.05);
}

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

h1 {
  margin-bottom: 10px;
  font-size: 28px;
}

h2 {
  margin-bottom: 12px;
  font-size: 20px;
}

h3 {
  margin-bottom: 8px;
  font-size: 16px;
}

p {
  margin: 0;
  line-height: 1.58;
}

.controls {
  display: grid;
  gap: 10px;
}

label {
  display: flex;
  flex-direction: column;
  gap: 6px;
  font-weight: 600;
}

select,
button {
  font: inherit;
}

select {
  width: 100%;
  max-width: 420px;
  padding: 8px 10px;
  border: 1px solid var(--line);
  border-radius: 10px;
}

button {
  width: fit-content;
  padding: 10px 16px;
  border-radius: 10px;
  border: 1px solid #1d4ed8;
  background: var(--accent);
  color: #fff;
  font-weight: 700;
  cursor: pointer;
}

button:hover {
  filter: brightness(1.05);
}

.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 10px;
}

.chip {
  display: inline-flex;
  align-items: center;
  border: 1px solid #bfd0f5;
  background: #edf3ff;
  color: #17325f;
  border-radius: 999px;
  padding: 4px 10px;
  font-size: 13px;
  font-weight: 700;
}

.chip.alt {
  border-color: #9fdab5;
  background: var(--ok-soft);
  color: #085b39;
}

.chip.warn {
  border-color: #ead07a;
  background: var(--warn-soft);
  color: #6a5100;
}

.task-text,
.program-wrap,
.solution,
.theory-wrap {
  line-height: 1.55;
}

.task-text p + p,
.theory-wrap p + p,
.program-wrap p + p {
  margin-top: 10px;
}

.theory-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin-top: 12px;
}

.theory-card {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #f8fbff;
  padding: 12px;
}

.theory-card p {
  margin-bottom: 8px;
}

.theory-card p:last-child {
  margin-bottom: 0;
}

.bullet-list {
  margin: 0;
  padding-left: 20px;
}

.bullet-list li {
  margin-bottom: 6px;
}

.bullet-list li:last-child {
  margin-bottom: 0;
}

.note-box,
.answer-box {
  margin-top: 10px;
  border-radius: 10px;
  padding: 10px 12px;
  border: 1px solid #bfd0f5;
  background: #edf3ff;
}

.answer-box {
  border-color: #9fdab5;
  background: var(--ok-soft);
  font-weight: 700;
}

.program-table-wrap,
.solution-table-wrap {
  overflow: auto;
  margin-top: 10px;
}

table {
  border-collapse: collapse;
  width: 100%;
}

th,
td {
  border: 1px solid var(--line);
  padding: 8px 10px;
  text-align: left;
  vertical-align: top;
}

th {
  background: var(--accent-soft);
  font-weight: 700;
}

.compact-table {
  min-width: 420px;
}

.transition-table {
  min-width: 560px;
}

.command-table {
  min-width: 420px;
}

.program-caption,
.small-muted {
  color: #4d6185;
  font-size: 14px;
}

.program-caption {
  margin-bottom: 8px;
}

.small-muted {
  margin-top: 8px;
}

code {
  font-family: "Consolas", "DejaVu Sans Mono", monospace;
  background: #eef3ff;
  border-radius: 6px;
  padding: 1px 6px;
}

.solution details {
  border: 1px solid var(--line);
  border-radius: 10px;
  background: #f8fbff;
  padding: 10px 12px;
}

.solution summary {
  cursor: pointer;
  font-weight: 700;
}

.solution ol {
  margin: 10px 0 0 20px;
  padding: 0;
}

.solution li {
  margin-bottom: 8px;
}

.python-wrap {
  margin-top: 10px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: #f8fbff;
  overflow: auto;
}

pre {
  margin: 0;
  padding: 12px;
  font-family: "Consolas", "DejaVu Sans Mono", monospace;
  font-size: 12px;
  line-height: 1.45;
}

.formula-line {
  margin-top: 8px;
  font-weight: 600;
}

@media (max-width: 860px) {
  .theory-grid {
    grid-template-columns: 1fr;
  }
}